Suicide and transportation noise: a prospective cohort study from Switzerland

Abstract

Background: Evidence for effects of transportation noise on mental health remains scarce, mainly due to a lack of high quality studies. Meanwhile, psychiatric diseases are among the most prevalent non-communicable diseases worldwide, and suicide as a mortality outcome presents a pressing public health issue. The aim of this study is to investigate the association between transportation noise and suicide, while adjusting for air pollution. Methods: Road traffic, railway and aircraft noise exposure as well as PM2.5 exposure were linked to 5.1 million participants 15 years or older in the Swiss National Cohort, accounting for their address history. Mean noise exposure in 5-year periods was calculated. Individuals were followed for up to 15-years (2001-2015). Time-varying Cox regression models were applied to total suicides and cause-specific suicide deaths. Models included all three noise sources, PM2.5 plus individual and spatial covariates including socio-economic status. Effect modification by sex was also explored. Results: During the follow-up, there were 11,265 suicide deaths. Road traffic and railway noise were associated with total suicides (Hazard ratio: 1.039 [95% CI: 1.015-1.064] and 1.022 [1.004-1.041] per 10dB Lden, respectively ), while no significant association was found for aircraft noise. Associations were stronger for females than males. The pattern was robust across all outcomes, with the strongest association seen in non-violent suicides (poisoning: HR 1.122 [1.042-1.209] per 10dB Lden road traffic noise). No robust association was observed for PM2.5, whether adjusted for noise or separately. Conclusion: In this longitudinal, nationwide cohort study, we report a robust association between exposure to road traffic and railway noise and an increased risk for death by suicide. These findings add to the growing body of evidence that mental health disorders may be related to transportation noise exposure. Keywords : road traffic, railway, aircraft, Lden, air pollution, mental health