The association between cardio-respiratory fitness and incident depression: The Maastricht Study

BACKGROUND: Moderate to vigorous physical activity (MVPA) can help to prevent depression, but identification of the most important psycho-biological pathways involved is unclear. The improvement of cardio-respiratory fitness (CRF) in response to MVPA can vary markedly, we therefore examined the association between CRF and the incidence of depressive symptoms. METHODS: We used data from The Maastricht Study, a large population-based prospective-cohort study. CRF was estimated at baseline from a graded submaximal exercise protocol and MVPA was measured with accelerometry. Depressive symptoms were assessed using the validated Dutch version of the 9-item Patient Health Questionnaire, both at baseline and during annual follow-up over five years. Cox proportional hazards models were used. RESULTS: A total of 1,730 individuals without depressive symptoms at baseline were included in the analysis. During the 5-year follow-up, n = 166 (9.6%) of individuals developed depressive symptoms. Compared to individuals with a low CRF, those with a moderate-to-high CRF had a significantly lower risk of developing depressive symptoms, independent of MVPA (medium CRF: HR = 0.49 (95%CI = 0.33-0.72); high CRF: HR = 0.48 (95% CI = 0.30-0.75). These associations were adjusted for age, sex, level of education, diabetes status, smoking status, alcohol use, energy intake, waist circumferences and antidepressant medications. LIMITATIONS: PHQ-9 is a validated screening instrument, but it is not a diagnostic tool of depression. CONCLUSIONS: Higher CRF was strongly associated with a lower risk of incident depressive symptoms over 5-year follow-up, independent of the level of MVPA at baseline, suggesting that interventions aimed at improving CRF could reduce the risk of depression.