Women with extra fat around their waists are more likely to develop asthma, even if they aren't overweight, a new study finds.
The California Teachers Study of more than 88,000 women found the same association between obesity and increased incidence of asthma that has been seen in other research, according to the report in the journal Thorax.
However, it also found an increased incidence of asthma among women with a larger waist size, even if they were of normal weight.
Using the standard designations of obese" for a woman with a body mass index (BMD) of 30 or higher and extremely obese" for a body mass index (BMD) of 40 or higher, the study found a doubled incidence of asthma among the obese women and a more than tripled incidence among the extremely obese.
The study also uncovered a 37% increased incidence of asthma among women with a waist circumference of 88 centimeters-about 35 inches-even if they were not overweight.
Other studies have documented the overall association between obesity and asthma, said Alejandro Arroliga, MD, a pulmonologist and chairman of medicine at the Scott & White Memorial Hospital and Clinic in Temple, Texas, "This is one of the biggest, with more than 88,000 women. It's huge," he said.
While the study was not designed to determine why the location of body fat could play a role in development of asthma, "waist size can be an indicator of the type of body fat," explained study author Julie Von Behren, MPH, a research associate at the Northern California Cancer Center. "Abdominal fat is visceral fat, which is more biologically active. It has been linked to diabetes and heart disease."
Fat around the waist "could be acting in some inflammatory way," she said.
That is a plausible, though unproven, explanation, said Dr. Arroliga. "We know that obesity can cause an inflammatory state," Dr. Arroliga said. "Markers of inflammation are increased in obesity."
While one conventional explanation is that body fat puts a squeeze on airways, some previous studies have pointed toward the composition of body fat as a possible element in asthma risk, he said.
"But it is still unclear why there is this association," Dr. Arroliga said. "The biological explanation lags behind the epidemiological evidence."
Whatever the reason, the association with asthma provides another reason not to put on extra weight, Von Behren said.
Asthma Patients Neglect Flu Shots
People with asthma are at higher risk for influenza complications, such as pneumonia, than people without asthma, according to a recent study.
In a survey of 173,000 adults, researchers found that only 33.9% of asthma patients ages 18 to 49 and 54.7% of asthma patients ages 50 to 64 got annual influenza vaccinations (compared with 28.8% of adults ages 18 to 64 without asthma).
If you have asthma: Regardless of your age, get all flu vaccinations-including the new HINI vaccine-recommended by your doctor.