Fig. 1.

Mean prevalence of short sleep duration over race/ethnic group, adjusted for age: Alameda County Health and Ways of Living Study, 1965–1999. Sample size and response rate for each follow-up were as follows: 1974 (n = 4,864; 85%), 1983 (50% of random sample of eligible subjects, n = 1,799; 87%), 1994 (n = 2,730; 93%), and 1999 (n = 2,123; 95%). Short sleep at baseline was calculated across categories for each covariate, including frequency, prevalence, and odds ratio. A generalized estimating equation approach for statistical testing with regard to short sleep, race/ethnic group, income, and education was used owing to the repeated nature of the data (10). African Americans (P < 0.0001) and Hispanics (P < 0.001) showed significantly greater increase over time in the prevalence of short sleep duration compared with whites. (Reprinted from ref. 10, Copyright 2007, with permission from Elsevier.)