MONDAY, Sept. 26, 2022 (HealthDay News) — Long time in bed (TIB) and early sleep timing are associated with an increased risk for dementia, according to a study published online Sept. 21 in the Journal of the American Geriatrics Society.

Rui Liu, M.D., from Shandong University in Jinan, China, and colleagues examined associations of sleep timing and TIB with dementia and cognitive decline in older adults. The analysis included 1,982 participants aged 60 years and older with a mean follow-up of 3.7 years.

The researchers found a J-shaped association of sleep duration, TIB, and rise time with dementia risk. There was a reverse J-shaped association with mid-sleep time. There was a higher risk for incident dementia for baseline sleep duration of more than eight hours versus seven to eight hours (adjusted hazard ratio [aHR], 1.69), for bedtime before 9 p.m. versus 10 p.m. or later (aHR, 2.17), and for mid-sleep time before 1 a.m. versus 1 to 1:30 a.m. (aHR, 2.00). There was a significant association seen between early bedtime and mid-sleep time with incident Alzheimer disease (HR range, 2.25 to 2.51). Baseline long TIB, early bedtime and mid-sleep time, early and late rise time, prolonged TIB, and advanced bedtime and mid-sleep time from baseline to follow-up were associated with a greater decline in the Mini-Mental State Examination score among individuals free of dementia at follow-up, particularly among men or participants who were aged 60 to 74 years.

“This suggests that cognitive function should be monitored in older adults who report prolonged time in bed and advanced sleep timing, especially in older individuals aged 60 to 74 years and men,” the authors write.

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