Diabetes, major depression, and functional disability among U.S. adults.

OBJECTIVE The goal of this study was to determine prevalence and odds of functional disability in individuals with diabetes and comorbid major depression compared with individuals with either diabetes or major depression alone. RESEARCH DESIGN AND METHODS Data on 30,022 adults aged > or = 18 years from the 1999 National Health Interview Survey (NHIS) were analyzed. Four disease categories were created: no diabetes and no major depression, major depression alone, diabetes alone, and diabetes and comorbid major depression. Prevalence of functional disability was calculated for each disease category. Multiple logistic regression was used to determine the odds and correlates of functional disability by disease category controlling for age, sex, race/ethnicity, education, income, census region, and disability-associated comorbidity. STATA was used for all analyses to account for the complex survey design of NHIS. RESULTS Irrevalence of functional disability by disease category was as follows: no diabetes and no major depression (24.5%); major depression (51.3%); diabetes (58.1%); and diabetes and comorbid major depression (77.8%). With no diabetes and no major depression as reference and after adjusting for relevant covariates, the odds of functional disability was 3.00 (95% CI 2.62-3.42) for major depression, 2.42 (2.10-2.79) for diabetes, and 7.15 (4.53-11.28) for diabetes and comorbid major depression. CONCLUSIONS Individuals with diabetes and comorbid major depression have higher odds of functional disability compared with individuals with either diabetes or major depression alone. Additional studies are needed to establish a causal relationship.