Age-related changes in sleep in depressed and healthy subjects. A meta-analysis

In this article we demonstrate that the difference in sleep between depressives and healthy controls varies systematically as a function of the mean age of the sample studied. The data were taken from 27 studies that had compared the sleep of drug-free depressed patients and age-matched healthy controls. In all, the studies give data for 822 patients (in 41 samples) and 621 healthy controls (in 37 samples). The mean age of the samples varied between 9 and 72 years. For total sleep time, minutes awake, sleep efficiency, minutes of slow-wave sleep, and REM latency, there are reliable age-related trends in both sets of samples. These trends follow a progressively diverging course such that, within studies, the mean difference and the standardized mean difference (d) between patients and controls increases as a linear function of the mean age of the former (i.e., the older the patients, the greater the difference). Possible reasons for the interaction are discussed.