Association between air pollution and suicide: a time series analysis in four Colombian cities

Background: Recent epidemiological studies have suggested that air pollution could be associated with suicide. However, other studies have criticized these results for being analytically weak and not taking into account potential confounding factors. As such, further studies examining the relationship under diverse contexts are necessary to help clarify this issue. This study explored the association between specific air pollutants (NO2, SO2, PM10, PM25, CO and O-3) and suicide incidence in four Colombian cities after adjusting for climatic variables and holidays Methods: A time series of daily suicides among men and women living in Bogota, Medellin, Cali and Bucaramanga was generated using information from the National Administrative Department of Statistics (DANE) for the years 2011-2014. At the same time, the average daily concentration of each air pollutant for each city was obtained from monitoring stations belonging to the National Air Quality Surveillance System. Using this information together, we generated conditional Poisson models (stratified by day, month and year) for the suicide rate in men and women, with air pollutants as the principal explanatory variable. These models were adjusted for temperature, relative humidity, precipitation and holidays. Results: No association was found between any of the examined pollutants and suicide: NO2 (IRR:0.99, 95% CI: 0.95-1.04), SO2 (IRR:0.99, 95% CI: 0.98-1.01), PM10 (IRR:0.99, 95% CI:0.95-1.03), PM2.5 (IRR:1.01, 95% CI: 0.98-1.05), CO (IRR:1.00, 95% CI:1.00-1.00) and O-3 (IRR: 1.00, 95% CI: 0.96-1.04). In the same way, no association was found in stratified models by sex and age group neither in lagged and cumulative effects models. Conclusions: After adjusting for major confounding factors, we found no statistically significant association between air pollution and suicide in Colombia. These "negative" results provide further insight into the current discussion regarding the existence of such a relationship.