Actigraphic sleep characteristics among older Americans

Abstract

Objectives: To date, there has been no evidence about objectively measured sleep characteristics from a representative national probability sample of adults in the United States. We used actigraphy to measure the sleep characteristics of older Americans. Design: Cross-sectional study. Setting: Sleep sub-study within Wave 2 (2010-2011) of the ongoing National Social Life, Health and Aging Project (NSHAP). Participants: Seven hundred and thirty-nine NSHAP participants aged 62-90. Intervention: Not applicable. Measurements: Study participants wore a wrist actigraph for 72 hours and sleep properties were compared across demographic, socioeconomic, and health-behavior related lines. Results: Actigraph-estimated sleep time averaged 7.2 hours (SE 0.06 hr) each night; the majority of the sample (80%) slept between 5.8 and 8.6 hours/night. Average time spent awake after sleep onset (WASO) was 39 minutes (SE 1.2 min). Women had significantly more total sleep time and lower sleep fragmentation compared to men. Total sleep time increased significantly with age although sleep percentage decreased with age. Compared with White participants, African American participants had significantly more WASO (9.2 minutes, p < 0.01) and greater sleep fragmentation (2.3 percentage points, p < 0.001). WASO was significantly higher and sleep percentage significantly lower among those with less education. Conclusions: Both short sleepers and long sleepers - often conventionally defined as obtaining <6 and >9 hrs/night, respectively - are relatively rare among older Americans when sleep is estimated by actigraphy. Sleep quality is significantly poorer among men, African Americans, and those with less education.