The Effect of High Summer Temperatures on Emergency Hospital Admissions in Switzerland: A Comparison to Heat-Related Mortality

Abstract

Background. While previous studies showed a clear association between high temperatures and mortality in Switzerland, the effect of heat on morbidity is less well understood. To evaluate how hot weather affects morbidity in Switzerland and how it compares to heat-related mortality, we assessed a) cause-specific morbidity during the hot summer 2015, and b) the relationship between heat and emergency hospital admissions (EHA) between 2006 and 2015.Methods. Daily EHA during the summer 2015 (June-August) were analysed in relation to comparison periods. For aim b) daily relationships between day-time maximum (Tmax) temperature and EHA during the warm season (May-September) 2006 to 2015 were assessed for different diagnoses and age groups by applying conditional Poisson regression models combined with Non-Linear Distributed lag models. Results were compared to our similar analyses on heat-related mortality.Results. Overall, we estimated an increase in EHA (non-external causes) by 2.6% (95%CI: 0.2-5.0) during the summer 2015. For the same period, an excess mortality of 5.4% (3.0-7.9%) was estimated. Between 2006 and 2015 an increase in Tmax from the median (22°C) to the 98th percentile (33°C) was associated with an overall 3% increase in EHA over the following four days (relative risk (RR) of 1.03 (95% CI: 1.02-1.05)). Larger increases were observed for respiratory (1.20 (1.09-1.31)) and renal diseases (1.21 (1.04-1.40)) in people aged ≥74 years, and for infection-related EHA, mainly in children <15 years old (1.24 (1.11-1.37)). In contrast to heat-related mortality, no significant association between Tmax and cardiovascular EHA was found.Conclusions. Our results indicate that increases in ambient temperature during summer months have important impacts on morbidity. In general, the impact was smaller than what was observed for heat-related mortality. Nevertheless, current public health strategies can greatly be improved when targeting measures to both groups of outcomes.