Association of sleep duration with cognitive performance and structural brain differences: A large population‐based cross‐sectional study

Abstract

AbstractBackgroundSleep duration has been linked to dementia risk; however, its association with cognitive functioning in specific domains and the underlying mechanisms remain unclear. We aimed to examine the association of sleep duration with cognitive performance and structural brain differences using magnetic resonance imaging (MRI).MethodsWithin the UK Biobank, 43,255 dementia‐free participants (aged ≥44, 52.0% female) were included. Self‐reported sleep duration (hours/day) was recorded following a structured questionnaire and trichotomized as short (≤5), normal (6‐8), and long (≥9) sleep. Cognitive functioning (including fluid intelligence, pairs matching, reaction time, and numeric memory) was evaluated using a touchscreen test battery. MRI scans were performed, and total and regional brain volumes (including white matter, gray matter, and hippocampus), and white matter hyperintensities (WMH) were measured. Data on lifestyle factors and medical conditions were collected. Data were analyzed using linear regression.ResultsOf all participants, 2092 (4.8%) had short, 38,041 (87.9%) had normal, and 3122 (7.2%) had long sleep. In multi‐adjusted linear regression, compared with normal sleep duration, both short (β: ‐0.14, 95%, CI: ‐0.19 to ‐0.10) and long (β: ‐0.06, 95% CI: ‐0.10 to ‐0.03) sleep were related to poorer performance in fluid intelligence. Long sleep was also associated with poorer numeric memory (β: ‐0.06, 95% CI: ‐0.10 to ‐0.01). In MRI data analyses, compared with normal sleep duration, short sleep was related to a smaller hippocampus volume (β: ‐0.05, 95% CI: ‐0.09 to ‐0.01), while long sleep was associated with smaller total brain (β: ‐4.51, 95% CI: ‐6.82 to ‐2.21), gray matter (β: ‐3.32 95% CI: ‐4.70 to ‐1.94), and hippocampus (β: ‐0.06, 95% CI ‐0.09 to ‐0.02) volumes, but greater WMH (β: 0.05, 95% CI: 0.01 to 0.08), after adjusting for confounders.ConclusionsShort and long sleep durations are associated with poorer cognitive performance in different domains. Short sleep may indicate neurodegeneration, and long sleep may implicate both neurodegenerative and vascular changes in the brain.