Disclosures: The authors report no relevant financial disclosures.
August 19, 2021
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Pneumonia in infancy increases risk for asthma at age 4 years

Disclosures: The authors report no relevant financial disclosures.
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In a new study, children with pneumonia diagnosed during infancy had an increased risk for asthma at age 4 years.

“Few studies have assessed the association between pneumonia and asthma, and the data is largely based on old birth cohorts of children born in the ’60s to ’80s, which might not be representative of children today given the changes in socioeconomic status, child immunization programs and tobacco control that have occurred over the last decades,” Samuel Rhedin, PhD, from the department of medical epidemiology and biostatistics at Karolinska Institute and the Sachs Children and Youth Hospital, Stockholm, told Healio. “Further, there has been a discussion whether certain children have a genetic predisposition for both pneumonia and asthma.”

Samuel Rhedin, PhD, quote
Data were derived from Rhedin S, et al. Chest. 2021;doi:10.1016/j.chest.2021.03.006.

The nationwide register-based cohort analysis included 948,045 children (51.3% boys) from Sweden. Of those, 23,086 (2.4%) were diagnosed with pneumonia at age 2 years or younger. Pneumonia episodes were classified as occurring during the pre-pneumococcal conjugate vaccine (PCV) period or during the PCV period.

The primary outcome was the association between pneumonia diagnosis during infancy and asthma prevalence at age 4 years. The secondary outcome was the association between pneumonia diagnosis during infancy and asthma at age 4 years and if there were changes after introducing the PCV immunization.

Samuel Rhedin, PhD

The results were published in Chest.

Researchers reported a strong association between pneumonia diagnosis during infancy and asthma at age 4 years (adjusted OR = 3.38; 95% CI, 3.26-3.51). This association remained in a subanalysis where siblings were used as controls (aOR = 2.81; 95% CI, 2.58-3.06), which the researchers performed to explore confounding from familial factors.

Asthma risk following pneumonia diagnosis during infancy was higher among children born during the PCV period (aOR = 3.8; 95% CI, 3.41-4.24) compared with children born in the pre-PCV period (aOR = 3.28; 95% CI, 3.15-3.42). The proportion of viral pneumonia etiology was higher for children born during the PCV period compared with those born during the pre-PCV period (14.5% vs. 10.7%; P < .001), which likely explained the increased risk for asthma among these children, as viral pneumonia previously has been more strongly associated with pneumonia, according to the authors.

“We were surprised by the strong association between pneumonia and asthma with odds ratios greater than 3. Almost one-fifth of all children experiencing pneumonia in infancy had asthma during their fifth year of life. This is important information to provide the parents to infants with pneumonia and suggests that asthma screening or some kind of follow-up should be considered,” Rhedin told Healio.

In addition, overall asthma prevalence was also lower among these children compared with children born in the pre-PCV period (5.3% vs. 6.6%; P < .001).

“This further supports the need for preventions targeting pneumonia and suggests that screening for asthma could be considered in this particular risk group,” Rhedin said. “Asthma is a disease that attributes to significant morbidity in children and additional studies on the origins of asthma are needed to further prevent the disease.”

For more information:

Samuel Rhedin, PhD, can be reached at samuel.rhedin@ki.se.