Low respiratory function increases the risk of depressive symptoms in later life in men

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.

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 (FEV(0.75)) 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).

Poor respiratory function was associated independently with steeper increases in depressive symptoms over time, both for FVC (p < .001) and FEV(0.75) (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 FEV(0.75) 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).

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.