Sleep moderates the effects of exercise on cognition in chronic stroke: secondary analysis of a randomized trial

BackgroundExercise (EX) or cognitive and social enrichment (ENRICH) are two promising strategies for promoting cognitive function post-stroke. Sleep may moderate the effects of these interventions on cogntion, whereby intervention effects may be more robust among individuals suffering from poor sleep. We examined whether sleep moderates the effects of EX or ENRICH on cognitive function in adults with chronic stroke. MethodsSecondary analysis of a three-arm parallel, single-blinded, randomized clinical trial among community-dwelling adults aged 55+ years with chronic stroke (i.e., [≥]12 months since stroke). Participants were randomized to 2x/week EX, ENRICH, or balance and tone control (BAT). At baseline, device-measured sleep duration and efficiency were measured using MotionWatch8 wrist-worn actigraphy; self-reported quality was measured by Pittsburgh Sleep Quality Index (PSQI). Participants were categorized at baseline as having good or poor: 1) device-measured duration; 2) device-measured efficiency; or 3) self-reported quality. The primary cognitive outcome was Alzheimers Disease Assessment Scale Plus (ADAS-Cog-Plus) measured at baseline, 6 months (end of intervention), and 12 months (6-month follow-up). Linear mixed models examined if baseline sleep categorizations (i.e., good/poor) moderated the effects of EX or ENRICH on ADAS-Cog-Plus. ResultsWe enrolled 120 participants in the trial (EX=34; ENRICH=34; BAT=52). Baseline sleep categorization did not moderate the effect of ENRICH on ADAS-Cog-Plus; however, it moderated the effect of EX. EX participants with poor baseline sleep efficiency (estimated mean difference: -0.48; 95% CI:[-0.85, -0.10]; p=0.010) or self-reported sleep quality (estimated mean difference: -0.38; 95% CI:[-0.70, -0.07]; p=0.014) had significantly better ADAS-Cog-Plus performance at 6 months compared with BAT participants with poor sleep. There was no effect of EX on ADAS-Cog-Plus for participants with good baseline sleep. ConclusionThe effects of EX on cognitive function in adults with chronic stroke is moderated by sleep, whereby poor sleepers benefit more.