Early sleep, longer time in bed tied to dementia risk in older adults

Older adults who sleep before 9 P.M. and have prolonged sleep duration appear to be at an increased risk of dementia, a recent study has found.

Researchers conducted a population-based cohort analysis of 1,982 participants aged ≥60 years who were free of dementia at baseline. Sleep parameters were measured both at baseline and at the follow-up around 4 years later. The Mini-Mental State Examination (MMSE) was used to measure cognitive function. Dementia and Alzheimer’s disease (AD) diagnoses were also included in the assessment.

The average follow-up period was 3.7 years, during which time 97 participants had been diagnosed with dementia and 68 with AD. Restricted cubic spline curves revealed a J-shaped interaction between dementia risk and time in bed, rise time, and sleep duration.

Categorizing sleep parameters into tertiles revealed that participants with baseline sleep length >8 hours were at a nearly 70-percent increased risk of dementia (hazard ratio [HR], 1.69, 95 percent confidence interval [CI], 1.01–2.83). Sleep duration 7–8 hours was used as a reference.

Similarly, those who went to bed before 9 P.M. (vs 10 P.M. or later) were more than twice as likely to develop dementia (HR, 2.17, 95 percent CI, 1.22–3.87). Early bedtime (HR, 2.25, 95 percent CI, 1.12–4.50) and mid-sleep time (earlier than 1 A.M.; HR, 2.51, 95 percent CI, 1.45–4.34) also significantly aggravated the risk of AD.

“Future intervention studies may help clarify whether moderately reducing time in bed and delaying sleep timing can slow down cognitive decline and delay dementia onset in older adults,” the researchers said.