Significant differences in health characteristics may provide insight into why females are far more likely to suffer asthma than males
Significant differences in the characteristics of asthma sufferers can provide insight into why severe cases of the condition are more common in females than males, according to a new study by researchers from Italy.
Almost two-thirds of those in an Italian web-based registry of severe asthmatics age 12 and above were female, the study found. But there were several differences in the comparative health characteristics of the 1123 patients evaluated.
Late-onset asthma, obesity, and gastroesophageal reflux disease (GERD) were more common among females, according to the study published in Allergy, Asthma and Immunology Research. They also tended to have poorer asthma control and a higher number of severe flare-ups leading to hospitalization.
Males, on the other hand, were more likely to have previously smoked, to have nasal polyps, or to have biomarkers of type 2 inflammation: blood eosinophil, exhaled nitric oxide, and serum immunoglobulin E levels.
Comorbidities in females, such as obesity and GERD, are associated with inflammation unrelated to eosinophils, which may explain the differences in lab studies between the sexes, the authors said.
Asthma affects about 5% of the population worldwide, although the percentages vary widely among countries and continents, the researchers said. Asthma is more prevalent in boys at younger ages, but becomes more common in females after puberty, a sex disparity that disappears after females go through menopause.
There are number of reasons that could account for the differences between severe asthma sufferers of the 2 sexes, the study said. They include hormonal factors, environmental exposure, and type and rate of comorbidities. Also, research has pointed to the influence of hormones: ovarian hormones seem to increase bronchial inflammation, while testosterone seems to decrease it; estrogen fluctuations are believed to be connected; and hormone replacement therapy seems to increase asthma risk.
The Italian registry data showed that the onset of the condition was comparable between the sexes. However, intermediate onset (ages 12-40 years) and late onset (over age 40) were more common among females.
As for smoking, males with asthma were more likely to have given up the habit (76.2% vs 69.1%), while females were more likely than males (27.3% vs 20.4%) not to smoke at all. Around 3.5% of both sexes currently smoke.
The correlations between being overweight and having asthma worked in 2 directions. The number of overweight patients in the body mass index (BMI) range of 25 to 30 kg/m2 was larger for males, but obesity (BMI > 30) was greater among females. Most of the patients had a BMI above the normal range.
Although females tended to have worse control of their asthma, the average number of severe flare-ups (requiring oral corticosteroids for at least 3 days) and visits to the emergency department were similar among both sexes. However, females were slightly more likely to have been hospitalized in the previous year. Approximately 1 of 5 patients reported hospital stays overall.
Senna G, Latorre M, Bugiani M, et al; SANI Network. Sex differences in severe asthma: results from severe asthma network in Italy-SANI. Allergy Asthma Immunol Res. 2021;13(2):219-228. doi:10.4168/aair.2021.13.2.219