TORONTO (Reuters Health) - Obese women have almost double the risk of developing asthma compared with women who are not obese, Canadian researchers reported here at the 2001 Congress of Epidemiology. However, the link between obesity and asthma risk did not apply to men in the study.

Dr. Yue Chen, a professor of epidemiology at the University of Ottawa, and colleagues tracked new cases of asthma among 4,266 men and 4,883 women over a 2-year period. During the study, 1.6% of the men and 2.9% of the women developed asthma.

"Average changes in body weight and body mass index over the 2-year period of observation were relatively small and were not associated with the incidence of asthma", the researchers observed.

Body mass index (BMI) is a measure of weight relative to height that is used to determine whether a person is overweight or obese. People with a BMI above 25 are considered overweight, while those with a BMI above 30 are considered obese.

Chen told Reuters Health in an interview that independent of age, women with a BMI of at least 30 were about twice as likely to develop asthma as women with a normal BMI.

In contrast, obese men were not significantly more likely to develop asthma than normal-weight men.

Chen said the data are "consistent'' with previously reported data in which obesity was associated with a higher risk of asthma in Canadian women, though not in men.

"We still need more studies, but other studies have consistently shown that BMI is related to the new incidence of asthma in women, too", Chen said.

Whether there is an interaction between genetic predisposition to asthma, which accounts for approximately 40% of asthma, and obesity, is still unknown, he added.