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Wrist actigraphy has been used to assess sleep in older adult populations for nearly half a century. Over the years, the continuous raw activity data derived from actigraphy has been used for the characterization of factors beyond sleep/wake such as physical activity patterns and circadian rhythms. Behavioral activity rhythms (BAR) are useful to describe individual daily behavioral patterns beyond sleep and wake, which represent important and meaningful clinical outcomes. This paper reviews common rhythmometric approaches and summarizes the available data from the use of these different approaches in older adult populations. We further consider a new approach developed in our laboratory designed to provide graphical characterization of BAR for the observed behavioral phenomenon of activity patterns across time. We illustrate the application of this new approach using actigraphy data collected from a well-characterized sample of older adults (age 60+) with osteoarthritis (OA) pain and insomnia. Generalized additive models (GAM) were implemented to fit smoothed nonlinear curves to log-transformed aggregated actigraphy-derived activity measurements. This approach demonstrated an overall strong model fit (R2 = 0.82, SD = 0.09) and was able to provide meaningful outcome measures allowing for graphical and parameterized characterization of the observed activity patterns within this sample.

To date, studies of the natural history of insomnia have focused on the prevalence, incidence, and persistence of chronic insomnia. While these studies have provided seminal information about the epidemiology of insomnia, no studies to date, have been conducted in a manner to 1) allow for a close resolution of the “transitions” from good sleep to acute insomnia, from acute insomnia to the recovery of good sleep, or from acute insomnia to chronic insomnia and/or 2) allow for a comprehensive assessment of the factors that have been theorized to mediate or moderate these transitions.1–4 The present paper provides a review of these issues and sets forth a research agenda.