Actigraphic sleep characteristics among older Americans

ObjectivesTo 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.DesignCross-sectional study.SettingSleep substudy within Wave 2 (2010-2011) of the ongoing National Social Life, Health, and Aging Project.ParticipantsSeven hundred and thirty-nine National Social Life, Health, and Aging Project participants aged 62-90 years.InterventionNot applicable.MeasurementsStudy participants wore a wrist actigraph for 72 hours, and sleep properties were compared across demographic, socioeconomic, and health-behavior–related lines.ResultsActigraph-estimated sleep time averaged 7.2 hours (SE, 0.06 hour) each night; the majority of the sample (80%) slept between 5.8 and 8.6 hours per night. Average time spent awake after sleep onset (WASO) was 39 minutes (SE, 1.2 minutes). Women had significantly more total sleep time and lower sleep fragmentation compared with 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 < .01) and greater sleep fragmentation (2.3 percentage points, P < .001). WASO was significantly higher and sleep percentage significantly lower among those with less education.ConclusionsBoth short sleepers and long sleepers—often conventionally defined as obtaining < 6 and > 9 hours per 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.