Early ozone exposure linked to elevated odds for asthma, wheeze in early childhood
Key takeaways:
- Researchers found heightened odds for asthma and wheeze at age 4 to 6 years as ozone between birth and age 2 years increased.
- Early ozone exposure was not linked to asthma or wheeze at age 8 to 9 years.
As average ozone exposure in the first 2 years of life rose, so did the likelihood for caregiver-reported asthma and wheeze in children aged 4 to 6 years, according to results published in JAMA Network Open.
“These findings highlight the role that air pollution and environmental contaminants play on the development of airways disease in children,” Logan C. Dearborn, MPH, graduate research assistant and research consultant in the department of environmental and occupational health sciences at University of Washington, told Healio.
“It is important for clinicians to be aware of, and convey to their patients, how air pollution influences health,” he continued. “Helping patients be aware of the air quality index and the actions that are recommended to reduce exposure to harmful air is a vital way clinicians can promote the prevention of airways disease in children.”
Using 2007 to 2023 data from the ECHO-PATHWAYS consortium, Dearborn and colleagues evaluated 1,188 children (51.7% female) from six U.S. cities to uncover if ambient ozone exposure up to age 2 years is linked to caregiver-reported asthma and wheeze at two age ranges: 4 to 6 years and 8 to 9 years.
Researchers additionally assessed whether ozone plus fine particulate matter (PM2.5) and nitrogen dioxide exposure is linked to asthma and wheeze in the outlined age ranges.
“Ozone is of particular concern since it is the air pollutant that most frequently exceeds current regulatory thresholds, and asthma remains a leading chronic disease in children,” Dearborn told Healio. “This means that increased attention aimed at reducing childhood ozone exposures is crucial.”
On average, ozone was found to have a concentration of 26.1 parts per billion (ppb), and this was “relatively low,” according to the study.
Within the total cohort, less than 16% of children aged 4 to 6 years had asthma (12.3%) and wheeze (15.8%) per caregiver reports.
Researchers found that as the average ozone concentration in the first 2 years of life went up by 2 ppb, so did the adjusted likelihood for caregiver-reported asthma at age 4 to 6 years (adjusted OR = 1.31; 95% CI, 1.02-1.68).
The same pattern was observed during the evaluation of the odds for caregiver-reported wheeze, with heightened adjusted odds at age 4 to 6 years as ozone concentration between birth and 2 years old increased (aOR = 1.3; 95% CI, 1.05-1.64).
According to the study, the above odds ratios accounted for several covariates: child sex, age, birth year, site, maternal education, maternal asthma status, postnatal secondhand smoke exposure and neighborhood deprivation index.
“Our primary finding, that early-life ozone was associated with asthma in early childhood, was well supported by the animal toxicologic evidence that suggested early life as a critical period of airways development,” Dearborn told Healio.
In contrast, researchers reported that early ozone exposure was not linked to caregiver-reported asthma or wheeze at age 8 to 9 years.
“What we were perhaps most surprised by was the large risk associated with a small difference in long-term ozone as well as our null findings for asthma at ages 8 to 9,” Dearborn told Healio. “While we hypothesize that additional and more proximal risk factors are more relevant for asthma later in childhood, more research investigating early-life ozone on asthma across childhood is needed.”
Switching to the analysis of ozone in combination with PM2.5 and nitrogen dioxide, caregiver-reported asthma at age 4 to 6 years continued to be linked to an elevated ozone concentration (25 to 28 ppb) when PM2.5 and nitrogen dioxide were held to their median values, according to the study. This was also true for caregiver-reported wheeze at age 4 to 6 years.
“Future work should try and understand which kids are most vulnerable to ozone based on timing of exposure, genetic risk factors and co-exposure to other environmental chemical and non-chemical stressors,” Dearborn told Healio. “Recognizing that asthma is a heterogenous disease that may present differently in patients across the life course, investigating early-life ozone exposure on specific endotypes or phenotypes of asthma are important next steps.”
For more information:
Logan C. Dearborn, MPH, can be reached at dearbl@uw.edu.
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