Adherence

Actigraphy has very low specificity (approx. 50%) for detecting wakefulness during sleep, leading to significant overestimation of total sleep time and sleep efficiency, particularly in conditions with fragmented sleep or high wake propensity.

Do not rely on actigraphy (wrist-worn trackers) to assess your sleep quality if you have insomnia, sleep apnea, or shift work. These devices will likely overestimate how much you slept because they mistake lying still while awake for sleep. Use them for general trends, but not for clinical decision-making or detailed sleep analysis.