The rate of asthma continues to steadily increase worldwide, but younger women may be particularly susceptible.

"Young women had the highest risk of developing asthma," says Lars Larsson, MD, PhD, associate professor of respiratory medicine at the University of Ostersund, Sweden. "We aren't sure why young women have higher rates of asthma. However, we do know they smoked more than the other groups."

Swedish researchers presented their study at the American Thoracic Society annual meeting.

"This is an important issue," says J. Randall Curtis, MD, international program chairman of the American Thoracic Society "This is the first study to identify young women as being at highest risk for adult-onset asthma."

While other studies have documented a rise in the number of asthma cases, this study clearly identifies young women as being at higher risk, he says.

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Asthma and Women

Swedish researchers surveyed more than 11,000 individuals in 1990. Participants of various ages were questioned about any respiratory symptoms. Thirteen years later, a second survey was taken of the same group, with 8,000 individuals responding.

Six percent of teenage girls surveyed back in 1990 had asthma. That number dramatically increased 13 years later when 17 percent of the same young women reported having asthma, Larsson says.

The next highest rate of asthma was found in young men. Initially 6 percent reported having asthma. More than a decade later, 14 percent had been diagnosed with asthma.

While the rates of asthma in middle-aged and older Swedes also increased, it was not as dramatic as in younger adults. The incidence of asthma in middle-aged adults increased from about 5 percent in the 1990 survey to 11 percent in the 2003 survey; the rates of asthma in the elderly increased from 6 percent to 10 percent.

The researchers concluded that young women have the highest risks of developing adult-onset asthma. Overall the rate of developing asthma was 8 percent in women and 6 percent in men, Larsson says.

Click here for Web MD's "How Serious Is Your Asthma? Rate Symptoms."

There were other risk factors for developing asthma that the researchers found:

If a family member had asthma, it increased a person's asthma risk threefold.
Younger-age individuals had twice the risk of developing asthma than older individuals.
Women had 1.2 times the risk of developing asthma than men.

"Being overweight and smoking were big risk factors," Larson says. Obesity placed individuals at 1.5 times the risk of developing asthma, and smoking posed a 1.2 times higher risk than nonsmoking.

Nineteen percent of women and 15 percent of men smoked, he says.

Larsson says he is unsure why young women were more apt to develop asthma than other Swedish adults, but smoking and weight may contribute to the high incidence.

Click here for Web MD's "Frequently Asked Questions About Asthma."

By Linda Little, reviewed by Brunilda Nazario, MD

SOURCES: American Thoracic Society 2005 International Conference, San Diego, May 20-25, 2005. Lars Larsson MD, PhD, associate professor of respiratory medicine, University of Ostersund, Sweden. J. Randall Curtis, MD, American Thoracic Society international program chairman.