Impact of ambient temperature on mental health in Bern, Switzerland: a time-series study

Abstract

Abstract Background Previous studies suggest that people with mental disorders are more vulnerable to increased ambient temperatures (AT). In Switzerland, neuropsychiatric diseases contribute up to 35.1% of the total burden of disease. This burden could possibly increase in the future under current climate change scenarios, if no appropriate public health measures were implemented. However, there is lack of evidence on the impact of AT on mental health in Switzerland. Objective This study aimed to investigate the short-term association between AT and mental health hospitalizations in Bern, Switzerland. Methods From 1973 to 2010, we collected individual data on daily hospitalizations for mental disorders (71,931) from the University Hospital of Psychiatry and Psychotherapy in Bern. We used population-weighted daily mean AT for the canton of Bern derived from the 2.2-km gridded weather data provided by MeteoSwiss. We applied conditional Poisson regression with distributed lag linear models to assess the association and to account for delayed effects up to 3 days after the exposure. We conducted stratified analysis and by age, sex and diagnosis. Results The overall risk of hospitalizations increased linearly by 3.0% (95% CI: 0.0%, 6.0%) for every 10C°C-increase in mean daily AT. No differences in risk estimates were found across sex (3.0% in males (95% CI: 0%, 7.0%) and 4.0% in females (95% CI: 0%, 8.0%)) and age groups (≥ 45 years old: 4.0% (95% CI: 0%, 9.0%) and <45 years old: 3.0% (95% CI 0%, 7%)). Larger association estimates were found for schizophrenia (10.0%; 95% CI 4%, 16%), while no association was found for substance abuse (0.0%; 95% CI -7.0%, 6.0%). Conclusions Our preliminary findings suggest that increasing AT are associated with an increased risk in hospitalizations due to mental disorders in Bern. Specific public health policies should be urgently implemented in order to protect this vulnerable population sub-group from the challenges of climate change. Key messages Increased ambient temperatures are associated with an increased risk in hospitalizations due to mental health disorders. Specific health policies should be implement to protect mental health patients from the challenges of climate change.