Does obstructive sleep apnea confound sleep architecture findings in subjects with depressive symptoms?

BACKGROUND Compared with normal subjects, depressed patients have shorter rapid eye movement sleep latency (REML), increased REM and decreased slow wave sleep as a percentage of total sleep time (REM%, SWS%), and longer sleep latency (SL). Obstructive sleep apnea (OSA) patients experience longer REML, decreased REM% and SWS%, and shorter SL. We examined the interplay of depressive symptoms, OSA, and sleep architecture. METHODS Subjects (n = 106) were studied with polysomnography. OSA was defined as a Respiratory Disturbance Index > or = 15. Subjects were divided into Hi/Lo groups using a Center for Epidemiological Studies-Depression (CES-D) score of 16. RESULTS OSA patients had shorter SL than non-OSA patients (14.5 vs. 26.8 min, p <.001); Hi CES-D subjects showed a trend toward longer SL than Lo CES-D subjects (23.7 vs. 17.5 min, p =.079). Significant OSA x CES-D interactions emerged, however, for REM% (p =.040) and SL (p =.002): OSA/Hi CES-D subjects had higher REM% than OSA/Lo CES-D subjects (19.3% vs. 14.3%, p =.021); non-OSA/Hi CES-D subjects had SL (35.3 min) 2-3 times as long as other subjects (p =.002-.012). CONCLUSIONS Because of the high prevalence of OSA and depression, findings suggest that OSA must be considered in studies of mood and sleep architecture. Conversely, depressive symptoms must be considered in studies of OSA and sleep architecture.