Does air pollution trigger suicide? A case-crossover analysis of suicide deaths over the life span

In addition to underlying health disorders and socio-economic or community factors, air pollution may trigger suicide mortality. This study evaluates the association between short-term variation in air pollution and 10 years of suicide mortality in Belgium. In a bidirectional time-stratified case-crossover design, 20,533 suicide deaths registered between January 1st 2002 and December 31st 2011 were matched by temperature with control days from the same month and year. We used municipality-level air pollution [particulate matter (PM₁₀) and O₃ concentrations] data and meteorology data. We applied conditional logistic regression models adjusted for duration of sunshine and day of the week to obtain odds ratios (OR) and their 95% CI for an increase of 10 µg/m³ in pollutant concentrations over different lag periods (lag 0, 0-1, 0-2, 0-3, 0-4, 0-5, and 0-6 days). Effect modification by season and age was investigated by including interaction terms. We observed significant associations of PM₁₀ and O₃ with suicide during summer (OR ranging from 1.02 to 1.07, p-values <0.05). For O₃, significant associations were also observed during spring and autumn. Age significantly modified the associations with PM₁₀, with statistically significant associations observed only among 5-14 year old children (lag 0-6: OR = 1.45; 95% CI: 1.03-2.04) and ≥85 years old (e.g. lag 0-4: OR = 1.17; 95% CI: 1.06-1.29). Recent increases in outdoor air pollutants such as PM₁₀ or O₃ can trigger suicide, particularly during warm periods, even at concentrations below the European thresholds. Furthermore, PM₁₀ may have strong trigger effects among children and elderly population.