Low Respiratory Function Increases the Risk of Depressive Symptoms in Later Life in Men

Objective: To assess the risk of depressive symptoms with respect to respiratory function in middle-aged men. Chronic lung diseases are associated with a high prevalence of depression, but the association of poor respiratory function with depressive symptoms has not been established in prospective population-based cohort studies. Methods: In a prospective, population-based cohort study with up to 30 years of follow-up, we included 1205 men aged 50 to 69 years from Finland (n = 663) and Italy (n = 542). Forced vital capacity (FVC) and forced expiratory flow in 0.75 sec (FEV0.75) in 1970 were analyzed in relationship to depressive symptoms (by Zung self-rating depression scale [SDS]) in 1985, 1990, 1995, and 2000, using multilevel regression models. Subsequent analyses were done separately in the strata with (n = 501) and without (n = 704) chronic diseases in 1970 (i.e., chronic lung diseases, cardiovascular diseases, or diabetes mellitus). Results: Poor respiratory function was associated independently with steeper increases in depressive symptoms over time, both for FVC (p < .001) and FEV0.75 (p = .004). In participants without chronic diseases, a standard deviation (SD) increase in FVC was associated with a 1.1-point decrease (standard error [SE] = 0.4) in Zung SDS (p = .01) and a 1.5-point decrease (SE = 0.4) (p < .001) in participants with chronic diseases (p = .27 for interaction). Low FEV0.75 was associated with more depressive symptoms in participants with chronic diseases (1.7 SE 0.4 decrease per SD; p < .001), but not in participants without chronic diseases (0.6 SE 0.4 decrease per SD; p = .16; p = .008 for interaction). Conclusions: Small lung volumes were associated with an increased risk of subsequent depressive symptoms at old age, especially in persons with chronic lung diseases, cardiovascular diseases, or diabetes mellitus at baseline.