A new report confirms that women who are overweight run an increased risk of developing asthma and allergy, but men don’t.

Previous reports have linked asthma and obesity in women, but it was unclear if this association resulted from confusion between “real” asthma and breathing symptoms caused by being overweight. Also, it hasn’t been clear if the same pattern applied to men.

To investigate, Dr. Robert J. Hancox, from the University of Otago in Dunedin, New Zealand, and colleagues analyzed data from a group about 1000 subjects born in the same year.

Data on airway function and allergies was obtained for all the participants between 9 and 26 years of age, according to a report in the American Journal of Respiratory and Critical Care Medicine.

For females, their body mass index (BMI) - that is, weight in relation to height - was directly related to their risk of developing asthma or wheeze, needing asthma treatment, having allergies, and poorer lung function.

There was little evidence that BMI was associated with asthma or allergies in men, the investigators report.

The researchers estimate that “28 percent of asthma developing in women after age 9 is due to overweight.”

Why BMI is more often linked to asthma in females is unknown, “but may be partially explained by the fact that for a given BMI, women had a greater percentage of body fat than men,” Hancox said in a statement. This suggests that hormones might be involved in susceptibility to asthma.

SOURCE: American Journal of Respiratory and Critical Care Medicine, March 2005.