Importance: Cardiorespiratory fitness (hereinafter referred to as fitness) as estimated by exercise testing is a modifiable risk factor independently associated with chronic diseases, cardiovascular disease (CVD) events, and mortality, but the association of fitness at midlife with incidence of later-life depression and the risk of CVD mortality after a depression diagnosis is unknown.
Objective: To determine whether fitness measured in midlife would be inversely associated with later-life CVD mortality with antecedent depression.
Design, setting, and participants: This retrospective cohort study at a single-center, community-based preventive medicine clinic was performed as part of the Cooper Center Longitudinal Study. Data were collected from January 13, 1971, through December 31, 2009, and analyzed from October 6, 2015, through August 14, 2017. Participants included generally healthy men and women who presented for preventive medicine examinations at midlife and who were eligible for Medicare from 1999 to 2010. Those with a self-reported history of depression, myocardial infarction, or stroke at examination were excluded.
Exposures: Objective midlife fitness estimated from results of treadmill exercise testing.
Main outcomes and measures: Depression diagnosis from Medicare claims files using established algorithms and CVD mortality from National Death Index records.
Results: A total of 17 989 participants (80.2% men) with a mean (SD) age of 50.0 (8.7) years were included. After 117 218 person-years of Medicare follow-up, 2701 depression diagnoses, 610 deaths due to CVD without prior depression, and 231 deaths due to CVD after depression were observed. A high level of fitness in midlife was associated with a 16% lower risk of depression (hazard ratio [HR], 0.84; 95% CI, 0.74-0.95) compared with a low level of fitness. A high fitness level was also associated with a 61% lower risk of death due to CVD without depression (HR, 0.39; 95% CI, 0.31-0.48) compared with a low level of fitness. After a diagnosis of depression, a high fitness level was associated with a 56% lower risk of death due to CVD (HR, 0.44; 95% CI, 0.31-0.64) compared with a low fitness level.
Conclusions and relevance: Midlife fitness is associated with a lower risk of later-life depression, CVD mortality, and CVD mortality after incident later-life depression. These findings suggest the importance of midlife fitness in primary prevention of depression and subsequent CVD mortality in older age and should encourage physicians to consider fitness and physical activity in promoting healthy aging.