Sleep duration and health among older adults: associations vary by how sleep is measured

Cohort studies have found that short and long sleep are both associated with worse outcomes, compared with intermediate sleep times. While demonstrated biological mechanisms could explain health effects for short sleep, long-sleep risk is puzzling. Most studies reporting the U shape use a single question about sleep duration, a measurement method that does not correlate highly with objectively measured sleep. We hypothesised that the U shape, especially the poor outcomes for long sleepers, may be an artefact of how sleep is measured. We examined the cross-sectional prevalence of fair/poor health by sleep hour categories (≤6, ≤7, ≤8, ≤9, >9 h) in a national US sample of adults aged 62-90 that included several types of sleep measures (n=727). Survey measures were: a single question; usual bedtimes and waking times; and a 3-day sleep log. Actigraphy measures were the sleep interval and total sleep time. Fair/poor health was regressed on sleep hour categories adjusted for demographic...