A team from the Barcelona Institute for Global Health, supported by the “la Caixa” Foundation and the French National Institute of Health and Medical Research (Inserm), has analysed the impact of high summer temperatures on hospital admissions in Spain over a decade. Published in Environmental Health Perspectives, their research spans data from over 11.2 million emergency hospital admissions between 2006 and 2019 across 48 provinces in mainland Spain and the Balearic Islands, sourced from the Spanish National Institute of Statistics. The study focused on daily mean temperatures, relative humidity, and concentrations of air pollutants (PM2.5, PM10, NO2, and O3), examining their correlations with various causes of hospitalisation during the summer months (June to September) and by province.
The findings highlight that metabolic disorders and obesity, renal failure, urinary tract infections, sepsis, urolithiasis, and drug poisoning were among the health issues most significantly impacted by high temperatures. The statistical analysis confirmed a widespread increase in cause-specific hospitalisations due to elevated temperatures. Vulnerability varied across age groups, with infants under one year and adults over 85 exhibiting the highest risk of hospital admission. Sex-specific differences also emerged, with men showing a heightened risk of hospitalisation for injuries during hotter days. In contrast, women faced increased risks related to parasitic, endocrine, metabolic, respiratory, or urinary diseases.
According to Hicham Achebak, a researcher at INSERM and ISGlobal and recipient of a Marie Sklodowska-Curie postdoctoral fellowship, the mechanisms through which heat triggers adverse health outcomes remain unclear but are linked to the body’s thermoregulation processes. “Under conditions of heat stress, the body initiates cutaneous vasodilation and sweat production to dissipate heat, which can affect individuals differently based on age, sex, or underlying health conditions,” Achebak explains. He notes that women, for instance, tend to have a higher temperature threshold for activating sweating mechanisms, rendering them more susceptible to heat-related effects.
The study underscores that individuals with obesity are particularly vulnerable to heat-related health issues due to less efficient heat loss responses, exacerbated by body fat acting as an insulator. Moreover, while relative humidity did not significantly influence the heat-related hospitalisation risk across most conditions, lower humidity amplified the risk of acute bronchiolitis. Air pollution and exceptionally high levels of PM2.5 and NO2 intensified the risks of hospitalisation for metabolic disorders, obesity, and diabetes, highlighting the multifaceted impact of environmental factors on health outcomes during high-temperature periods.
Joan Ballester Claramunt, an ISGlobal researcher and senior author of the study, emphasises the nuanced effects of heat waves, noting that while they marginally increased hospitalisation risks for certain diseases like non-respiratory infectious diseases, endocrine and metabolic disorders, and nervous system diseases, the study suggests that current Heat-Health Early Warning Systems should be activated not only during heat waves but also during periods of sustained extreme temperatures.
The study provides critical insights into how summer heat influences hospital admissions in Spain, revealing differential impacts across demographics and health conditions and emphasising the importance of tailored public health strategies to mitigate the health risks associated with rising temperatures.
More information: Hicham Achebak et al, Heat Exposure and Cause-Specific Hospital Admissions in Spain: A Nationwide Cross-Sectional Study, Environmental Health Perspectives. DOI: 10.1289/EHP13254
Journal information: Environmental Health Perspectives Provided by Barcelona Institute for Global Health – ISGLOBAL
