Depression, Physical Function, and Risk of Mortality: National Diet and Nutrition Survey in Adults Older Than 65 Years

Objective: The authors used an objective assessment of physical function and a range of sociodemographic, dietary, and health behaviors to explore the possible factors that could explain the association between depression and mortality in community-dwelling elderly participants aged 65 years and older. Design: Prospective follow-up of the National Diet and Nutrition Survey in older adults. Setting: Community sample. Participants: A total of 1,007 participants (522 men, 485 women; mean age: 76.4 +/- 7.3 years). Measurements: Depression was assessed from the 15 item Geriatric Depression Scale (GDS) and physical function using hand grip strength. Participants were followed up for death over an average of 9.2 years. Results: At baseline, 20.9% of participants demonstrated depression (GDS-15 score >= 5). Depressed participants were at a higher relative risk of all cause mortality during follow-up (age-and sex-adjusted hazard ratio = 1.24, 95% confidence interval: 1.04-1.49). Other risk factors for depression also related to mortality included smoking, physical inactivity, and low grip strength. These factors collectively explained an estimated 54% of the association between depression and mortality. Low-grade inflammation and low plasma vitamin C were also independently associated with depression and mortality but did not explain any of the association between depression and mortality. Conclusion: Late-life depression is associated with a higher risk of mortality. Physical inactivity and physical dysfunction might partly mediate this association, although further longitudinal studies are required to fully elucidate these mechanisms. (Am J Geriatr Psychiatry 2010; 19:72-78)