These clinical studies are subject to a variety of important biases. They deal with a small number of selected cases, often poorly defined. They often are confounded by effects of treatment. No study adjusts for baseline level of FEV,, and no study uses multivariate techniques to assess the relationship of bronchial responsiveness to disease severity. Most important, the within-person variability of bronchial responsiveness is poorly understood, and estimates of within-person variability and how it relates to the presence or absence of symptoms are lacking. flovent inhaler
Gender differences in asthma prevalence are clear: males are more likely than females to have asthma in early childhood, and females are more likely than males to have asthma after age 10. This increased female prevalence of asthma is associated with an increase in asthma mortality, which would be 1 index of disease severity. These gender differences in asthma prevalence, however, may reflect diagnostic bias on the part of physicians. When one looks at airway responsiveness by gender, results from population-based studies give equivocal results (Table 4). Weiss et al studied 134 adults, aged 25 to 47 years, using eucapneic hypernea to subfreezing air. A decrease in FEV/FVC of 9% or more was considered a positive test. The frequency of response in females (7%) appeared to be equal to that in males (6%).

Table 4—Population Studies on Gender Differences in Airway Responsiveness

Population Test Criteria Prevalence (%) Male Female
US random population FEV/FVC > 9% 6 7
(age 25-47) cold air
Australia random population PD*, FEV, < 3.9 m 8.9 13.7
(mean age, 49) histamine
Netherlands random PDa, FEV, < 126 22
population sample 16 mg/m
(ages 14-64) histamine