The ISGlobal research included data from more than 11.2 million hospital admissions between 2006 and 2019, carried out through the Emergency Department in 48 Spanish provinces.
Faced with a future that holds more periods of exposure to high temperatures for our country, studying the impact of heat on populations most vulnerable is crucial to act accordingly. Experts want to measure the step prior to death: determine at what temperatures the risk of hospital admission increases and in what pathologies.
With this objective, a team from the Barcelona Institute for Global Health, a center promoted by the “la Caixa” Foundation, and the National Institute of Health and Medical Research (Inserm) of France, has prepared an analysis of the hospital admissions related to high summer temperatures in Spain for more than a decade.
What have they found? The research concludes that causes of hospitalization in which heat has a more notable impact are: disorders metabolic and related to obesity,renal insufficiencyurinary infection, sepsis, urolithiasispoisoning by drugs and other non-medicinal substances.
hicham Achebakresearcher at Inserm and ISGlobal and holder of a Marie Sklodowska-Curie postdoctoral fellowship from the European Commission, in a briefing held by SMC, commented, regarding the study carried out and which has seen the light in Environmental Health Perspectives, that dehydration is behind many of these alterations.
“In the endocrine diseasesintense heat is not directly behind its alterations,” Achebak explained. “Insufficient fluid consumption can cause dehydration and a condition of this type has an impact on the renal system: promoting the formation of kidney stones or lithiasis, and favoring the proliferation of chemical elements and bacteria in the urinary tract,” he explained.
And who are the groups most at risk? “Heat increases risk of hospitalization in all age groups,” stated the author of the work. Achebak mentioned the role of thermoregulation in establishing physiological differences. “It is well known that thermoregulatory capacity is not fully developed during the first years of life and deteriorates over time. naturally, for example.” That is why children under one year of age and those over 85 years of age They are the ones who enter the most due to the decompensations that the heat causes in them.
They were also found differences by sexsince on the hottest days the men showed a higher risk of hospitalization for injuries than women, while women had a higher risk of admission for parasitic, endocrine and metabolic, respiratory or urinary diseases.
“In conditions of thermal stress, The body activates cutaneous vasodilation and sweat production to lose heat. Subsequent reactions can affect people differently depending on a number of factors, such as age, gender or pre-existing health conditions,” Achebak said. “We know, for example, that women have a higher temperature threshold from which the mechanisms of sweating and are more susceptible to the effects of heat,” he said.
Furthermore, the expert emphasizes that It’s not about “those days of maximum temperatures“, limiting only to a specific period of time in heat waves. “We talk about those loose days” and “added effect of persistence, not consecutiveness“. And it is for this reason that its research group is committed to alerts that not only cover heat waves, “but also during those isolated days in which the temperature can reach very high values“.
How have you extracted the work data?
The work, published in Environmental Health Perspectivesincluded data from more than 11.2 million of hospital admissions between 2006 and 2019. These data were restricted to the admissions through emergency services from 48 provinces of mainland Spain and the Balearic Islands and were provided by the National Institute of Statistics of Spain.
The team also calculated the values of the average daily temperatures the RH daily average and the concentrations of different air pollutants (P.M2.5PM10, NO2 I3).
With the help of different models, they estimated the relationships between temperature and the different causes of hospitalization for the summer season (from June to September) and by province.
Attended to percentage increase in the probability of hospitalization In extreme summer temperatures compared to comfort temperatures, Zaragoza (16.6%), Gipuzkoa (16%) and Zamora (14.6%) are the three provinces with the highest figure. At the other extremes with a risk reduction of up to 8% are Asturias (8%), Tarragona (8.2%) and Córdoba (8.3%).
As expected, statistical analysis showed that high temperatures had “a widespread impact on hospitalizations for specific reasons.”
“The underlying mechanisms “Why heat triggers adverse health outcomes remains unclear, but appear to be related to the way our body regulates its own temperature,” he said. Achebak.
Here the ISGlobal expert also emphasized “physiological adaptation” as a defense mechanism developed generation after generation; because “when mortality has been analyzed, the risk of dying today from an extremely high or low temperature is lower than that of 20 years ago.” But Nowadays it is more about a “socioeconomic adaptation which allows us to face sudden changes with external elements, whether heating or air conditioning, in better conditions.
Obesity and metabolic disorders, main target
The group of diseases most affected by heat were metabolic disorders and obesity . The risk of hospital admission for this type of illness on the hottest days almost doubled compared to days of optimal temperature or comfort.
“There are several reasons for this. For example, in people with obesity, heat loss responses work less effectively, as body fat acts as an insulator, making them more susceptible to heat disorders.” , argument Achebak.
Other factors: Relative humidity, air pollution and heat waves
Regarding other variables included in the study, relative humidity did not seem to play a relevant role in the relationship between heat and urgent hospital admissions, except in the case of the risk of acute bronchitis and bronchiolitis which was higher on days with lower relative humidity.
Additionally, days of high air pollution appeared to exacerbate the risk of heat-related hospitalization for metabolic disorders and obesity as well as the diabetesbut not in the rest of the health outcomes.
“We observe that the added effects of heat waves –or extremely high temperatures for consecutive days– were small and specific to a subset of diseases, mainly non-respiratory infectious diseases, endocrine and metabolic disorders or diseases of the nervous system, among others. For this reason, we believe that current heat-health early warning systems should be activated not only during heat waves, but also during non-persistent extreme temperatures,” he says. Joan Ballester Claramunt ISGlobal researcher and last author of the study.