Objective: To test the hypothesis that socioeconomic status (SES) would be associated with sleep quality measured objectively, even after controlling for related covariates (health status, psychosocial characteristics). Epidemiological studies linking SES and sleep quality have traditionally relied on self-reported assessments of sleep.
Methods: Ninety-four women, 61 to 90 years of age, participated in this study. SES was determined by pretax household income and years of education. Objective and subjective assessments of sleep quality were obtained using the NightCap sleep system and the Pittsburgh Sleep Quality Index (PSQI), respectively. Health status was determined by subjective health ratings and objective measures of recent and chronic illnesses. Depressive symptoms and neuroticism were quantified using the Center for Epidemiological Studies Depression Scale and the Neuroticism subscale of the NEO Personality Inventory, respectively.
Results: Household income significantly predicted sleep latency and sleep efficiency even after adjusting for demographic factors, health status, and psychosocial characteristics. Income also predicted PSQI scores, although this association was significantly attenuated by inclusion of neuroticism in multivariate analyses. Education predicted both sleep latency and sleep efficiency, but the latter association was partially reduced after health status and psychosocial measures were included in analyses. Education predicted PSQI sleep efficiency component scores, but not global scores.
Conclusions: These results suggest that SES is robustly linked to both subjective and objective sleep quality, and that health status and psychosocial characteristics partially explain these associations.
SES = socioeconomic status; PSQI = Pittsburgh Sleep Quality Index; GCRC = General Clinical Research Center; CES-D = Center for Epidemiological Studies Depression Scale.
From the Department of Population Health Sciences (E.M.F.), Robert Wood Johnson Health and Society Scholars Program; Institute on Aging (G.D.L., C.D.R.); Department of Psychology (M.A.R., R.J.D., C.D.R.), University of Wisconsin-Madison, Madison, Wisconsin; Department of Psychology (H.L.U.), Tufts University, Medford, Massachusetts; Office of Population Research (B.H.S.), Princeton University, Princeton, New Jersey.
Address correspondence and reprint requests to Elliot Friedman, Department of Population Health Sciences, 624 WARF Office Bldg., 610 N. Walnut Street, Madison, WI 53726. E-mail: email@example.com
Received for publication June 13, 2006; revision received May 16, 2007.
This research was supported by the Robert Wood Johnson Foundation (E.F.), Grant P01-AG020166 from the National Institute on Aging (C.R., B.S., G.L.), Grant P50-MH61083 from the National Institute of Mental Health (C.R., B.S., G.L., R.D., H.U.), and Grant M01-RR03186 from the National Institutes of Health (General Clinical Research Center, University of Wisconsin-Madison).