Incremental Increases in Non-Exercise Estimated Fitness Reduce Subsequent Depressive Symptoms

Abstract

The purpose of this observational retrospective cohort study was to examine the association between non-exercise estimated Cardiorespiratory Fitness (eCRF) and incident depressive symptoms. A total of 14,431 participants from the Aerobics Center Longitudinal Study cohort between February 5, 1979 and December 31, 1998, were followed for incident depressive symptoms through December 31, 1999. Depressive symptoms were determined by the CES-D 10 item questionnaire. eCRF in MET was determined from a non-exercise algorithm developed by Jackson and further grouped into sex-specific tertiles. Multivariable logistic regression was used to estimate odds ratios and 95% confidence intervals. 11.7% of men and 14.8% of women developed depressive symptoms after a mean of 12 follow- up years. In the overall sample, the odds ratio of depressive symptoms was 0.84 (95% CI 0.74-0.95) times lower in the middle eCRF tertile than in the lower tertile and was 0.74 (95% CI 0.66-0.85) times lower in the highest tertile. Each 1-MET increase in fitness reduced the odds ratio for depressive symptoms by 0.91 times (95% CI 0.89-0.93). The pattern of the association between eCRF and incident depressive symptoms was consistent between men and women, however, the magnitude of the risk reduction was smaller in women than in men. eCRF is a useful predictor of depressive symptoms. The non-traditional way of estimating CRF might provide more clinical utility compared to CRF measured using standard exercise protocols.