Dose-response associations of device measured sleep regularity and duration with incident dementia in 82391 UK adults

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ABSTRACT Objectives To evaluate the associations of device-measured sleep duration and regularity with incident dementia, and to explore whether regular sleep might mitigate any association of sleep duration with dementia. Methods This population-based prospective cohort study of 82391 adults from the UK Biobank accelerometry subsample included adults aged 43 to 79 years old in England, Scotland, and Wales. Sleep duration (h/day) and Sleep Regularity Index (SRI, range 0-100) were calculated from the wrist-worn accelerometry data collected by participants over the course of one week. Cox proportional hazard models were used to estimate the hazard ratios (HRs) and assess the independent associations between sleep and incident dementia after adjustment for common demographic and contextual covariates. Results Over a mean follow-up of 7.9 years, during which 694 incident dementia cases occurred, there was a U-shaped association between sleep duration and incident dementia. Short sleep (<7 h) was associated with increased dementia risk, while long sleep (≥ 8h) was not significantly associated with dementia risk. The median sleep duration for short sleepers (<7 h) of 6.5 hours was associated with an HR of 1.19 (95% CI 1.01, 1.40) for incident dementia. Sleep regularity was negatively associated with dementia risk in a near-linear fashion. The sample median SRI of approximately 73, compared to the reference point of 51, was associated with an HR of 0.76 (95%CI 0.61, 0.94). The SRI value where the risk reduction was 50% of the maximum observed of 66, was associated with an HR of 0.77 (95%CI 0.63, 0.95). Among individuals with sleep duration outside the optimal range (too short or too long), less regular sleep was associated with increased risk of dementia. Among those with optimal sleep duration (7-8h/day), there was no significant association between sleep regularity and dementia risk. Compared to the reference point (SRI: 51), an SRI value of 62 for non-optimal sleepers was associated with a 25% reduction in risk for dementia (HR: 0.75; 95% CI 0.63, 0.90). Conclusions A regular sleep pattern may mitigate some adverse effects of inadequate sleep duration, suggesting that interventions aimed at improving sleep regularity may be a suitable option for people not able to achieve the recommended hours of sleep.

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