Ambulatory Evaluation of Sleep Disturbance and Therapeutic Effects in Sleep Apnea Syndrome by Wrist Activity Monitoring

A new wrist actometer was used to obtain ambulatory activity-rest recordings in 18 patients with sleep apnea syndrome (SAS) and in 22 control subjects. A movement index (MI) and a fragmentation index (FI) during sleep time were computed, giving an estimate of the stability of sleep. In control subjects, we observed a clear differentiation between night and day activity levels. The distribution of MI and FI was very narrow, with a mean +/- SD of 13.9 +/- 5.4 and 16.1 +/- 5.8%. No correlation of MI and FI with body mass index, even in heavily obese subjects, was found; MI and FI decrease significantly with age. A diagnosis of SAS was made by standard all-night polysomnography. Patients with SAS had a significantly higher MI and FI than did control subjects (p less than 0.001). With respect to polysomnographic diagnosis of SAS, the sensitivity of activity recordings was 89%, whereas the specificity was 95%. Five patients were studied after treatment, and decreases in MI and FI at home were in good agreement with the improvement in their sleep as assessed clinically and by polysomnography. We conclude that this technique is useful for an objective measurement of sleep restlessness and fragmentation, and for a simple evaluation of therapeutic effects under real life conditions in SAS.