Being overweight puts patients with asthma at a significantly higher risk of an exacerbation compared to non-obese patients especially in the colder months, say US researchers.
They analysed the data of 17,316 adult patients with persistent asthma- (80% overweight or obese) - and 10,700 children (46% overweight or obese).
The team found that the rate of exacerbations over a year increased linearly with BMI in both adults and children, and exacerbations were more common in the autumn and winter than the spring and summer.
Compared with normal-weight patients in the spring and summer, obese or overweight patients had a 62% increased risk for exacerbations in the autumn 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 autumn and winter than the spring and summer.
The authors say there is indirect evidence from other studies that low vitamin D status in overweight patients may make them susceptible to viral infections, especially in the colder months.
The study has just been published online in the Journal of Allergy and Clinical Immunology: In Practice.