Actigraphy in older adults: comparison of means and variability of three different aggregates of measurement.

Actigraphy has emerged as a valuable method for measuring natural sleep patterns; however, it is unclear how many consecutive nights should be measured and what sleep parameter values are typical of older adults. This study examined sleep in relatively healthy community-based older adults for 14 consecutive days. The findings present comparison values for Actiwatch-L actigraphy in older adults, and can be used to determine an appropriate length of measurement. When using means of the aggregate period, a 3-day aggregate is comparable to the values obtained over 7- or 14-day aggregates. However, if variability of the sleep parameter is of interest, a minimum of a 7-day aggregate is needed, and 14-day aggregates are better when measuring sleep onset latency.