Does sleep protect against ischemic stroke?: less frequent ischemic strokes but more severe ones

Stroke occurrence follows a circadian curve, with a higher frequency in the morning. This curve changes if the hours of sleep also change. Our aim was to evaluate the characteristics, risk factors, and prognosis associated with sleep stroke. Patients with ischemic stroke (n = 813), consecutively assessed in our hospital for 2 years, were recorded with the time of clinical onset, pathological antecedents, severity (NIHSS), clinical classification, etiologic TOAST classification, and functional outcome at 3 months (modified Rankin scale). When clinical disturbance appeared during night sleep time it was considered as sleep stroke (SS). The rest were considered wakefulness stroke (WS). Differences SS-WS were analyzed with chi(2), t-student, Mann-Whitney U, and logistic regression tests. From 813 patients included, 127 were SS (15.6%). The SS frequency was less than expected for the corresponding interval of hours. After the univariate analysis and posterior logistic regression, obesity was a factor associated with SS. Adjustment for age and gender revealed that atrial fibrillation (AF) was less frequent in the SS group. There were no differences for other risk factors or in the etiologic distribution. SS had a greater initial clinical severity and a worse functional outcome at 3 months. This functional outcome was dependent on the initial clinical severity. Whilst sleep could be associated with a lesser stroke occurrence, it could also be associated with a higher severity. Obesity appears as a factor related to SS whilst AF appears related to WS.