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03-10-2013 | Respiratory | Article

Obese asthma patients at risk for seasonal exacerbations


Free abstract

medwireNews: Research shows that overweight and obese patients with asthma have an increased risk for exacerbations, particularly in the fall and winter.

Study authors Michael Schatz (Kaiser Permanente Medical Center, San Diego, California, USA) and colleagues say the findings hint toward a role for vitamin D status in the association between body mass index (BMI) and asthma exacerbations over other mechanisms like corticosteroid resistance.

They analyzed the data of 17,316 adult patients (80% overweight or obese) and 10,700 children (46% overweight or obese) with persistent asthma.

The team found that the rate of exacerbations during a single year increased linearly with BMI in both adults and children, and exacerbations were more common in the fall and winter than the spring and summer.

And, after adjusting for confounders including gender and education level, there was a significant relationship between BMI and the risk for exacerbations in the fall and winter in adults and children.

Furthermore, in adults there was significant interaction between BMI status and season, showing that overweight and obese patients were particularly at risk for fall and winter exacerbations. Compared with normal-weight patients in the spring and summer, these patients had a 62% increased risk for exacerbations in the fall and winter, but were only 16% more likely to have an exacerbation in the spring and summer.

Normal-weight patients were also affected by the season but to a lesser degree, being just 19% more likely to have an exacerbation in the fall and winter than the spring and summer.

Writing in the Journal of Allergy & Clinical Immunology In Practice, Schatz and team say that the findings may help shed light on the mechanism by which obese patients with asthma are at greater risk for exacerbations, supporting a role for vitamin D insufficiency, which could be, in turn, related to the risk for viral infections.

“One would not expect corticosteroid resistance to vary as much by season, so we believe that the results of the current study are less likely to be explained by this mechanism,” they comment.

However, as BMI was also related to exacerbation risk, independent of season, they say it is still possible that corticosteroid responsiveness may play a role that potentially becomes amplified during the fall and winter months.

“Indirect evidence from other studies supports low vitamin D status in patients with a higher BMI value as a mechanism for some of the season-specific observations, but confirmation by randomized controlled trials of vitamin D supplementation will be necessary to test this hypothesis and define its clinical importance,” the authors conclude.

medwireNews ( is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2013

By Kirsty Oswald, medwireNews Reporter