National Sleep Foundation

Glossary

W

Wake After Sleep Onset (WASO) - The number of times a person wakes up during sleep, which increases with age.

Wrist Actigraph - A small device that monitors and analyses wrist movements during routine daily activities to estimate time spent sleep vs. awake. Wrist actigraphy provides a fair (although not exact) measurement of when, and for how long, a patient sleeps.