Lunar rhythmicity in the actigraphic sleep patterns of older adults with chronic pain and sleep disturbances is associated with the severity of their self-reported sleep disturbance

The sleep–wake cycle represents the most prominent 24-h physiological and behavioral rhythm in most animals. Humans are day-active, and before they had widespread access to electricity, dusk signaled the imminent end of daily activity. One notable exception to this otherwise inescapable diurnality was evening activity during moonlit nights. A recent study of rural communities showed that during the nights immediately before the full moon, sleep onset is delayed, and sleep duration is shortened. Surprisingly, a similar effect on sleep timing was also observed in young adults living in Seattle, WA, who have widespread access to electric light [1]. These results are consistent with previous reports on different age ranges, using both sleep diaries and polysomnographic recordings [2, 3]. However, most of the evidence of lunar modulation of sleep comes from young and middle-aged healthy adults. This raises the question of whether lunar regulation of sleep is present and similar in other developmental stages, such as older adults, and in different disease states.