Dec 19, 2019 3:00 PM


Over the past three decades there has been a parallel rise in two of the most common health conditions in children — asthma and obesity — suggesting the two may be linked. After developing a new method to model health data, scientists at University of Utah Health and the University of Southern California have found a possible explanation for the connection: asthma leads to the onset of obesity. By understanding how one condition gives rise to the other, researchers may be able to devise strategies for preventing obesity in this subset of children.

A report of the research findings were published in the American Journal of Epidemiology.

Yue Zhang, PhD, lead author of the study and research associate professor of internal medicine at U of U Health, found the co-occurrence of asthma and obesity compelling but was puzzled by previous studies examining the issue. Some investigations suggested that asthma led to obesity but others pointed to the opposite. In evaluating the body of research, it dawned on him that something had been missing from their analyses.

In real-life, it’s not the case that one condition develops independently and then a second one arises, as models used previously seemed to imply. Rather, when someone has two health conditions there is likely a dynamic give and take between them. For instance, asthma may lead to obesity but then the latter may cause asthma to worsen.

“Since this model allows for a bi-directional relationship, we can simultaneously examine how conditions contribute to one another,” says Zhang.

To address this possibility, the researchers used a joint modeling approach to evaluate a dynamic relationship between the two conditions over time. They applied their model to data from children who took part in the California Children’s Health Study, the largest investigation examining the impact of air pollution on this population. The survey documented occurrence of asthma, height, weight and body mass index (BMI), and recorded proxies that estimated a child’s physical activity, medication use and other variations that could influence respiratory health and obesity.

Analyses of two datasets showed that children with diagnosed asthma had increased odds of becoming obese by the next annual visit compared to children without asthma. A cohort of 5,193 kindergarten-age children who were enrolled in the study in 2002-3 showed the odds of children with asthma becoming obese increased by 38% compared to children without asthma. Similar results were found after examining data from a second set of 3,498 children who were in the 4th grade at enrollment during 1992-3 and 1995-6. The odds of children with asthma becoming obese compared to those without in this second analysis increased by 42%.

“It is interesting that we found nearly identical results in examining the two cohorts,” says Zhang. “It gives us confidence in the reproducibility of our conclusion.”

There was no statistically significant evidence of the opposite, of obese children being diagnosed with asthma in their subsequent visit.

The mechanisms linking asthma to development of obesity remain unclear but could be attributed to medication use, decrease in physical activity, sleep disturbances, metabolic or inflammatory disorders, or a combination. Additional research will need to be done to determine whether the results from this study can be replicated in other populations and to identify key pathways that drive obesity onset in children with asthma. The ultimate goal is to develop prevention and adequate treatment of asthma to reduce the risk for future obesity.

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This work was supported by University of Utah Environmental Influences on Child Health Outcomes (ECHO); National Institutes of Health; National Institute of Environmental Health Sciences; the Southern California Environmental Health Sciences Center; Children’s Environmental Health Center; Environmental Protection Agency; Maternal and Developmental Risks from Environmental and Social Stressors (MADRES) Center; National Institute for Minority Health and Health Disparities and Environmental Protection Agency; Hastings Foundation.

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