1
LITHUANIAN UNIVERSITY OF HEALTH SCIENCES
FACULTY OF MEDICINEDEPARTMENT OF NEUROLOGY
DIVYA EDAPPAZHATHIL
CHANGES IN BIOMARKERS OF DIURNAL RHYTHM IN
STROKE PATIENTS: A SCOPING LITERATURE REVIEW
MIEGO IR BŪDRAVIMO RITMĄ ATSPINDINČIŲ BIOŽYMENŲ
POKYČIAI TARP GALVOS SMEGENŲ INSULTĄ PATYRUSIŲ
PACIENTŲ: TEMINĖ- LITERATŪROS APŽVALGA
Submitted in partial fulfilment of the requirements for the degree of Master of Medicine
SUPERVISOR: PROF.KESTUTIS PETRIKONIS, MD, PhD CONSULTANT: EVELINA PAJEDIENE MD
2
TABLE OF CONTENT
ACKNOWLEDGMENT ... 3
CONFLICT OF INTEREST... 4
APPROVAL OF ETHICS COMMITTEE ... 4
KEYWORDS ... 5 ABBREVATIONS... 5 ABSTRACT ... 6 INTRODUCTION... 9 RESEARCH METHODOLOGY ... 12 RESULT... 14 DISCUSSION ... 25 CONCLUSION ... 28 REFERENCES... 29
3
ACKNOWLEDGMENT
I express my sincere gratitude to the head of department of Neurology, Prof. habil. Dr. Daiva Rastenytė for giving me an opportunity to write my thesis.
I would like to thank my supervisor prof. Kęstutis Petrikonis for his invaluable support, advice and encouragement throughout my work.
This thesis would not have been possible without the support from my consultant Dr. Evelina Pajėdienė. I am extremely thankful for her knowledge, valuable suggestions, comments and
4
CONFLICT OF INTEREST
The authors report no conflicts of interest. The author alone is responsible for the content and writing of this article.
APPROVAL OF ETHICS COMMITTEE
5
KEYWORDS
Biological rhythm; Circadian rhythm; diurnal rhythm; stroke; melatonin; cortisol; biomarker; core body temperature; actigraphy; temperature target therapy; clock gene; ischemic stroke; intradaily variability; scoping review; systematic review; randomised controlled trial; cohort; exogenous melatonin; animal studies; chronography; diurnal pattern; diurnal disruption; internal clock; circadian disruption; neurodegenerative; chronotype; rhythm fragmentation.
ABBREVATIONS AIS- acute ischaemic stroke
BP-blood pressure
CBFV-cerebral blood flow velocity CBT-core body temperature
CU-indoor lighting
GCS- Glasgow coma scale HPA-hypothalamus pituitary axis HS- haemorrhagic stroke
IV-intradaily variability IS-interdaily stability IS- ischaemic stroke IU- naturalistic lighting ICU- intensive care unit
MEQ-Morning evening questionnaire MCTQ- Munich chronotype questionnaire
MSFsc -mid-sleep on work-free days corrected for sleep deficit on workdays MMCAI- Middle cerebral artery infarction
NIHSS- National Institutes of Health Stroke Scale PF-plasma fibrinogen
PSD- Post stroke depression PS- post stroke
PVS -paraventricular nucleus of hypothalamus
SAH- Subarachnoid haemorrhage SP-stroke patients
SCN- Suprachiasmatic nucleus TIA- transient Ischaemic attack
6
ABSTRACT
AIM
The proposed review aims to synthesize existing evidence on the changes in diurnal rhythm in stroke patients, how these changes can be assessed and its relevance in improving clinical outcome.
OBJECTIVE
1. To review articles establishing changes of metabolic, genetic and instrumental biomarkers of diurnal rhythm in stroke patients.
2. To review and discuss the clinical impact of diurnal rhythm changes and future therapeutic targets for stroke patients.
3. To review and discuss methodological aspects and future implication perspectives of the investigated biomarkers.
METHODS
Standard scoping literature review methodology was followed to select and extract data from different studies done on changes in biomarkers of diurnal rhythm in stroke patients. Electronic databases PubMed, Cochrane Library, MEDLINE, were searched for a wide range of keywords including ‘biomarker’, ‘stroke’, ‘diurnal rhythm’ up to February 2020.The search was carried out in a systematic hierarchical approach; firstly systematic reviews and meta-analyses published on disruptions in diurnal rhythm in stroke were searched and assessed. Following that, all primary studies post- dating systematic review and meta-analyses addressing the research objectives were searched for and identified. 396 articles were identified in the initial assessment. Duplicates were removed, title and abstract screened and 82 articles were selected. Full text of potentially relevant articles was assessed against the eligibility criteria and 30 articles were selected for the review. Finally, data reporting in a narrative synthesis and the results presentation in the form of table was undertaken.
RESULT
A systematic search of publications from databases and additional resources identified a total of 396 articles out of which 30 articles met the eligibility criteria. All articles were assessed, the findings were then further summarised into tables and reviewed in a narrative form. All stroke patients studied herein showed disruption in circadian rhythm. Studies (n=8) utilising Cortisol and melatonin were observed to show changes in the acute phase of stroke up to 3 months. Core body temperature (n=3) was reported to be elevated after stroke. Changes in actigraphy (n=2), blood pressure (n=1), chronotype (n=1), clock gene(n=1) were also reported in stroke patients. 11 studies reported clinical impacts of disrupted circadian rhythms which included higher mortality rate, poor functional outcome, increased infarct size, depression and insomnia. Administration of melatonin (n=2), temperature targeted management(n=1) and interventional use of light therapy(n=1) has shown beneficiary effects in animals and stroke patients. Stroke exhibits a temporal pattern in occurrence with the highest peak in the morning
7
which could be in association to the changes in endogenous biomarkers of diurnal rhythm (n=7).
CONCLUSION
This scoping literature review revealed that stroke causes disruption of diurnal rhythm. Acute phase of stroke was marked with significant changes in endogenous biomarkers of diurnal rhythm including cortisol, melatonin, Core body temperature. Temperature target management, exogenous melatonin administration and use of naturalistic light showed beneficiary effects in re-establishing the diurnal rhythm and improving functional outcome. Serum cortisol, melatonin, CBT, actigraphy can be used as reliable biomarkers for studying circadian rhythm changes in stroke.
8
Šia literatūros apžvalga siekama įvertinti cirkadinio bei paros ritmo pokyčius, pasireiškiančius susirgus galvos smegenų insultu, bei jų įtaką neurologinėms išeitims po insulto. Literatūros analizės metu buvo vertinami moksliniai straipsniai, kuriuose pristatomi cirkadinius bei paros ritmus atspindinčių biožymenų, tokių kaip melatoninas, kortizolis, šerdinė kūno temperatūrą bei laikrodiniai genai, tyrimai. Iš 396 pirminį vertinimą atitikusių straipsnių, 30 iš jų buvo atrinkti tolesnei analizei.
Ryšį tarp cirkadinio bei paros ritmo ir galvos smegenų insulto patvirtino dauguma apžvelgtų studijų. Paros ritmo sutrikimai yra susiję su insulto sunkumu, didesnės apimties smegenų pažaida, blogesniu neurologinių funkcijų atsistatymu, didesniu mirštamumu, dažnesniu nemigos ir depresijos pasireiškimu.
Optimali kūno temperatūra, egzogeninio melatonino vartojimas ir gaunamos natūralios bei dirbtinės šviesos kiekio ir intensyvumo korekcijos padėjo veiksmingai atkurti tinkamą paros ritmą ir pagerinti ligos išeitis.
Kortizolio bei melatonino koncentracijos kraujyje įvertinimas, šerdinės kūno temperatūros svyravimai bei aktigrafija gali būti pakankamai patikimi biožymenys, tiriant cirkadinio bei paros ritmo pokyčius galvos smegenų insultą patyrusiems pacientams. Planuojant ateities mokslinius ir klinikinius tyrimus, tikslinga tobulinti metodiką, leidžiančią minėtus biožymenis matuoti paprasčiau, efektyviau ir ilgesnį laiką.
9
INTRODUCTION
Biological rhythms are natural synchronized cyclic patterns shown by an organism as a response to its own body’s stimulus [1]. A diurnal rhythm is a biological rhythm that works in synchronization with the day and night cycle. This, however, may or may not be a circadian rhythm. It is attributed as an important source of biomarker variability. These rhythms are principally controlled by the suprachiasmatic nucleus (SCN) which is located in the anterior part of the hypothalamus. Photic input from intrinsically photosensitive retinal ganglion cells (ipRGCs) is sent to neurons in the SCN through the retinothalamic tract. The non-photic signals sent from other parts of the brain also helps to modulate the circadian rhythm. The integration of both these inputs together drive the cycle for the master clock rhythm.
Although SCN acts as a master clock, it has been recognized that circadian rhythms are also generated at a molecular level within almost every cell of the body by expression of ‘clock’ genes [2]. Such clock genes are present in SCN as well as other cells. SCN oscillations are produced by rhythmic expression of clock genes through an intracellular transcriptional/translational negative feedback loop [1,2,6] (figure 1).Several genes corresponding to circadian rhythmicity have been studied and eight of these are understood as the core genes: Period- PER1,2 and 3, Cryptochrome- CRY1 and CRY2, and the transcription factors Clock, Bmal1 and Npas2 [2,6,13] A multitude of physiological functions are associated with the circadian rhythm generated by the SCN and at the peripheral level.
Figure 1. Clock gene feedback loop in SCN SCN- Suprachiasmatic nucleus; Alavoodin et al 2009 [32]
Stroke is one of the leading causes of death and disabilities in the world. Studies have shown that stroke destabilizes the diurnal rhythm [3,9,11,14,23,26-29,39]. Whether these disruptions are a cause or consequence of stroke is not yet fully understood. Stroke study reports have proven a time-of day variation in stroke susceptibility [11,17-21,25]. In recent times, studies about biological rhythms and how they are affected in stroke and other diseases have gained more interest as researchers have been identifying potential role of these disruptions in determining the onset, severity, and frequency of stroke. Furthermore, understanding the effect
10
of these disruptions on the clinical outcome brings new light into new possible treatments and improve functional outcome of the patients.
Many biomarkers have been identified to in order to study the presence of diurnal rhythm disruptions in stroke like melatonin, cortisol, core body temperature. Melatonin is secreted from the Pineal gland under the control of SCN [6,32]. It is one of the most accurate markers of diurnal rhythm in humans. Adrenal secretion of cortisol shows a robust circadian rhythm. Alterations to HPA and melatonin has been associated with neurodegeneration.
Core body temperature (CBT)in humans tend to follow a 24-hour rhythm making it a significant biomarker in analysing the diurnal rhythms [8,49]. CBT increases during the daytime, reaching its peak in the late afternoon, in a period of 15:00-17:00 and decreases gradually with its the lowest values in the early morning hours. This diurnal pattern is attributed primarily with the autonomic nervous system due to the variability seen in thermal production and loss [8]. Melatonin acts on the hypothalamic thermoregulatory centre and has impacts on thermoregulation. Figure 2 shows the normal circadian rhythm of melatonin, cortisol and Core body temperature. Figure 3 is an example of disrupted circadian rhythm in melatonin and cortisol in acute ischemic stroke.
Figure 2. Normal circadian rhythm of melatonin, cortisol and Core body temperature [48].
Figure 3a. Melatonin in control vs AIS Figure 3b. Cortisol in control vs AIS [14]
11
Actigraphy has been used for analysing circadian rhythmicity in humans using nonparametric variables [23,39]. Actigraphy measures the rest-activity rhythm in humans by measuring the gross body movement using non-parametric variables. These variables are known as nonparametric variables because they are not associated to parameters of known function [23,39]. Rhythmic fragmentation and synchronisation in 24-hour rest-activity cycle is measured using intradaily variability (IV) and interdaily stability (IS). IV is the measurement of the fragmentation of the 24 hour rest-activity cycle, i.e.; it quantifies the transition or the shift between the periods of activity and rest.IS refers to the stability of the rhythm over days, it quantifies the similarity or the synchronization of the rhythm to the 24h day-night cycle [23]. Examples of varying stability and fragmentation of rhythms from the Rotterdam Study. are given below. These are activity plots of patients who participated in the study [38].
Figure 3. A) high stability low fragmentation B) high fragmentation C) low stability D) low
stability high fragmentation
Circadian disruptions are composed of impaired cortisol and thermoregulation rhythm, the reduction of melatonin levels, impaired expression of the CLOCK genes and rhythm fragmentations.
This scoping literature review aims to study the existing evidence on the disruptions of diurnal rhythm in stroke patients. Studies using melatonin, cortisol, clock genes and body temperature as biomarkers of diurnal rhythm in stroke patients will be reviewed and the findings will be analysed and discussed. The first part of the review will briefly summarise the temporal pattern seen in stroke occurrence as this could be a result of these rhythm changes. The changes in biomarkers, their clinical impact ad treatment will be reviewed after. Finally, future perspective of a biomarker-based diagnosis and treatment will be discussed.
12
RESEARCH METHODOLOGY AIM
The proposed review aims to synthesize existing evidence on the changes in diurnal rhythm in stroke patients, how these changes can be assessed and its relevance in improving clinical outcomes.
PRIMARY SEARCH
Relevant articles in the English language were identified by searching research databases including the following: PubMed, Cochrane, MEDLINE and other sources such as google scholar. Registers of clinical trials such as clinicaltrial.gov, International Standard Randomised Controlled Trials Number Database (ISRCTN) were also utilized in the primary search. The search was carried out in a systematic hierarchical approach; firstly systematic reviews and meta-analyses published on disruptions in diurnal rhythm in stroke were searched and assessed. Following that, all primary studies post- dating systematic review and meta-analyses addressing the research objectives were searched for and identified. 396 articles were identified in the initial assessment. Duplicates were removed, title and abstract screened and 82 articles were selected. Full text of potentially relevant articles were assessed against the eligibility criteria and 30 articles were selected for the review.
ELIGIBILITY CRITERIA Inclusion criteria
The following criteria were used for selecting articles for this review: Year of publication
Articles published between 2014 and 2020 February on changes in biomarkers of diurnal rhythm in stroke patients were selected.
Study design
Studies in full text published in English
Experimental studies designed as RCTs and non-randomized trials.
Observational studies done as a longitudinal cohort, case-control study, cross-sectional studies and database entry
Standard systematic reviews with more than 10 articles, meta-analyses. Studies that recruited 10 or more stroke patients.
Biomarker measurements done according to the current standards. Population
The population of interest was adult human above 18 years old and no upper limit, of any ethnicity, gender and animal studies.
Exclusion criteria
Articles with no primary data such as editorials, conference abstracts. Articles available only in abstract form
Unpublished Doctoral Dissertations, case reports;
13
DATA EXTRACTION
Relevant data were extracted from the selected articles in a standardized piloted data extraction form. For each study, eligible information pertaining for the review, as follows, but not limited to was extracted: study identification (Year of publication, author, Title) study characteristics (the type of study, sample-size, follow up, outcome variable) Participant characteristics (Stroke subtypes, 18 and over adults, animal studies).
DATA SYNTHESIS AND REPORTING
This scoping literature review and its findings are reported in the form of tables and presented in a narrative synthesis. The findings from this review will explore the potential implications on current and future clinical outcomes, therapeutic perspectives and also may highlight the areas for possible future research.
14
RESULT
Based on the search keywords, 237 studies were identified from PubMed, Cochrane and additional 158 records were identified through Google Scholar and from reference lists of published articles. Titles and abstracts were screened and 237 were selected out of which 30 full text articles were retrieved after assessing against eligibility criteria. Findings from the qualitative analysis has been summarised in Tables 1-5.
Figure 4. PRISMA flowchart of study selection. n refers to number of studies. Records identified through
database searching n = 237
Additional records identified through Google Scholar
n =158
Records after duplicates removed (n = 373) Records screened (n = 373) Records excluded (n =291) Full-text articles assessed for eligibility
(n =82)
Full-text articles excluded, with reasons
(n = 52)
Researches not published; n= 5 Doctoral dissertations,
conference articles, abstracts; n=38
Unable to access full text; n=6 Case reports; n=3
Studies included in qualitative synthesis
15 Temporal pattern in stroke occurrence
Prevalence of stroke has shown a circadian pattern with the highest rate of incidence in the morning. 7 studies have been analysed with a total of 4613 patients and the findings have been summarized in Table 1. Out of the 7 articles, 5 of them had classified stroke as ischemic, haemorrhagic types [11,18,20,21,25] while the other 2 followed TOAST classification [17,19]. Stroke exhibits a circadian pattern in occurrence with the highest peak in the late morning hours, between 06:00 am and 12:00 am and lowest in the evening hours. All studies (excluding [21]) concluded same findings in all subtypes of stroke, while [21] shows an increased occurrence of HS in the afternoon. Findings are summarised in Table 1.
Table 1. temporal pattern in stroke occurrence
AUTHOR, YEAR
AND REFEREN
CE
Stroke type and sample size 00:00-06:00 06:00-11:59 12:00-17:59 18:00-23:59 undetermined RESULT/ CONCLUSION Yong Seo et al 2014 [17] TIA=198, SVO= 398, LAA=551 CE=412, other=33, undetermined=32 4 189 664 661 533 - Prevalence of stroke occurrence peaked in the morning hours. (from 06:00-12:00) Fodor et al 2014[18] IS- 969, HS-94, SAH-20 IS-6.60% HS-8.51% SAH-10% IS-45.40% HS-55.31% SAH-40% IS-16.61% HS-17.02% SAH-20% IS-16% HS-12.76 % SAH-20% IS-15.38% HS-6.38% SAH-15%
All three types of stroke-IS, HS, SAH shows a circadian variation with highest incidence in the morning and lowest in the night hours. Yun et al 2015[19] LAA-256, SVO-276, CE-155, SOC/SUC-191, TIA-90 104 363 299 202 - Onset of stoke follows a circadian pattern with the highest occurrence between 06-12:00 Mohammed et al 2019 [20] IS=40 HS=27 IS=13 HS=4 IS=19 HS=13 IS=6 HS=6 IS=2 HS=4 - The occurrence stroke shows a circadian variation with highest occurrence from 6:00-12:00 am
16
IS- Ischemic stroke, HS- haemorrhagic stroke, SAH-subarachnoid haemorrhage, LAA- large artery
atherosclerosis, SVO-small vessel occlusion, TIA –transient ischemic attack, CE-cardioembolic, SOC-stroke of other causes, SUC-stroke of undetermined cause
Changes in biomarkers of diurnal rhythm in stroke patients
Cortisol and melatonin
Among studies measuring circadian biomarkers (n= 16), all studies reported significant changes in the normal values of the biomarkers. Studies using cortisol [9,11,14,26,28,29] reported an increase in cortisol levels following stroke. One study examined cortisol in 4-time intervals and reported significantly increased values in all the intervals compared to the control [11], while another study observed elevated cortisol when measured in the morning and in the afternoon along with absent rhythm [29]. Systematic review done by Barugh et al., reported significantly increased cortisol in the first 7 days after stroke [9].
It was observed that the acute phase of stroke was marked with decrease in melatonin [4,14,22]. Studies that evaluated melatonin and cortisol for 24 hours showed a loss in diurnal rhythm in secretion of these hormones [3,14,11,29]. Phase advanced rhythm of cortisol in conjunction with abnormal melatonin profile was reported in 24-hour analysis [14].
Shereen et al. [11] and Barugh et.al [9] reported a follow up of cortisol level in stroke patients in 3 months and found out that cortisol levels had normal values with a reappearance normal circadian rhythm indicating that these changes could be transient. Findings about changes in cortisol and melatonin are summarised in Table 2.
Body temperature
Changes in temperature within 24 hours after stroke have been observed in stroke patients. As hypothesized in several studies, all the observational studies have shown an increase in CBT during the acute phase of stroke [12,33,37]. One of the studies observed a mean patient body temperature within 48 hours of 37.5˚C with the highest temperature recorded 41.5 °C [12]; while another study that measured the temperature at the time of admission, day 1,2, and 3
Ginenus et al 2019 [21] IS=60, HS=56 IS=14 HS=14 IS-14 HS=20 IS=23 HS=15 IS=9 HS=7
- The onset of stroke shows a circadian pattern with a significant peak in the morning for HS and afternoon for IS Shereen et
al.,2019[11]
IS=60, HS=38 16 36 27 19 - Increased risk of
stroke in the morning hours with a peak b/w 06:00am and 12pm. Raj K et al 2015 [25] IS=247, HS=120 IS=73 HS=29 IS=100 HS=43 IS=58 HS=32 IS=16 HS=16 - The rate of occurrence of stroke was highest in the late morning 06:00-11:59h
17
revealed changes in temperature. Days one, two and three measured higher mean and peak body temperatures than on admission (p < 0.001 for all days) [33]. Subarachnoid haemorrhagic patient’s study revealed mean body temperature of 37.41 ± .05°C when measured from day 4 to 14 with the highest peak on day 5 which gradually decreased reaching lowest value on day 14 [37]. No studies measured the diurnal differences in temperature. Study reports are outlined in Table 3.
Actigraphy
2 studies were identified and utilised for evaluating circadian rhythm changes using actigraphy. [23,39]. Both the studies reported significant changes in circadian rhythm after stroke. In the study done by Zuurberg and colleagues, no rhythm fragmentation was seen in Lacunar infarcts but white matter lesions and microbleeds were significantly associated with rhythm fragmentation (measured with intradaily variability) in the 24h cycle [23]. One of the studies performed actigraphy by measuring IV between 1 and 60 mins rather than the conventional 60-minute sampling Mean IV (IVm) was calculated in each time interval and assessed. It was reported that IV in each interval was higher for the stroke patients. IVm was significantly higher than the control group. The IV calculated in one hour (IV60) showed no difference between 2 groups [39]. Both the studies revealed rhythm fragmentations in the 24-hour cycle in stroke patients. Findings from the review are summarised in Table 4.
Clock gene, Chronotype, Blood pressure
A systematic review reported that circadian genes have variable degree of expression throughout the day. The decreased expression can potentially be a risk factor for stroke occurrence [13].
Self-reported chronotype defined as Mid-sleep on work-free days corrected for sleep deficit on workdays (MSFsc) showed significant changes in stroke, especially in patients with more severe
strokes at up to 3 months after stroke. The impact of stroke on MSFsc was correlated with the internal time of stroke (InTstroke); the earlier the internal time of a stroke relative to MSFsc-before-stroke, the more MSFsc advanced after stroke. Strokes that occurred in the anterior circulation lead to delays of MSFsc, whereas strokes within the posterior circulation lead to advances of MSFsc [24].
Shereen and colleagues (2019) reported a variety of diurnal variations including blood pressure in stroke patients. 59 stroke patients had an abolished diurnal pattern of blood pressure with no nocturnal dipping [11] (Table 2).
Clinical impacts of circadian disruption in stroke patients
Clock gene
Out of 12 studies that explored clinical impact of circadian variations, one was animal study. Ischemic stroke was induced in 70 mice and at 4 different Zeitgeber time points with 6-hour difference intervals, Levels of PER1, Clock and Bmal1 were assessed. The group with increased level of PER1, Clock and Bmal1 showed decreased tissue injury, oedema formation and a better neurological deficit score. Stroke in the night times results in less severe neuronal damage with increased expression of circadian clock proteins [10].
18
Cortisol, Melatonin
2 studies reported a significant correlation between elevated cortisol levels and poor prognosis [9,28]. Patients who died within 7 days of stroke onset was reported to have serum cortisol as high as 1359.4 ± 256.8 nmol/l as against 624.9 ± 123.9 nmol/l in those who survived [28]. Study conducted by Zhang et al. (2016) revealed that stroke patients with depression had higher cortisol level than the stroke patients who did not have depression [29].
Decreased nocturnal melatonin was recorded in stroke patients with insomnia when compared with the non-insomnia group [22]. Melatonin level showed a positive correlation with NIHSS. The interaction factor melatonin × NIHSS shows a negative correlation with severity of insomnia (Insomnia Severity Index Score), quality of sleep (Pittsburgh Sleep Quality Index scores), and fatigue level of patients (Fatigue Severity Scale scores), but positive correlation with the Morningness and Eveningness Questionnaire score [22]. However, increased level of melatonin was reported to be associated with increased mortality rate in MMCAI [4]. Out of the 64 patients with MMCAI and a GCS score < 9, 32 patients who died within 30 days reported to have higher melatonin than the survivors (p< 0.001) [4].
There was a significant negative correlation established between MSFsc and NIHSS with the
difference in chronotype after stroke [24]. It was also speculated that patients with more severe stroke showed more changes in their sleep timing [24]. Findings in Table 2.
Blood pressure
Shereen and colleagues (2019) showed about 66% of patients presented with reverse dipper pattern, and 62% of patients with extreme dipper pattern had worse prognosis either dead (41%) (25%) or had severe degree of disability (25%) (37%), respectively [11].
Core body temperature
4 studies [33,35,37] reported that increased temperature was associated to higher mortality rate except in one study which concluded an increased mortality rate above 39 °C and below 37 °C [35]. One study observed that post-stroke temperature elevation is associated to NIHSS, intubation, signs of infection at the time of admission and has a less favourable outcome [12]. One study reported higher peak body temperature on the first three days after stroke onset to be associated with increased infarct size and poor outcome. It was reported that every additional 1°C mean peak body temperature on day 2 and 3 was associated with an increased risk of poor outcome [33]. SAH patient with a temperature of f 37.94 ± .39°C showed a worse outcome than the SAH patients with a lower temperature. It was also observed that patients with delayed cerebral ischemia (DCI) had a significant higher body temperature (38.10 ± .18°C) [37]. However, one study reported an inverse correlation between neurological improvement and body temperature, indicating that higher body temperature was beneficial for stroke recovery in acute phase [31]. When body temperature was measured in hemiplegic stroke patients, it was observed that stroke patients had a lower temperature in the affected side [30]. Shereen et al, 2019 [11] has reported using CBT as one of the biomarkers for assessing the rhythm, but no reports were found about the results. Findings on clinical impacts have been summarised in
19
Treatment approaches to the disrupted circadian rhythm in stroke patients
4 studies explored the beneficial use of temperature targeted management (TTM), melatonin and light therapy in improving the clinical outcome after stroke [3,36,40,42]. Out of the 4 studies used, 2 were animal studies [36,42].
In a study conducted in mice induced with middle cerebral artery occlusion, it was observed that +33°C and +36°C temperature targeted management had significantly reduced the infarct size and improved the neurological outcome [36]. It was reported that prophylactic use of melatonin(10mg/kg) in mouse model for 7 consecutive days was significantly effective in decreasing the severity of stroke and enhanced the post-stroke outcome [42]. 30 mg melatonin administered through nasogastric tube showed significant improvement of GCS by day 5, mortality rate of 15% as against 30% in patients who did not take melatonin and decreased length of stay in hospital [40]. Study utilising naturalistic light in patients with low melatonin and abnormal diurnal pattern reported an increase in melatonin level with a reappearance of rhythm, although it was an abnormal rhythm in the end of 2 weeks along with a decrease in cortisol level. The group under naturalistic light had higher melatonin levels at the time of discharge compared to inclusion with an evolved rhythmicity (p = 0.007) [3]. Findings are summarised in Table 5.
Table 5. Treatment approaches to disrupted circadian rhythm in stroke patients Author, year,
reference
Study type, outcome variable
Sample size
Method used Findings
Lee et al.,2018[36] Animal study, TTM (32°C to 36°C) neuroprotective effect in MCAO induced in mice
n/a TTM MCAO+33°CTTM, MCAO+36°CTTM
both showed reduced infarct size and thus provides neuroprotectivity.
Feng et al.,2017 [42]
Animal study, pre-ischemic melatonin administration in MCAO mouse model n/a Intraperitoneal administration of 10mg/kg melatonin for 7 days
1.prophylactic melatonin administration reduced ischemic injury significantly. 2. increased survival rate 2 weeks post ischemia. Mojtahedzadeh et al., 2017 [40] Cross-sectional, /case-control 30mg melatonin in HS patients in ICU 40 20/mela tonin 20 w/o melaton in 30 mg melatonin every night
1.GCS score significantly improved in the melatonin group during the study. 2.Duration of mechanical ventilation and length of ICU stay shorter in the group who received melatonin. (Melatonin- avg 4 days, control- 12 days)
3.Mortality rate in Control was 30% as against 15% in study group.
20 Anders et al.,2019 [3] Quasi-randomised controlled trial, serum melatonin and cortisol in SP in naturalistic light (IU) and in indoor lighting (CU) 43; IU=23, CU=19
Naturalistic light 1. absence of normal diurnal pattern of melatonin at the time of inclusion (IU and CU)
2. Patients stimulated with naturalistic light showed an increased level of Melatonin as against the patients under standard indoor lighting after 2 weeks. 3.naturalisitc light helped to evolve an abnormal diurnal rhythm to melatonin secretion.
4. Cortisol level reduced in CU group at the time of discharge.
TTM-targeted temperature management, MCAO- Middle cerebral artery occlusion, IU-naturalistic light, CU- indoor light, HS- haemorrhagic stroke, ICU- intensive care unit, GCS- Glasgow Coma Scale,
Methodological aspects of the investigated biomarkers of diurnal rhythm
Time from stroke to biomarker assessment ranged from 3 hours to 3 months. All the studies using cortisol and melatonin assessed serum samples [3,4,11,14,22,28,29]. One study divided 24 h into 4 quartiles and measured the biomarkers from each quartile[11].One of the studies measured serum melatonin every and cortisol every 2 hours [14]; another study measured nocturnal melatonin only at one point [22]; one study measured cortisol at 2 points- 08:00 am and 16:00 pm [29].
Rectal, tympanic temperature was measured in [12,31,33], axillary temperature in [30,37], cutaneous temperature of hand and feet [30], and rectal temperature in [12] in the studies using cutaneous thermometers and infrared thermography. One of the studies measured temperature for 11 days starting from day 4 after stroke [37]. 3 measurements were taken per day by dividing each day into 8-hour periods (24:00-08:00, 08:00-16:00, 16:00-24:00) and the highest body temperature in each period was used in the analysis, giving data at 33 time points for each patient.[37]. Temperature was recorded once per day starting from 6 hours post stroke up to 3 days in another study [33]. One study using axillary temperature measured temperature from left and right axilla in hemiplegic patients and compared with the healthy group [30]. No studies reported a diurnal measurement of temperature.
Actigraphy reading was taken over 7 consecutive days in one study [23] while the other measured intradaily variability (IV) between 1 and 60 mins [39].
21
Table 2. changes in serum cortisol and melatonin and it’s clinical impacts
Author, year and reference Study design, outcome variable Sample size
Biomarker assessed Result/Conclusion
Shereen et
al.,2019[11]
Cross-sectional, PF, CBFV, EtCO2
and serum cortisol in SP vs control. Serum cortisol follow up in 3 months IS=60, HS=38, Control98 1.Serum cortisol 2. BP 3.CBT
1.Increased serum cortisol levels +loss of circadian rhythmicity in cortisol secretion vs controls- IS 24.6 ± 10.2, HS 23.7 ± 10.4, Control- 10.3 ± 5.2 (1st quartile; similar obs. In 2nd quartile).
2. plasma cortisol returned to normal values with the reappearance of the normal circadian rhythm in 3 months.
3.Loss of diurnal variation in BP (no nocturnal
dipping in 59 patients vs control). Barugh et al.,
2014 [9]
Review 48 articles Serum cortisol 1.high cortisol level in the first 7 days after stroke.
2. elevated cortisol related to poor prognosis.
Klimenko et al.,2015[26] Case control, serum cortisol TIA vs control 40; 20 TIA,20 control
Serum cortisol TIA patients had significantly higher level of cortisol. Zhang et al.,2016[29] Case control, serum cortisol with PSD and Non-PSD vs control,3 weeks after stroke PSD 34, Non-PSD 66, Control 50
Serum cortisol 1.Both PSD and non-PSD groups had elevated morning cortisol compared to the controls. (P<0.05; PSD- 508.86±119.51 nmol/L; non-PSD-420.83±70.04 nmol/L; control: 340.40±76.30 nmol/L).
2. Higher afternoon cortisol and absent cortisol circadian rhythm in PSD group.
Agarwal et al 2020[28] Cross-sectional, association of serum cortisol in SP to mortality, <6hrs
64 Serum cortisol 1.Elevated level of serum cortisol in SPs 2. High cortisol predicts poor prognosis.
22 Ratajczak et al..2017[14] Cross sectional, case control, cortisol and melatonin in acute IS vs controls, <2 d PS 18; 8 ISP 10control 1.serum cortisol 2.serum melatonin
1.Cortisol level in IS much higher than
reference range-195.47ng/ml vs. <50ng/ml at 4 pm and 341.15ng/ml vs. 150-250ng/ml at 8 am. Cortisol mesor was increased with advanced rhythm.
2.Melatonin mesor+ amplitude decreased after IS; Mesor– AIS- 18.2±8.5 pg/ml, Control-47.8±4.1ng/ml and Amp- AIS-16.7±6.3pg/ml, Control-42.2±3.7pg/ml. Lorente et al., 2018 [4] Cross-sectional Serum melatonin in MMCAI over 30 days
64 Serum melatonin 1.higher levels of melatonin were seen in patients who died from MMCAI than the patients who survived. (p<0.001)
2. Serum melatonin can predict 30 days mortality. Higher mortality in 30 days was seen in patients with increased melatonin levels. Zhang et al.,2017 [22] Case control, melatonin in IS with insomnia vs controls 25 IS;25 control Serum melatonin, MEQ
1.Decreased nocturnal melatonin in IS/ Insomnia vs controls.
2.Nocutrnal melatonin influence circadian rhythm, quality and pattern of sleep.
3. melatonin is positively correlated to NIHSS Mustafa et al.,2018 [10] Animal study, IS at 4 different Zeitgeber time points/6h intervals and its implication to tissue injury, circadian proteins.
70 mice Per1, Per2, Bmal1, Clock gene
1.Levels of PER1, Clock and Bmal1 were significantly increased in Mid-dark group ZT18 relative to ZT0 (ZT0 is lights on –06:00; ZT18-24:00)
2.ZT18 showed decreased tissue injury, oedema formation and a better neurological deficit score vs ZT0
Schaller N.
et al.,2014
[13]
Review n/a Clock gene 1.stroke occurrence shows a bimodal circadian pattern
2.disruption of clock gene increases susceptibility to stroke
3. different times of the day have different susceptibility to stroke depending on the expression level of the clock gene at that given point of time. Kantermann et al.,2014[24] Cross sectional, association b/w chronotype (mid-sleep on work-free days corrected for sleep deficit on workdays; MSFsc)
35 MCTQ 1.Chronotype (MSFsc) changed significantly
after stroke.
2. Changes in MSFsc varied with the internal
23
MEQ-Morning evening questionnaire, MCTQ- Munich chronotype questionnaire, MSFsc -mid-sleep on work-free days corrected for sleep deficit on workdays, PF-plasma fibrinogen, BP-blood pressure, CBFV-cerebral blood flow velocity, PSD- Post stroke depression, TIA- transient Ischaemic attack, IS- ischaemic stroke, HS- haemorrhagic stroke, SP-stroke patients, PS- post stroke, AIS- acute ischaemic stroke, CU-indoor lighting, IU- naturalistic lighting, MMCAI- Middle cerebral artery infarction, NIHSS- national Institutes of Health Stroke Scale, ICU- intensive care unit, GCS- Glasgow coma scale ,ZT-Zeitgeber time, ISP- Ischemic stroke patient ETCO2-endd-tidal CO2
Table 3. Changes in core body temperature and its clinical impacts. Author, year, reference Study design, outcome variable Sample size Temperature measurement Conclusion Ruborg et al.,2017[12] Cross sectional, <48hr PS Rectal &tympanic temp 400, IS=351, HS=49 1.Rectal temperature 2.Tympanic temperature
1. Temperature elevated within the first 48h of stroke.
2. NIHSS score, rectal (not tympanic) temp, intubation, CRP>50/infection symptoms, swallowing test (indicating dysphagia) are positively correlated to PBT within 48h. Alfieri et al.,2017[30] Cross-sectional, body temperature in hemiplegic SP vs controls 100 SP, 30 control 1.Axillary temp using cutaneous thermometer 2. cutaneous temp of hand and feet by
Stroke patients present lower temperature in the paretic side, especially the feet.
infrared thermography Khanevski et al.,2017[31] Cross-sectional, Body temp in <3h SP to NIHSS score 315 1.Temporal artery thermometer 2. Infrared tympanic device
inverse association between admission body temperature and neurological improvement in the early phase after admission. Geurts et al.,2016[33] Cross-sectional, body temperature association to infarct size and outcome on the day of admission to day three. 419 1.tympanic temperature 2.Rectal temperature
1. Body temperature were higher on day one, two, three than the day of admission. 2.Higher body temperature on first 3 days were associated to larger infarct size and poor functional outcome.
and internal time of stroke in IS.
24 Saxena et al.,
2015[35]
Cohort study, peak body temperature in TBI/Stroke patients' relation to mortality, <24h PS
83717 Not mentioned 1.TBI/stroke patients have an increased risk of mortality if the temperature is above 39 °C and below 37 °C.
Suehiro et
al.,2016[37]
Cross-sectional study, body temperature in SAH patients from day 4 to 14 and relation to clinical outcome and mortality 62 Axillary temperature
1. The mean body temperature in all patients was 37.41 ± .50°C. With a peak on day 5 and reaching its lowest on day 14. 2. Patients with a mean body temperature of 37.94 ± .39°C had a poor outcome compared to f 37.27 ± .43°C
3. Patients who developed DCI had a temperature of 38.10 ± .18°C as against 38.10 ± .18°C with no DCI which was consistent from day 4 to 14.
SAH-subarachnoid haemorrhage, DCI- delayed cerebral ischemia, CRP- C-reactive protein, SP- stroke patient, TBI- Traumatic brain Injury, NIHSS- national Institutes of Health Stroke Scale, HS-Haemorrhagic stroke, IS-Ischemic stroke PBT-post body temperature, PS-post stroke
Table 4. Changes in circadian rhythm using actigraphy Author, Year,
Reference
Study design, outcome variable
Sample size
Method used Conclusion
Zuurbier et
al.,2014[23]
Cohort study, 24-hour circadian rhythm assessed for fragmentation and instability by actigraphy in WML, LI, cerebral microbleeds 970, 43 LI Actiwatch for 7 consecutive days and nights
1.WML and microbleeds are significantly related to 24hour fragmented circadian rhythm.
2. No association found between LI and 24hr rhythm fragmentation parameters.
Gonçalves et
al.,2014[39]
To assess rest-activity rhythm by IV and IS using actimetry in a series of known time interval in Stroke, Parkinson’s and animal model 126; 52- SPs, 24 control Actiwatch IV between 1 and 60 mins IS in every 60 mins.
1.In stroke patients IVm (mean IV) was higher than the control group.
2.IV in all the intervals were higher for the stroke patients.
3.no significant difference between 2 groups when using IV 60.
WML- white matter lesions, LI- lacunar infarct, IV- intradaily variability, IS- interdaily stability, SP-Stroke patient.
25
DISCUSSION
This scoping review provides new insight into investigating the disruptions in diurnal rhythm in stroke patients. The findings from the review done on studies from 2014 to 2020 February shows significant changes in the diurnal rhythm in acute phase of stroke.
The data from articles on circadian pattern in stroke occurrence is consistent with previous findings that stroke exhibits a temporal pattern in occurrence with the highest peak in the late morning hours, between 06:00 am and 12:00 am and lowest in the evening hours. This variability may be associated with the circadian pattern of body temperature, physical activity, blood pressure, plasma cortisol, melatonin and platelet aggregation [16-20]. These may suggest that knowledge about diurnal rhythm disruptions may elucidate this temporal pattern seen in stroke onset, thus help for a better timing of diagnosis in high risk groups.
Changes in biomarkers of diurnal rhythm in stroke patients
The exact role of circadian disruption in stroke remains unknown. One of the possible mechanisms could be that cerebral hypoperfusion decreases blood and glucose to SCN; affecting the circadian entrainment property of the SCN, but there is not enough evidence to support this hypothesis. The pathophysiology of excessive cortisol secretion in acute phase of stroke could be related to reduced feedback inhibition of HPA axis, increased response to ACTH or proinflammatory cytokine release [28,29]. Melatonin secretion from the pineal gland is primarily under the control of SCN, but there are some other regions such as paraventricular nucleus of hypothalamus (PVS) and intermediolateral nucleus of the spinal cord (IML) involved [47]. From the review, elevated melatonin seen in strokes such as anterior circulation strokes outside the hypothalamic regions might be suggestive of regions other than the retinopineal neuronal having an important role in melatonin secretion [14].
Several explanations have been hypothesized for the initial temperature elevation. One of the possible explanations is that it’s partly due to the changes in local cerebral thermoregulatory centre in brain [43]. It may be suggested that the circadian disruption might be originating in SCN and changes in melatonin can have an impact on thermoregulatory centre.
The decreased night-time blood pressure could be due to the changes in autonomic nervous system functioning and changes in cortisol and epinephrine secretions in the acute stage of stroke [11]. It could be suggested that nocturnal fall in blood pressure may be associated with increased risk of stroke due to cerebral hypoperfusion.
Clinical impacts of circadian disruption in stroke patients
The review has revealed high cortisol is related to depression, delirium, and poor functional outcome. The changes in levels of melatonin can be a cause of insomnia after stroke. The analysis suggests that melatonin has an influence on various factors related to insomnia such as quality and pattern of sleep, severity of insomnia and fatigue levels in patients [22]. The sleep pathologies reported to last in stroke patients even after the acute phase (>3 months) may be because the insult to the circadian rhythm are more chronic rather than a transient change [22].
26
Similarly, our findings may suggest that reduction in core body temperature in the first three days after stroke can increase functional outcome and reduce infarct size [33, 36,37].
Treatment approaches to the disrupted circadian rhythm in stroke patients
In addition to its circadian rhythmicity function, melatonin has been studied for its strong neuroprotective roles. Melatonin has potent antioxidant and anti-apoptic functions [41,44]. Administration of exogenous melatonin has yielded promising results in animal studies. The findings from this review also supports the beneficial effects of administration of melatonin [42].
Light is thought to be one of the strongest exogenous factors that has an influence on the diurnal rhythmicity. Naturalistic light is an artificial light with specific wavelength that can emulate sunlight spectrum. The analysis from this review speculates interventional use of light in treatment strategies for stroke patients.
There has been conflicting information on the use of therapeutic hypothermia for neuroprotection and improving clinical outcome. One of the analysis suggests that higher temperature is favourable for clot lysis [31]. It is indicated that there might be a time dependent association between post-stroke body temperature and outcome.
Small trials and certain animal studies have shown the effectiveness of TTM, but in order to use it in clinical practice, large randomised trials should be undertaken.
Limitations of the methodological aspects and future prospective
This review suggests that serum cortisol, serum melatonin, CBT, clock gene expression and actigraphy can be used as reliable biomarkers for studying diurnal rhythm changes in stroke patients. However, there were several limitations to the methods adapted for analysing the biomarkers. In the studies using melatonin and cortisol, all the examined samples were serum samples, thus the difference in sensitivity in serum, urine and salivary samples could not be assessed. One of the studies reported that the higher concentrations in serum samples allow more resolution and therefore greater sensitivity [14]. Most of the studies used only one biomarker, of which were measured in insufficient time intervals.
Although studies revealed changes in temperature levels, none of the studies reported a diurnal measurement of temperature in stroke patients. Cutaneous thermometer and infrared thermography can detect temperature changes in a single timepoint; however, they lack practicality in assessing dynamic changes in the CBT rhythm over a prolonged time. Similarly, when temperature is measured from tympanic membrane or axilla, it must be measured on both sides. The use of telemetry system, ibuttons can serve as a possible solution to this as they have been reported to be a reliable method of cyclic and continuous temperature measurement [8]. The findings from this study suggests that a new method with using IV calculation over hourly sampling rate is more sensitive than the classic 60-minute sampling in detecting rhythm fragmentation using actigraphy.
Therefore, although melatonin, cortisol and CBT remain to be the gold standard for studying circadian variations in stroke patients, current methods adapted requires sampling procedures under strict well controlled laboratory conditions. Currently these biomarkers are measured only in single timepoints and hence the dynamic picture of circadian rhythm cannot be detected precisely. Moreover, it requires ample patient engagement, is expensive and needs huge workforce investment. Some studies have suggested assessing circadian rhythms using clock
27
genes from buccal cells, fibroblasts, adipose tissue etc. [15,34,40]. They are relatively non-invasive and allows an in-vitro assessment [40].
These studies are so far successful in animal models but is still a very novel emerging field and requires large clinical trials.
Findings from the current studies are very scarce and application in clinical practice is thus limited. It is in need to study further about the exact role of these disruptions as it could help to predict the onset of stroke, determine the multiple facets of stroke outcome, and enhance the treatment strategy focusing on re-setting the disruption. This could also become vital in diminishing many consequences associated with stroke such as insomnia, depression, cognitive decline, dementia and improve overall quality of life. New methodologies to measure the endogenous biomarkers more efficiently over a prolonged time should be studied. Researches targeting to normalize the rhythm disruptions might provide novel therapeutic interventions. A novel biomarker-based methodology and treatment should be the target of future studies.
28
CONCLUSION
This scoping literature review revealed that stroke causes the disruption of diurnal rhythm. There are significant changes in the level of endogenous circadian biomarkers; the acute phase of stroke was marked with significantly high levels of cortisol, low melatonin, and high core body temperature, changes in clock gene expression, rhythm fragmentations. Circadian disruptions are associated to severity of stroke, increased infarct size, poor functional outcome, increased mortality rate, insomnia and depression. Temperature target management and exogenous melatonin administration in animal studies showed beneficiary effects in re-establishing the diurnal rhythm and improving functional outcome. The interventional use of exogenous melatonin, temperature target management and light require more clinical trials to be used in clinical practice. Serum cortisol, melatonin, CBT, actigraphy can be used as reliable biomarkers for studying circadian rhythm changes in stroke. New methodological approaches aiming to assess the rhythm in a more cycle and dynamic manner so that the changes in the circadian rhythm can be detected more precisely are required.
Future Perspectives
Following are some of the areas highlighted for future researches:
1.Assess the diurnal changes in pre-stroke, stroke, and post-stroke settings.
2.Difference in changes in diurnal rhythm in mild, moderate and severe stroke and its clinical impact.
2.Studies measuring the biomarkers over a continuous longer period.
3.Stratify the biomarkers for their sensitivity and accuracy; use of actigraphy, clock gene assessment vs melatonin and cortisol.
4.Examine the association of diurnal changes with temporal pattern of stroke.
5.Assessbenefits of resetting the internal clock for better prognosis among stroke patients. 6. The role of exogenous melatonin, light therapy and TTM in re-establishing the diurnal rhythm among stroke patients and its efficacy in improving the functional outcome.
29
REFERENCES
1. Reinberg A, Ashkenazi I. Concepts in human biological rhythms. Dialogues in Clinical Neuroscience. 2003;5(4):327‐342.
2. Andreani T, Itoh T, Yildirim E, Hwangbo D, Allada R. Genetics of Circadian Rhythms. Sleep Medicine Clinics. 2015;10(4):413-421.
3.West A, Sennels H, Simonsen S, Schønsted M, Zielinski A, Hansen N et al. The Effects of Naturalistic Light on Diurnal Plasma Melatonin and Serum Cortisol Levels in Stroke Patients during Admission for Rehabilitation: A Randomized Controlled Trial. International Journal of Medical Sciences. 2019;16(1):125-134.
4. Lorente L, Martín M, Abreu-González P, Pérez-Cejas A, Ramos L, Argueso M et al. Serum melatonin levels are associated with mortality in patients with malignant middle cerebral artery infarction. Journal of International Medical Research. 2018;46(8):3268-3277.
5. Wu H, Wu C, Niu H, Wang K, Mo L, Shao A et al. Neuroprotective Mechanisms of Melatonin in Hemorrhagic Stroke. Cellular and Molecular Neurobiology. 2017;37(7):1173-1185.
6. Onaolapo A, Onaolapo O, Nathaniel T. Cerebrovascular Disease in the Young Adult: Examining Melatonin’s Possible Multiple Roles. Journal of Experimental Neuroscience. 2019;13:117906951982730.
7. Ramos E, Farré-Alins V, Egea J, López-Muñoz F, Reiter R, Romero A. Melatonin's efficacy in stroke patients; a matter of dose? A systematic review. Toxicology and Applied Pharmacology. 2020;392:114933.
8. 2. Słomko J, Zalewski P. The circadian rhythm of core body temperature (Part I): The use of modern telemetry systems to monitor core body temperature variability. Polish Hyperbaric Research. 2016;55(2).
9. Barugh A, Gray P, Shenkin S, MacLullich A, Mead G. Cortisol levels and the severity and outcomes of acute stroke: a systematic review. Journal of Neurology. 2014;261(3):533-545.
10. Beker M, Caglayan B, Yalcin E, Caglayan A, Turkseven S, Gurel B et al. Time-of-Day Dependent Neuronal Injury After Ischemic Stroke: Implication of Circadian Clock Transcriptional Factor Bmal1 and Survival Kinase AKT. Molecular Neurobiology. 2017;55(3):2565-2576.
11. Al-Ahwal S, Ragab O, Abo Elsafa A, Ghali A. Circadian and circannual patterns of stroke. The Egyptian Journal of Neurology, Psychiatry and Neurosurgery. 2019;55(1).
12.Ruborg R, Gunnarsson K, Ström J. Predictors of post-stroke body temperature elevation. BMC Neurology. 2017;17(1).
30
13. 1. Robert LeBlanc N. Circadian Rhythm in Stroke – The Influence of Our Internal Cellular Clock on Cerebrovascular Events. Journal of Clinical & Experimental Pathology. 2014;04(02). 14.Adamczak-Ratajczak A, Kupsz J, Owecki M, Zielonka D, Sowinska A, Checinska-Maciejewska Z, Krauss H, Michalak S, Gibas-Dorna M. Circadian rhythms of melatonin and cortisol in manifest Huntington's disease and in acute cortical ischemic stroke. Journal of physiology and pharmacology. 2017;68(4):539-546.
15. Nagoshi E, Saini C, Bauer C, Laroche T, Naef F, Schibler U. Circadian Gene Expression in Individual Fibroblasts. Cell. 2004;119(5):693-705.
16. M. S. Uddin, M. I. Hoque, M. K. Uddin, S. A. Kamol, R. H. Chowdhury. Circadian Rhythm of onset stroke in 50 cases of ischemic stroke. Mymensingh Medical Journal. 2015;24(1):121-126.
17. Koo Y, Yu S, Cho K, Jung K. Circadian Variation of Stroke Onset and Other Clinical Characteristics: A Single-Center Study. Journal of Korean Sleep Research Society. 2014;11(2):61-65.
18.Fodor D, Babiciu I, Perju-Dumbrava L. Circadian variation of stroke: a hospital based study. Medicine and Pharmacy Reports. 2014;87(4):242-249.
19.Choi Y, Seo I, Kim D, Oh H, Jeong D, Park H et al. Same Pattern of Circadian Variation According to the Season in the Timing of Ischemic Stroke Onset: Preliminary Report. Sleep Medicine Research. 2015;6(2):72-76.
20.Kabir M, Hasan A, Hasan M, Chakraborty S, Rahman M. Circadian variation in stroke: a hospital-based study. International Journal of Advances in Medicine. 2019;6(4):1236.
21. Fekadu G, Wakassa H, Tekle F. Stroke Event Factors among Adult Patients Admitted to Stroke Unit of Jimma University Medical Center: Prospective Observational Study. Stroke Research and Treatment. 2019;2019:1-8.
22. Zhang T, Zhang W, Li F. Relationship of nocturnal concentrations of melatonin, gamma-aminobutyric acid and total antioxidants in peripheral blood with insomnia after stroke: study protocol for a prospective non-randomized controlled trial. Neural Regeneration Research. 2017;12(8):1299.
23. Zuurbier L, Ikram M, Luik A, Hofman A, Van Someren E, Vernooij M et al. Cerebral small vessel disease is related to disturbed 24-h activity rhythms: a population-based study. European Journal of Neurology. 2015;22(11):1482-1487.
24. Kantermann T, Meisel A, Fitzthum K, Penzel T, Fietze I, Ulm L. Changes in Chronotype after Stroke: A Pilot Study. Frontiers in Neurology. 2015;5.
31
25. Raj K, Bhatia R, Prasad K, Padma Srivastava M, Vishnubhatla S, Singh M. Seasonal Differences and Circadian Variation in Stroke Occurrence and Stroke Subtypes. Journal of Stroke and Cerebrovascular Diseases. 2015;24(1):10-16.
26. Klimenko L, Skalny A, Turna A, Tinkov A, Budanova M, Baskakov I et al. Serum Trace Element Profiles, Prolactin, and Cortisol in Transient Ischemic Attack Patients. Biological Trace Element Research. 2015;172(1):93-100.
27. Rahman S, St. Hilaire M, Chang A, Santhi N, Duffy J, Kronauer R et al. Circadian phase resetting by a single short-duration light exposure. JCI Insight. 2017;2(7).
28.Agarwal A, Iqbaal H. SERUM-CORTISOL LEVELS IN SEVERITY OF STROKE. International Journal of Medical and Biomedical Studies. 2020;4(2).
29. Zhang X, Zou W, Yang Y. Effects of IL-6 and cortisol fluctuations in post-stroke depression. Journal of Huazhong University of Science and Technology [Medical Sciences]. 2016;36(5):732-735.
30. Alfieri F, Massaro A, Filippo T, Portes L, Battistella L. Evaluation of body temperature in individuals with stroke. NeuroRehabilitation. 2017;40(1):119-128.
31.Khanevski A, Naess H, Thomassen L, Waje-Andreassen U, Nacu A, Kvistad C. Elevated body temperature in ischemic stroke associated with neurological improvement. Acta Neurologica Scandinavica. 2017;136(5):414-418.
32. Alavoodin, Zakia, Rekha.S,. M, Sudha, C Ilamparithi, Kavimani, S, Balu.V. Genetic Basis of Circadian Rhythm - Concepts of Chronopharmacology and Chronotherapeutics. Indian Journal of Clinical Practice. 2009;20:109-114.
33. Geurts M, Scheijmans F, van Seeters T, Biessels G, Kappelle L, Velthuis B et al. Temporal profile of body temperature in acute ischemic stroke: relation to infarct size and outcome. BMC Neurology. 2016;16(1).
34. 1. Pagani L, Semenova E, Moriggi E, Revell V, Hack L, Lockley S et al. The Physiological Period Length of the Human Circadian Clock In Vivo Is Directly Proportional to Period in Human Fibroblasts. PLoS ONE. 2010;5(10):e13376.
35. Saxena M, Young P, Pilcher D, Bailey M, Harrison D, Bellomo R et al. Early temperature and mortality in critically ill patients with acute neurological diseases: trauma and stroke differ from infection. Intensive Care Medicine. 2015;41(5):823-832.
36.Lee J, Lim J, Chung Y, Chung S, Park I, Kim C et al. Targeted Temperature Management at 33°C or 36°C Produces Equivalent Neuroprotective Effects in the Middle Cerebral Artery
32
Occlusion Rat Model of Ischemic Stroke. SHOCK. 2018;50(6):714-719.
37. Suehiro E, Sadahiro H, Goto H, Oku T, Oka F, Fujiyama Y et al. Importance of Early Postoperative Body Temperature Management for Treatment of Subarachnoid Hemorrhage. Journal of Stroke and Cerebrovascular Diseases. 2016;25(6):1482-1488.
38. Zuurbier L, Luik A, Hofman A, Franco O, Van Someren E, Tiemeier H. Fragmentation and Stability of Circadian Activity Rhythms Predict Mortality. American Journal of Epidemiology. 2014;181(1):54-63.
39. Gonçalves B, Cavalcanti P, Tavares G, Campos T, Araujo J. Nonparametric methods in actigraphy: An update. Sleep Science. 2014;7(3):158-164.
40.Saini C, Brown S, Dibner C. Human Peripheral Clocks: Applications for Studying Circadian Phenotypes in Physiology and Pathophysiology. Frontiers in Neurology. 2015;6.
41. Kleszczyński K, Zillikens D, Fischer T. Melatonin enhances mitochondrial ATP synthesis, reduces reactive oxygen species formation, and mediates translocation of the nuclear erythroid 2-related factor 2 resulting in activation of phase-2 antioxidant enzymes (γ-GCS, HO-1, NQO1) in ultraviolet rad. Journal of Pineal Research. 2016;61(2):187-197.
42.Feng D, Wang B, Wang L, Abraham N, Tao K, Huang L et al. Pre-ischemia melatonin treatment alleviated acute neuronal injury after ischemic stroke by inhibiting endoplasmic reticulum stress-dependent autophagy via PERK and IRE1 signalings. Journal of Pineal Research. 2017;62(3):e12395.
43.Sung C, Lee T, Chu N. Central Hyperthermia in Acute Stroke. European Neurology. 2009;62(2):86-92.
44. Onaolapo A, Onaolapo O, Nathaniel T. Cerebrovascular Disease in the Young Adult: Examining Melatonin’s Possible Multiple Roles. Journal of Experimental Neuroscience. 2019;13:117906951982730.
45. Gottlieb E, Landau E, Baxter H, Werden E, Howard M, Brodtmann A. The bidirectional impact of sleep and circadian rhythm dysfunction in human ischaemic stroke: A systematic review. Sleep Medicine Reviews. 2019;45:54-69.
46.Kumar Jha P, Challet E, Kalsbeek A. Circadian rhythms in glucose and lipid metabolism in nocturnal and diurnal mammals. Molecular and Cellular Endocrinology. 2015;418:74-88. 47. Borjigin J, Li X, Snyder S. THE PINEAL GLAND AND MELATONIN: Molecular and Pharmacologic Regulation. Annual Review of Pharmacology and Toxicology. 1999;39(1):53-65.
33
48. Hickie I, Naismith S, Robillard R, Scott E, Hermens D. Manipulating the sleep-wake cycle and circadian rhythms to improve clinical management of major depression. BMC Medicine. 2013;11(1).
49. Refinetti R. The circadian rhythm of body temperature. Frontiers in Bioscience. 2010;15(1).
