Which comes first: obesity or asthma?

After years of knowing that obesity and asthma had some connection, but not whether obesity brought about asthma or vice versa, new evidence may finally hold the answer.

Guidelines: The asthma reference guide for the Pediatrician

Approximately 12.5 million US children aged 2 to 9 years are classified as obese, according to the National Health and Nutrition Examination Survey 2007-2008, and children with obesity are at increased risk of developing asthma. Childhood asthma is the primary reason for school absences in the United States, accounting for more than 14 million missed school days each year.

In a recent article published in the Annals of Allergy, Asthma, and Immunology, researchers from Massachusetts General Hospital, Harvard Medical School, and Boston Children’s Hospital note that the connection between obesity and asthma is likely to be multifactorial, with the beginnings in utero and in early childhood. One of the studies they reviewed found that fatty acid dietary supplementation during pregnancy does not lower the incidence of asthma. Another study showed that rapid growth in body mass index (BMI) in the first 2 years of life increased the risk of asthma up to 6 years of age. In yet another study, low birth weight was associated with asthma, and excessive BMI increased the risk.

The Childhood Asthma Management Program found a significantly decreased ratio of forced expiration volume in 1 second to forced vital capacity in children who were at or above the 85th BMI percentile when compared with children of a healthy weight. Other research found overestimation of poor asthma control in obese pediatric asthma patients because of perceived dyspnea owed to altered properties of the chest wall. More lung volume assessments in childhood obesity study were recommended because of conflicting data.

Airway hyperresponsiveness (AHR) data in pediatric asthma patients who are obese is inconclusive. One study found no significant difference in AHR between obese and healthy-weight children after an exercise challenge. However another study showed that weight loss in obese children decreased the severity of exercise-induced bronchoconstriction.

Lead researcher Perdita Permaul, MD, said that although there is not as much data for the association between obesity and asthma in children as there is for adults, it seems likely that obesity leads to the onset of asthma, similar to the relationship between asthma and obesity in adult patients.

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