Background: Prospective 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.
Methods: In 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.
Results: There 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.
Limitations: Information on proximal causes, such as prior suicidal ideation, emotional distress and depression, was lacking at baseline.
Conclusions: Poor respiratory function in middle-aged men was an independent risk factor for completed suicide.