High temperatures trigger suicide mortality in Brussels, Belgium: A case-crossover study (2002-2011)

Background: Temperature may trigger the risk of suicide, however, the extent and shape of the associations show geographical variation. Here, we investigate the short-term effects of temperature on suicide deaths occurring in Brussels between January 1st, 2002 and December 31st, 2011. Methods: We conducted a bidirectional time-stratified case-crossover study with cases being suicide deaths occurring among Brussels residents aged 5 years or older. Cases were matched by day of the week with control days from the same month and year. The exposure was the daily average temperature measured at the Uccle station (Brussels) and obtained from the Belgian Royal Meteorological Institute. We combined conditional logistic regression with distributed lag non-linear models (DLNM) to obtain one week (lag 0-6) cumulative risk ratios (RR) and their 95% confidence intervals (CI) for the effects of moderate and extreme cold (5th and 1st percentiles of temperature, respectively) and moderate and extreme heat (95th and 99th percentiles of temperature, respectively), relative to the median temperature. Results: In total, 1891 suicide deaths were included. The median temperature was 11.6 degrees C, moderate and extreme cold temperatures were 0 and -3.1 degrees C, respectively, and moderate and extreme high temperatures were 20.9 and 24.4 degrees C, respectively. The cumulative risk of suicide mortality was almost twice higher among lags 0 to 6 for both moderate and extreme heat, relative to the period median temperature (e.g. moderate heat RR = 1.80 CI:1.27-2.54). No statistically significant associations were observed for cold temperatures. Conclusions: In Brussels, a western European city with temperate climate, high temperatures may trigger suicide deaths up to one week later. In the context of climate change, adaptation strategies must take into consideration the effects of temperature on mental health.