Rising temperatures heighten risk for asthma hospitalizations in summer

Key takeaways:

• The impact of the relationship between asthma hospitalization and warm temperatures was stronger in males vs. females.
• As years pass, this effect is slowly declining.

In England, the risk for hospitalization for asthma in the summer was heightened when temperatures rose, according to results published in Thorax.

“This study provides evidence of an association between warm temperature and hospital admission for asthma,” Garyfallos Konstantinoudis, PhD, Medical Research Council skills development research fellow in the department of epidemiology and biostatistics at Imperial College London, and colleagues wrote. “The effect has decreased over time with potential explanations including temporal differences in patterns of heat exposure, adaptive mechanisms, asthma management, lifestyle, comorbidities and occupation.”

In a case-crossover study, Konstantinoudis and colleagues used NHS Digital Hospital Episode Statistics data to evaluate 260,085 asthma hospitalizations (age 16-64 years, n = 135,011; females, n = 81,336) that occurred during in the months of June, July and August from 2002 to 2019 in England at high temporal (daily) and spatial (postcodes) resolutions to see if warm temperatures are related to these hospitalizations. Researchers averaged the daily mean temperatures (at 1 km x 1 km resolution) from the 3 days before hospitalization to account for the delayed impact of heat exposure.

To adjust for potential confounding variables, such as rainfall, relative humidity, wind speed and national holidays, researchers used fitted Bayesian hierarchical Poisson models.

Over June, July and August, the mean of the mean daily temperature appeared comparable between the assessed years, with an average of 16°C in 2002-2007, 15.5°C in 2008-2013 and 16.1°C in 2014-2019.

With each additional 1°C in daily mean summer temperature, researchers observed that the risk for asthma hospital admittance went up by 1.11% (95% CI, 0.88%-1.34%).

When assessing this relationship by age and sex, males of all ages had a more elevated risk for hospitalization with every 1°C rise in temperature than girls/women, with males aged 16 to 64 years at greatest risk (2.1%; 95% CI, 1.59%-2.61%), according to researchers.

Notably, individuals aged 65 years and older in the total cohort showed very little increase in risk.

In terms of temporal trends, researchers found greater risk in 2002-2007 (2.96%; 95% CI, 2.56%-3.37%) than in 2008-2013 (–0.04%; 95% CI, –0.46% to 0.37%) and 2014-2019 (–0.01%; 95% CI, –0.39% to 0.37%), with 2002-2007 hospitalizations among males aged 16-64 years being the primary contributors to the increased risk, at 4.58% (95%CI, 3.71%-5.46%).

Researchers also conducted a post-hoc analysis and discovered an overall decreasing trend in this effect, so that with each year, the risk for hospital admittance with rising temperatures will decline by 0.22 (95% CI, –0.27 to –0.17).

“This study provides evidence of an association between warm temperatures and asthma exacerbations in England,” Konstantinoudis and colleagues wrote. “More studies in counties with different climate, health care and social behaviors are needed to further understand the generalizability of the results.

“The effect of warm temperatures on asthma hospitalization has attenuated over time suggesting potential adaptive mechanisms to heat exposure or differences in behaviors, lifestyle, comorbid conditions, other environmental exposures and occupation over time,” they added.