Respiratory function and other biological risk factors for completed suicide: 40 years of follow-up of European cohorts of the Seven Countries Study

BackgroundProspective cohort studies on biological risk factors of completed suicide are scarce. We aimed to test which biological risk factors independently identify subjects at increased risk of suicidal death.MethodsIn the prospective cohort of the Seven Countries Study, 5,321 middle-aged men from Finland, Serbia, Italy, and Greece were included. Completed suicide (ICD-8 codes E950-959) was assessed during 40 years of follow-up. Biological cardiovascular risk factors (including forced vital capacity [FVC] and height) were tested for their role as predictors in multivariable Cox models stratified by country.ResultsThere were 4518 deaths during follow-up, with 64 from suicide (1.4%). In univariable models, only FVC and height were strongly inversely related with suicide. Socio-economic status and being unmarried were potential confounders. In multivariable models taking these confounders into account, both a low FVC (0.30 for top vs. lowest quartile; 95% CI: 0.12–0.76; P = 0.006 for trend) and a low FVC/height ratio (0.37 for top vs. lowest quartile; 95% CI: 0.17–0.82; P = 0.004 for trend) were strongly inversely related with completed suicide.LimitationsInformation on proximal causes, such as prior suicidal ideation, emotional distress and depression, was lacking at baseline.ConclusionsPoor respiratory function in middle-aged men was an independent risk factor for completed suicide.