The Asthma Gender Gap
Why adult asthma is more common – and often more severe – among women
By Laurie Ross
Heather Spears was a runner who followed a healthy lifestyle of eating and exercising. Ten years ago, at the age of 33, she developed a case of bronchitis that just wouldn’t go away. Her doctor diagnosed asthma.
“It was weird,” she recalls. “My family has allergies, but no history of asthma. I was a fairly active individual – I ran half-marathons and generally took good care of myself. Now I am really prone to infections and my asthma is very difficult to treat. My doctor says, ‘Just stay home and try not to get sick.’”
What Heather didn’t know was she had two significant risk factors for adult-onset asthma: She has multiple allergies and she is a woman.
The female risk factor may sound surprising, as most people think of asthma as a childhood disease that affects boys more than girls.
But somewhere in the teens and early 20s, the girl-to-boy ratio flips, and from puberty on, it’s a disease that affects women more often and more seriously than men.
What’s Going On: Is It Hormones?
“Gender differences in asthma prevalence and severity have been reported worldwide,” says Maeve O’Connor, MD, a board-certified allergist in Charlotte, North Carolina. “After puberty, asthma becomes about 40 percent more prevalent and severe in women, and women older than 15 are 2.3 times more likely than males to be admitted to the hospital for asthma.”
Studies to determine the exact effect of reproductive hormones on asthma are ongoing, but Dr. O’Connor says research indicates that estrogen may act directly on the immune system to increase the severity of asthma symptoms. It may also act indirectly to damage lung mechanics and increase inflammation.
Testosterone, on the other hand, has a positive effect on the immune system, according to a recent study at the Walter and Eliza Hall Institute of Medical Research in Melbourne, Australia.
“We discovered that testosterone quiets down a type of immune cell called innate lymphoid cells (ILC) so they are not as reactive to things that normally trigger asthma symptoms,” says Gabrielle Belz, professor of medical biology at the University of Melbourne and lead researcher on the study.
“We believe that the increase in testosterone in boys at puberty triggers their innate cells to be less reactive, resulting in a significant decrease in the incidence and severity of asthma.”
Estrogen Ups and Downs
Estrogen doesn’t seem to have a direct up-and-down effect on asthma, but rather it is the fluctuations in estrogen and progesterone hormones that cause problems: these fluctuations often occur during menstruation, pregnancy and menopause.
Many women find that their asthma symptoms correspond with their monthly cycles.
“Most hospitalizations for asthma in women occur right before a woman’s period begins,” says Dr. O’Connor. “Declining hormone levels may trigger an asthma flare, and symptoms can start to worsen anywhere from four days before menstruation through the last day of the menstrual cycle.”
Heather Spears noticed hormone-related effects on her asthma right away.
“I mentioned it to my doctor fairly early in my diagnosis,” she says. “Most of the time my asthma is set off by a specific allergen or irritant, but I’ve noticed that it’s far easier to be triggered during menstruation. Right around when my period would start, I’d have more asthma attacks and my peak flow would drop.”
Doctors encourage women with asthma to avoid their known allergens right before their period is about to begin. More can be done, however.
“Some women who have asthma symptoms right before or during their period can benefit from hormone therapy,” Dr. O’Connor says. “This may mean getting hormones via injection or a patch, or by birth control pills. In a recent study of menstruating women 28 to 58 years old, asthma symptoms improved for women taking oral contraceptives.”
Hormone therapy is not for everyone, however, as the link between asthma and hormonal drugs is unclear. Dr. O’Connor warns, “More studies are needed on the biological processes through which sex hormones might play a role in asthma and allergy.”
The uncertainty surrounding the pros and cons of hormone therapy is clearly seen during menopause, when many women take hormone replacement therapy (HRT) to stabilize their estrogen levels and prevent unpleasant symptoms.
Studies have shown conflicting results:
• Women with asthma who begin hormonal replacement therapy as they enter menopause may find their asthma improves.
• Women with no history of asthma who take HRT may be at increased risk of developing new asthma – which is often severe and difficult to treat.
“Postmenopausal hormone replacement therapy seems to increase the risk of severe asthma causing hospitalization,” says Dr. O’Connor. “If a woman on HRT shows severe asthma flares, it might be smart to stop.”
Elderly asthma patients of either sex are more likely to go underdiagnosed and undertreated than younger patients – putting them at higher risk of complications and death.
The changes in the aging immune system are complex and not fully understood, but the underlying airway inflammation of asthma in this age group is likely different from younger patients and may be less responsive to traditional medications.
At highest risk of asthma death are women over the age of 65: They face an asthma death rate nearly four times higher than in other groups.
But hormones aren’t the only factor explaining why women have more asthma and more hospitalizations for asthma than men. “The impact of sex hormones is difficult to differentiate from the effects of age, obesity, allergy, and other gender-related environmental exposures,” says Dr. O’Connor.
Some factors involved:
• Lung size: Female lungs are often smaller and airways narrower than in males of similar age and size.
• Environmental exposure to allergens: Women may have more exposure to dust mites, mold or pets in the home or in certain occupations like cleaning.
• Menopause: With the onset of menopause, some women experience an increase in allergies and allergic asthma. Others may become allergic to something that never bothered them before.
• Weight gain: Older women are more at risk for obesity than men, which can affect asthma severity.
• Healthcare habits: Women may pay more attention to their symptoms and seek medical attention more readily than men, which would contribute to increased healthcare costs and statistics.
• Caregiving: Many women serve as the primary caregiver in their family and this role might hamper self-care.
In addition, middle-aged women who take inhaled or oral corticosteroids long-term for asthma may experience side effects that are mistaken for menopause. Side effects can include osteoporosis, a bone-weakening disease, as well as eye problems such as glaucoma and cataracts. If these symptoms occur with corticosteroid use, talk with your doctor.
At any age and gender, asthma is a complex disease that affects each person differently – and generalizations play only a small part in reaching a diagnosis. Treatment for most cases of asthma remains consistent (depending on the level of severity): a quick-relief inhaler to treat flares and a daily maintenance medication – such as an inhaled corticosteroid – to prevent symptoms.
Understanding gender differences is important to provide effective education and personalized management plans.
What to Expect When You’re Pregnant
Pregnant women with asthma may – or may not – find their symptoms change during pregnancy. At least one study showed 1/3 of women found their asthma got worse, 1/3 got better, and 1/3 stayed the same.
No matter where you fall on that spectrum, it’s important to remember that healthy breathing is vital to a healthy pregnancy. Your unborn baby depends on you for a constant supply of fresh air. Asthma symptoms such as coughing, wheezing or shortness of breath are signs your baby’s air supply may be affected.
That’s why it’s essential to see a board-certified allergist or pulmonologist in addition to an obstetrician, and develop a written management plan that fits your personal asthma patterns, lifestyle and pregnancy.
Take extra precautions to avoid exposure to allergens, irritants and infections that set off your asthma, and use medications wisely to prevent symptoms. Many asthma medications are judged safe to use during pregnancy, but some may have to be adjusted.
Reviewed by William Berger, MD, Eileen Censullo, RRT and Andrea Jensen, CHES, AE-C