By Joene Hendry

NEW YORK, US - Being overweight, especially around the middle, may increase a woman's risk for developing asthma, study findings hint.

In the study women who were overweight or obese were much more apt to have asthma than women at a healthy weight, public health researcher Julie Von Behren, of Northern California Cancer Center in Berkeley, and colleagues found.

And regardless of a woman's weight, a large waist size -- more than 88 centimeters or 34 inches -- also conferred increased risk for asthma, Von Behren and colleagues report in the medical journal Thorax.

Moreover, "obesity may make asthma symptoms more severe," Von Behren noted in an email correspondence to Reuters Health. Among the 88,304 women in the study, those who were obese "were more likely to report urgent medical visits and hospital admission due to asthma," Von Behren said.

She and colleagues used information from the California Teachers Study to compare current and retired female teachers' self-reported 18-year old height and weight, and their later self-measured waist size.

At the second measurement, the women ranged in age from younger than 40 to 70 years and older.

Overall, roughly 13 percent of the women were obese, having a body mass index (BMI) of 30 or more, and another 1.5 percent were extremely obese, having a BMI of 40 or more.

BMI is a standard measure used to gauge how fat or thin a person is. A normal BMI is between 18.5 and 24.9.

All levels of obesity, the researchers report, were strongly associated with having asthma.

"Even being modestly overweight was associated with higher asthma prevalence in this population," they note.

In addition, a large waist size was associated with modestly increased asthma prevalence among women who were at a normal weight.

"These findings are particularly troubling," Von Behren and colleagues say, given that the majority of American adults are now overweight or obese.