Supplementing sleep actigraphy with button pressing while awake

Wrist-worn sleep actigraphs are limited for evaluating sleep, especially in sleepers who lie awake in bed without moving for extended periods. Sleep logs depend on the accuracy of perceiving and remembering times of being awake. Here we evaluated pressing an event-marker button while lying awake under two conditions: self-initiated pressing every 5 to 10 minutes or pressing when signaled every 5 minutes by a vibration pulse from a wristband. We evaluated the two conditions for acceptability and their concordance with actigraphically scored sleep.

Twenty-nine adults wore actigraphs on six nights. On nights 1 and 4, they pressed the marker to a vibration signal, and on nights 2 and 5, they self-initiated presses without any signal. On nights 3 and 6, they were told not to press the marker. Every morning they filled out a sleep log about how they had slept.

The vibration band was unacceptable to 42% of the participants, who judged it too disturbing to their sleep. Self-initiated pressing was acceptable to all, although it reduced log reported sleep depth compared to a no pressing condition. Estimations of sleep onset latency were considerably longer by button pressing than by actigraphy. Agreement of epoch-by-epoch sleep scoring by actigraphy and by button pressing was poor (kappa = 0.23) for self-initiated pressing and moderate (kappa = 0.46) for pressing in response to a vibration.

Self-initiated button pressing to indicate being awake while lying in bed is acceptable to many, interferes little with sleep, and adds substantially to the information given by actigraphy.