Daytime sleepiness is associated with 3-year incident dementia and cognitive decline in older Japanese-American men.

OBJECTIVES

To assess the longitudinal association between sleep disturbances (insomnia and daytime sleepiness) and incidence of dementia and cognitive decline in older men.

DESIGN

Community-based longitudinal cohort study.

SETTING

The Honolulu-Asia Aging Study of dementia that is linked to the Honolulu Heart Program's fourth examination, conducted 1991-1993, and the 3-year follow-up fifth examination, conducted 1994-1996.

PARTICIPANTS

Two thousand three hundred forty-six Japanese-American men age 71 to 93 years who screened negative for prevalent dementia at baseline and were screened again for dementia incidence in a 3-year follow-up examination.

MEASUREMENTS: Baseline self-reports of trouble falling asleep or early morning awakening (insomnia) and being sleepy during the day (daytime sleepiness); Cognitive Abilities Screening Instrument (CASI) scores from baseline and followup; clinical diagnosis of incident dementia; and other baseline measures including age, years of education, body mass index, depressive symptoms, and history of hypertension, heart disease, diabetes mellitus, asthma, and use of benzodiazepines.

RESULTS

After adjusting for age and other factors, persons reporting excessive daytime sleepiness at baseline (8%) were twice as likely to be diagnosed with incident dementia than were those not reporting daytime sleepiness (odds ratio (OR)=2.19, 95% confidence interval (CI)=1.37-3.50) and about 40% more likely to have >or=9 point drop in their CASI score between examinations (OR=1.44, 95% CI=1.01-2.08). In contrast, insomnia was not associated with cognitive decline or incidence of dementia.

CONCLUSIONS

Daytime sleepiness in older adults may be an early indicator of decline in cognitive functioning and onset of dementia.