Actigraphy utilizes a wristwatch-like portable device which contains an accelerometer, a clock, internal memory, and a photo sensor. It records the rest/activity cycle which may correspond to the sleep/wake cycle. It may assist to determine the sleep patterns in normal healthy adult population, to evaluate patients suspected of advanced sleep phase syndrome (ASPS), delayed sleep phase syndrome (DSPS), shift work sleep disorder, and other circadian sleep disorders including jet lag and non-24 h sleep/wake syndrome. It is used to determine the circadian rhythm patterns in patients with insomnia (including insomnia associated with depression) and hypersomnia.

When sleep diaries are used in conjunction with actigraphy, more information can be obtained in regard to sleep/wake cycle of the subject being studied. But there may be discrepancy between both these studies especially in young males whose actigraphic estimates of wake after sleep onset (WASO) were substantially greater than sleep diary estimates (74 min actigraphy vs. 7 min sleep diary) [2]. In children, actigraphic estimates of total sleep time is substantially less than sleep diary and parental report (6 h 51 min actigraphy vs. 8 h 16 min sleep diary v 8 h 51 min parent report).