Impact of Insufficient or Excessive Sleep Duration on Cognitive Function After Stroke: The Norwegian Cognitive Impairment After Stroke Study

Background The impact of sleep duration on cognition, particularly in the context of poststroke cognitive impairment, is not fully understood. Therefore, our objective was to investigate how sleep duration after stroke predicts poststroke cognitive impairment. Methods and Results Patients admitted with acute stroke between 2015 and 2017 were consecutively recruited to the Nor‐COAST (Norwegian Cognitive Impairment After Stroke) study and invited to follow‐up assessments at 3 and 18 months. Time in bed, used as a surrogate for sleep duration at 3 months post stroke, was measured using the activPAL thigh‐worn sensor over a 3‐day period. Sleep duration was categorized into 3 groups: <7 hours (insufficient), 7 to 9 hours (reference), and ≥9 hours (excessive). Cognitive impairment was assessed based on the Diagnostic and Statistical Manual of Mental Disorders (Fifth Edition) criteria at 3‐ and 18‐month follow‐up. Out of the 815 patients, we included 443 (54%) prestroke cognitive healthy with valid activPAL registration in this analysis. Mean±SD age was 71.2±11.4 years, 185 (42%) were women, 363 (82%) had prestroke modified Rankin Scale score <2, and 345 (78%) suffered a minor stroke (National Institutes of Health Stroke Scale score ≤5). On average, participants spent 8.3±1.4 hours in bed each night, 17.2% had a sleep duration <7 hours, and 25% slept more than 9 hours. Insufficient (odds ratio OR, 3.6 95% CI, 1.3–10.2, and OR, 1.4 95% CI, 0.5–3.8) and excessive (OR, 2.8 95% CI, 1.1–7.5, and OR, 3.3 95% CI, 1.3–8.1) sleep duration were associated with an increased risk of cognitive impairment at 3‐ and 18‐month follow‐up, respectively. Conclusions Insufficient or excessive sleep duration was associated with poststroke cognitive impairment.