Cardiovascular fitness in males at age 18 and risk of serious depression in adulthood: Swedish prospective population-based study.

Background Studies suggest a role for cardiovascular fitness in the prevention of affective disorders. Aims To determine whether cardiovascular fitness at age 18 is associated with future risk of serious affective illness. Method Population-based Swedish cohort study of male conscripts ( n = 1 117 292) born in 1950–1987 with no history of mental illness who were followed for 3–40 years. Data on cardiovascular fitness at conscription were linked with national hospital registers to calculate future risk of depression (requiring in-patient care) and bipolar disorder. Results In fully adjusted models low cardiovascular fitness was associated with increased risk for serious depression (hazard ratios (HR) = 1.96, 95%, CI 1.71–2.23). No such association could be shown for bipolar disorder (HR = 1.11, 95% CI 0.84–1.47). Conclusions Lower cardiovascular fitness at age 18 was associated with increased risk of serious depression in adulthood. These results strengthen the theory of a cardiovascular contribution to the aetiology of depression.