Sleep complaints and depression in an aging cohort: A prospective perspective

Objective: Most research on the association between sleep disturbances and depression has looked at cross-sectional data. The authors used two waves o f data from a panel study of community residents aged 50 years or more to i nvestigate this issue prospectively. Method: Data on symptoms of major depr essive episodes and sleep problems were examined for a subgroup of the 1994 and 1995 surveys of the Alameda County (California) Study (N=2,370). The a uthors examined the effects of age, gender, education, marital status, soci al isolation, functional impairment, financial strain, and alcohol use. Dep ression was measured with 12 items that covered the DSM-IV diagnostic crite ria for major depressive episodes, including insomnia and hypersomnia. Resu lts: The prevalences were 23.1% for insomnia and 6.7% for hypersomnia in 19 94. Sleep was a significant correlate of depression, as were being female, older age, social isolation, low education, financial strain, and functiona l impairment, When sleep problems and depression were examined prospectivel y, with controls for the effects of the other variables, sleep problems in 1994 predicted depression in 1995. However, other symptoms of major depress ive episodes-anhedonia, feelings of worthlessness, psychomotor agitation/re tardation, mood disturbance, thoughts of death-were much stronger predictor s of future major depression. Conclusions: Sleep disturbance and other symp toms that are diagnostic for major depression are strongly associated with the risk of future depression. Sleep disturbance appears to be a less impor tant predictor of depression. More epidemiologic research is needed on the relative contributions of the range of depressive symptoms to the risk of c linical depression.