Actigraph measures of sleep disturbance are associated with higher daytime cortisol among older adults, according to a recent study. However, cross-sectional data cannot distinguish causal direction or whether cortisol and sleep disruption have a common cause. Salivary cortisol samples and actigraphy sleep data were collected from a random subsample of participants in the National Social Life, Health and Aging Project, a nationally-representative probability sample of adults aged 62-90 (n=672). Sleep characteristics were derived from wrist actigraphy (fragmentation, Wake After Sleep Onset [WASO], and duration) and from survey responses about usual sleep duration and sleep problems. Researchers found:

• From actigraphy, both higher fragmentation score and longer WASO were significantly associated with higher daytime cortisol; sleep duration was not.
• Self-reported sleep duration and sleep problems were also not associated with cortisol.