Changes in chronotype after stroke: a pilot study

I have absolutely no idea what possible use this could be for survivors and their rehab, so punt it to your doctor.
http://journal.frontiersin.org/article/10.3389/fneur.2014.00287/full?
Thomas Kantermann^1,2*, Andreas Meisel^3,4, Katharina Fitzthum^3,4, Thomas Penzel⁵, Ingo Fietze⁵ and Lena Ulm^3,4,6

• ¹Chronobiology Unit, Groningen Institute for Evolutionary Life Sciences, University of Groningen, Groningen, The Netherlands
• ²Clinical Centre, Institute for Occupational, Social and Environmental Medicine, Ludwig-Maximilians University Munich, Munich, Germany
• ³NeuroCure Clinical Research Center, Charité – Universitätsmedizin Berlin, Berlin, Germany
• ⁴Department of Neurology, Center for Stroke Research Berlin, Charité – Universitätsmedizin Berlin, Berlin, Germany
• ⁵Center of Sleep Medicine, Charité – Universitätsmedizin Berlin, Berlin, Germany
• ⁶Centre for Clinical Research, The University of Queensland, Herston, QLD, Australia

This study aimed to elucidate associations between stroke onset and severity as well as chronotype (phase of entrainment) and internal time of stroke. Fifty-six first-ever ischemic stroke patients participated in a cross-sectional study assessing chronotype (mid-sleep on work-free days corrected for sleep deficit on workdays; MSF_sc) by applying the Munich ChronoType Questionnaire (MCTQ). The MCTQ was completed twice, on average 68 ± 24 (SD) days post stroke and retrospectively for the time before stroke. To assess the impact of stroke in relation to internal time, InT_stroke was calculated as MSF_sc minus local time of stroke. Stroke severity was assessed via the standard clinical National Institute Health Stroke Scale (NIHSS) and modified Ranking Scale (mRS), both at hospital admission and discharge. Overall, most strokes occurred between noon and midnight. There was no significant association between MSF_sc and stroke onset. MSF_sc changed significantly after stroke, especially in patients with more severe strokes. Changes in MSF_sc varied with InT_stroke – the earlier the internal time of a stroke relative to MSF_{sc-before-stroke}, the more MSF_sc advanced after stroke. In addition, we provide first evidence that MSF_sc changes varied between stroke locations. Larger trials are needed to confirm these findings.

Introduction

The onset of vascular events exhibits a circadian (about 24-h) pattern, with a prominent peak in the morning hours and a second, smaller peak in the early evening (1–4). This phenomenon is thought being caused by diurnal variations in underlying pathophysiological mechanisms, e.g., platelet aggregation, blood pressure, and catecholamine concentrations (3, 5). Several animal studies demonstrated that cerebrovascular events, in turn, also impact circadian rhythms and sleep architecture (6–9). Longer latencies to fall asleep, fragmented sleep, NREM sleep instability, and hypersomnia have also been described in stroke patients, indicating changes in sleep homeostasis and circadian rhythmicity after stroke (10, 11). Two studies with small sample sizes provided some evidence of altered timing in urinary melatonin as a marker of disturbed circadian rhythms in stroke patients (12, 13). However, knowledge on the interplay between sleep homeostasis, the circadian timing of sleep, and vascular events is still incomplete.

The circadian timing of sleep is regulated by an internal clock, which is synchronized (entrained) by light to the 24-h day (14, 15). The relation between external (local) and internal (circadian) time is called phase of entrainment (16) and people that differ in this trait are referred to as different chronotypes. Chronotype can easily be assessed with the Munich ChronoType Questionnaire [MCTQ; (16)] as the mid-point of sleep on work-free days (MSF), corrected for sleep deficit accumulated across the workweek (MSF sleep corrected; MSF_sc). MSF_sc as a measure for internal time allows calculating the internal time point of a physiological event (17, 18). Social jetlag (the difference between MSF and mid-sleep on workdays, MSW) is a surrogate measure for circadian rhythm disruption and has been linked to elevated heart rate in shift-workers (19), smoking (20), and depression (21). To date, no study has assessed phase of entrainment (chronotype) and social jetlag before and after stroke to compare the impact of stroke in relation to internal time.

The current study was the first to investigate associations between stroke onset and severity and internal time before and after stroke. We hypothesized that (a) there is a correlation between chronotype (MSF_sc) and stroke onset, (b) experiencing a stroke results in chronotype changes, and (c) the impact of stroke varies with the internal time point a stroke happened.