Study finds hospital mortality from respiratory disorders is linked to ambient temperature

This is the major finding of a study published in The Lancet Regional Health - Europe by the Barcelona Institute for Global Health (ISGlobal), a centre financed by the "la Caixa" Foundation. The findings could aid healthcare facilities in adapting to climate change.

Between 2006 and 2019, the researchers looked at the relationship between ambient temperature and in-hospital mortality from respiratory disorders in the provinces of Madrid and Barcelona.

The number of hospital admissions (including those resulting in death) was higher in the cold season and lower in the summer season in both sites, with a peak in January and a low in August. In contrast to increasing hospital admissions during the winter season, the highest rate of inpatient mortality occurred during the summer and was closely associated with high temperatures.

The researchers used data on daily hospital admissions, weather (temperature and relative humidity), and air pollutants (O3, PM2,5, PM10, and NO2) to calculate the relationship between ambient temperature and hospital mortality. Although it is well known that daily exposure to heat and cold is associated with an increased risk of hospitalisation for a variety of respiratory diseases such as pneumonia, chronic obstructive pulmonary disease (COPD), and asthma, no study has focused on the proportion of hospital admissions that result in death, and thus the more severe cases.

The heat effect was instantaneous, with the majority of the damage occurring during the first three days of high-temperature exposure.

"This suggests that the increase in acute respiratory outcomes during heat is more related to the aggravation of chronic and infectious respiratory diseases than to the spread of new respiratory infections, which usually take several days to cause symptoms," said Hicham Achebak, first author of the study and researcher at Inserm and ISGlobal, who holds a Marie Sklodowska-Curie Postdoctoral Fellowship from the European Commission.

on acute bronchitis and bronchiolitis, pneumonia and respiratory failure. Neither relative humidity nor air pollutants played a statistically significant role in the association of heat with mortality in patients admitted for respiratory disease. The research also showed that women were more vulnerable to heat than men.

"This is most likely due to specific physiological differences in thermoregulation. Women have a higher temperature threshold above which sweating mechanisms are activated, and a lower sweat output than men, which results in less evaporative heat loss, and therefore greater susceptibility to the effects of heat," explained Joan Ballester, ISGlobal researcher and last author of the study.

The study shows that high temperatures contributed to an increase in the risk of fatal hospital admissions, especially in Barcelona, whereas low temperatures were not associated with this variable. According to the research team, this might have to do with the fact that health services are increasingly prepared to deal with winter peaks in respiratory diseases.

In this sense, the findings have important implications for health adaptation policies to climate change, and for projections of the impact of climate change on human health. "Unless effective adaptation measures are taken in hospital facilities, climate warming could exacerbate the burden of inpatient mortality from respiratory diseases during the warm season," said Hicham Achebak. (ANI)