MONDAY, May 12, 2025 (HealthDay News) -- Young women taking the Pill might have an increased risk of asthma attacks, a new study says.
Taking the progesterone-only form of the contraceptive pill can increase asthma attacks among women under 35, researchers reported May 7 in ERJ Open Research.
There was no similar risk among women taking the combo estrogen/progesterone pill, researchers found.
“Asthma is common in women, and unfortunately, women are twice as likely to die from asthma as men,” Dr. Chloe Bloom, a clinical senior lecturer in respiratory epidemiology at Imperial College London in the U.K., said in a news release. “To help prevent these deaths, we need a better understanding of why women are at greater risk.”
For the study, researchers studied data on nearly 262,000 U.K. women 18 to 50 diagnosed with asthma.
The team compared women who’d never used the pill with women who started taking either version of the pill, seeing which of them experienced asthma attacks between 2004 and 2020.
Women under 35 taking the progesterone-only pill had a 39% higher risk of asthma attacks, results show.
“We found that the combined pill did not affect whether women had asthma attacks, but some women who took the progesterone-only pill had more asthma attacks,” Bloom said.
“These included women under 35 years old, those who used fewer asthma medications, like inhaled or oral steroids, and those with higher levels of inflammation linked to asthma in their blood,” she said.
Those relying on fewer asthma medications had a 20% higher risk of asthma attacks with the progesterone-only pill.
Researchers also found a 24% higher risk among women with eosinophilic asthma, in which sufferers have high levels of blood cells called eosinophils that cause inflammation.
“Asthma is common in women of reproductive age, many of whom are taking the pill,” Bloom said. “This study helps women and healthcare professionals make more informed decisions about which contraceptive pill might be best for them. The findings also add another piece to the puzzle of why women may be more likely to have severe asthma than men.”
Researchers said excessive progesterone could contribute to increased inflammation in women’s airways. Women who use the progesterone-only pill might also have some as-yet-unidentified unique characteristics that make them more vulnerable to asthma.
The researchers continue to study the effects of sex hormones on asthma, turning their attention to the possible effects of pregnancy or hormone replacement therapy.
The new study is an important step toward figuring out women’s vulnerability for asthma, said Apostolos Bossios, an associate professor of respiratory medicine at Karolinska University Hospital in Stockholm. He heads a European Respiratory Society group on airway diseases, asthma and chronic cough.
“Women with asthma who are taking the … pill, or considering it, should speak to their doctor about their contraception options and their asthma symptoms,” said Bossios, who was not involved in the research. “Whichever contraception they use, it’s vital that women with asthma use their preventer inhalers and any other prescribed treatments regularly.”
More information
Planned Parenthood has more on the birth control pill.
SOURCE: European Respiratory Society, news release, May 7, 2025
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