Age-related effects on circadian phase in the sleep of patients with depression and insomnia

We examined whether an age-related phase advance was present in 60 patients with depression and insomnia (mean age 41.5 [12.5] years) using diaries and 5 weekdays of actigraphy. Actigraphy was analyzed with functional data analysis. The low point of activity (bathyphase) for each subject was fitted by cosine function with 24-hr cycle time. Linear regression analysis revealed that increasing age was associated with earlier bedtimes (p < 0.001), shorter sleep latencies (p < 0.05), and earlier bathyphase (p < 0.001). These findings are consistent with prior reports of age-dependent phase-advances in sleep behavior in self-reported good sleepers and reinforce the premise that individualized behavioral therapy of older persons with insomnia may require prescription of earlier bedtimes and earlier rise times than would be employed in younger persons with insomnia. Further, we demonstrate that aging of the sleep system, at least as reflected in actigraphy, occurs as early as the third decade.