Systematic review and meta-analysis for suicide associated with air pollution and ambient temperature

Abstract

BACKGROUND AND AIM Study results for air pollution, ambient temperature, and suicide are inconclusive. Given the health threats of climate change, a comprehensive review of the impacts of temperature and air pollution on suicide is needed with a focus on disparities of risks by population characteristics such as income and baseline health risks. We performed a systematic review and meta-analysis for suicide risks associated with short-term exposure to temperature and air pollution. METHODS Pubmed, Scopus, and Web of Science were searched for English-language publications using relevant keywords. Observational studies assessing risks of daily suicide and suicide attempts associated with temperature, particulate matter (PM₁₀, PM₂.₅), ozone (O₃), sulfur dioxide (SO₂), nitrogen dioxide (NO₂), and carbon monoxide (CO) were included. Random-effect meta-analysis pooled risk ratios (RRs) for daily suicide for an interquartile range (IQR) increase in exposure. Meta-regression analysis examined effect modification by income level based on gross national income (GNI) per capita, national suicide rates, and average level of exposure factors. RESULTS In summary, 18 studies for air pollution and 32 studies for temperature across 24 countries were included. RRs of suicide per IQR increase in temperature, PM₂.₅, PM₁₀, and NO₂ were 1.09 (95% CI: 1.06–1.13), 1.02 (95% CI: 1.00–1.05), 1.01 (95% CI: 1.00–1.03), and 1.03 (95% CI: 1.00–1.07), respectively. O₃, SO₂, and CO were not associated with suicide. RR of suicide was significantly higher in lower-income than higher-income countries (1.20, 95% CI: 1.14–1.26 vs. 1.09, 95% CI: 1.07–1.11 per 7.1°C increased temperature). Suicide risks associated with air pollution did not significantly differ by income level, national suicide rates, or average exposure levels. CONCLUSIONS Suicide was associated with temperature, PM, and NO₂. research gaps were found for addressing the interactions between air pollution and temperature on estimating suicide risks, which warrants future studies. Keywords Air pollution, climate change, suicide, temperature, meta-analysis.