The Effect of Sleep Duration and Excessive Daytime Sleepiness on All-Cause Dementia: A Longitudinal Analysis from the Hunter Community Study.

OBJECTIVES

It has been proposed that abnormal sleep duration and excessive daytime sleepiness might be risk factors for dementia. This study assessed the interaction between sleep duration and excessive daytime sleepiness, and the effect of sleep duration in the presence or absence of excessive daytime sleepiness on dementia risk in community-dwelling older adults.

DESIGN

A longitudinal study.

SETTING AND PARTICIPANTS

Data from 2187 community-dwelling participants with mean age 70 years from the Hunter Community Study were included in this study.

METHODS

Participants were classified as participants with long sleep duration (slept >8 hours per night), recommended sleep duration (7-8 hours) as per the National Sleep Foundation, or short sleep duration (slept <7 hours per night). The Berlin Questionnaire was used to identify excessive daytime sleepiness. Dementia was defined as per International Classification of Diseases, 10 Revision codes. To calculate all-cause dementia risk, the Fine-Gray sub-distribution hazard model was computed with death as a competing risk.

RESULTS

Over a mean follow-up of 6 years, 64 participants developed dementia and 154 deaths were identified. The average onset of dementia was 5.4 years. Long sleep duration was associated with increased dementia risk only in the presence of excessive daytime sleepiness (adjusted hazard ratio, 2.86; 95% confidence interval 1.03-7.91). A statistically significant interaction was found between excessive daytime sleepiness and sleep duration for all-cause dementia.

CONCLUSIONS AND IMPLICATIONS

Long sleep duration with excessive daytime sleepiness was associated with increased risk of all-cause dementia. This suggests the importance of promoting awareness of healthy sleep and the possible role of nurturing good quantity and quality sleep in reducing the risk of dementia.