Women and Asthma Through the Gender Lens (Women's Health Matters article) (Web resource; WHM resource) Author: Patricia Nicholson Organization: Women's College Hospital, Women's Health Matters When it comes to differences between men and women, lungs may not be the first thing that comes to mind. But more and more research is highlighting how men and women are affected differently by conditions such as lung cancer, chronic obstructive pulmonary disease (COPD) and asthma. In a presentation about gender and asthma at the 2009 Canadian Respiratory Conference in Toronto, Dr. Anna Day, director of the Gender and Airways Program at Women’s College Hospital in Toronto, explained why men may breathe a little easier than women when it comes to asthma. Asthma affects boys and girls differently in childhood, and men and women differently in adulthood, Dr. Day said. In children, asthma affects almost twice as many boys as girls, with about 18 per cent of boys reporting asthma compared to about 10 per cent of girls. However, by the time they reach adulthood, the prevalence of asthma in males drops to about 7.5 per cent because many boys outgrow their childhood asthma. In women, the prevalence in adults remains at about 10 per cent, but Dr. Day pointed out that it does not affect the same 10 per cent of females as childhood asthma. ‘If you look at the natural history of asthma you find that not only is pediatric asthma more common in boys than girls, not only do boys seem to outgrow their asthma, but the onset of asthma for many women is following puberty,’ Dr. Day said, adding that there are significant gender variations in the effects of asthma, and these change at puberty. ‘For our youngsters we find that boys are hospitalized twice as often now as girls for asthma. However something happens over the adolescent years and by the time we hit the 20s, or the second half or adolescence, we find that there are more women than men that are being hospitalized for asthma.’ Looking through the gender lens These differences suggest that asthma may have a different natural history for women than for men, Dr. Day said. Which prompts the question: is this biology or sociology? Using data from the Asthma in Canada survey, Dr. Day and her colleagues performed a ‘gender lens’ analysis of asthma symptoms, control, doctor visits, outcomes and patient knowledge. They found that while men and women tended to have the same number of asthma-related issues – such as waking up at night, experiencing daytime symptoms, limited physical activity – the specific symptoms they reported were different. Women were more likely to report symptoms suggesting poorer outcomes, such as limitations on physical activity, absenteeism and exacerbation of their condition. ‘Then we looked at other information such as the use of asthma medications, and we found that women were more likely to report using inhaled corticosteroids. Or, put another way, men were less likely to report using inhaled corticosteroids, which are considered the basic therapy for asthma,’ Dr. Day said. In fact, women were significantly better than men at looking after their asthma: women knew more about asthma, they knew more about their medications, they were optimistic about the outcome for their asthma and went to the doctor more often than men. However, they also had more unscheduled doctor visits (indicating the need for urgent care). ‘We found that women were more knowledgeable, visited their physicians more often, were more likely to be on anti-inflammatory medications, and yet they were having poorer outcomes,’ Dr. Day said. ‘We were very, very surprised. And we had to ask ourselves, perhaps there is a difference in biology.’ Size matters Recent research suggests that increased airway responsiveness – the hallmark of asthma – may be more prevalent in women than men. However this, too, changes at puberty, Dr. Day said: airway responsiveness is very similar in boys and girls until about age 10. After that age, responsiveness improves in boys, but stays the same in girls. There are several possible factors involved in the greater prevalence of airway hyper-responsiveness in women in adulthood: physiological differences in men and women, immunology, hormonal factors and genetic determinants. Physically, female lungs are smaller than male lungs. However, the airways within the lungs also differ. ‘Female children have larger airways in relation to lung size than males. In other words, the airways of boys are smaller in relation to their lungs than those of girls. You can see why if you get a viral infection and you have a smaller airway you’re more likely to wheeze,’ Dr. Day explained. At puberty, female airways grow in proportion to their lungs. But in males, airways grow larger in proportion to their lung size. ‘So by adulthood, the airways of men are about 17 per cent larger in diameter than the airways of women,’ she said. ‘So we do have tremendous changes in airway size in relation to lung size that may determine why we have differences to some extent in the genders between childhood and adult years. But that’s not the entire story.’ Reactions and receptors Immunology also differs by gender, which affects what will trigger the airway inflammation response that defines asthma. In childhood, boys have more allergic hypersensitivity in skin-prick tests than girls. But after puberty, women are more reactive on these tests. ‘There are tremendous gender differences in how the genders handle inflammation. We know that women are much more prone to inflammatory disease,’ Dr. Day said. Hormones also play a role in susceptibility. Research has shown that women are more likely to arrive at an emergency room for asthma treatment just before or during their period – when progesterone and estrogen levels fall. ‘We know that there is premenstrual activation of asthma in up to 40 per cent of women when you start looking for that,’ Dr. Day said. Hormone levels can also affect the receptor cells in the lining of the airways that stimulate the airways to relax or contract. Genetic factors governing those same receptor cells may predict whether a child will outgrow asthma. However, research suggests that a specific genetic factor in a boy indicates that his asthma will continue into his adolescence, but the same factor in a girl appears to have no effect. This suggests that genetic differences are modified by other processes. ‘Ultimately this gets us into the whole area of gender and pharmacology,’ Dr. Day said. There is some research suggesting that women do not respond to steroids as well as men, and this may be part of the reason that women tend to be hospitalized for asthma for longer periods than men. Asthma is not the only lung disease that affects men and women differently. Women who smoke are 50 per cent more likely than men to get lung cancer, and COPD has been increasing in prevalence among women in recent decades. ‘There are significant differences in airway disease when we take gender into account, and the differences are likely based on both physiology and psychosocial factors,’ Dr. Day said. ‘We need to understand these differences in risk and natural history when identifying, diagnosing and managing patients with airway disease if we want to impact on morbidity and mortality for pulmonary conditions.’ Version française :  Cliquez ici pour voir la description en français Purpose:  Consumer information/support; Health information Information Source:  Hospital/Clinic Geographic Origin:  Canada Language of Resource:  English Groups:  Adult women; Middle-aged women; Older women; Teenagers; Young women Last Reviewed by Women's Health Matters:  May 13, 2009