Interaction between sex and age in the prevalence of current asthma

Abstract

Rationale It is generally reported that asthma is more prevalent in females than males. This fact, along with findings from basic research in our laboratories, suggests that airway hyperresponsiveness may be influenced by sex hormones. This observational study compared the prevalence of current asthma between males and females before puberty and during the reproductive and post-reproductive years. Methods Data were obtained from the third National Health and Nutrition Examination Survey. Current asthma was assessed by questionnaire. Adjusted odds ratios (OR) comparing males and females were estimated for various age categories. Smoothed curves showing the prevalence of current asthma by sex and age were constructed. Results Over all ages, the prevalence of current asthma was higher in females than males (5.9% vs. 5.0%, P=0.04). Smoothed curves indicated that the prevalence of current asthma increased steadily from birth to the early teenage years in both sexes, but the prevalence was significantly higher in males (OR males vs. females, ages 1-14 years=1.4, 95% CI=1.1-1.8). From the teenage years through midlife, the prevalence decreased dramatically in males and increased in females (OR females vs. males, ages 15-54 years=1.6, 1.2-2.1). From midlife, the prevalence increased in males and decreased in females, converging in late adulthood (OR females vs. males, ages 55-90 years=0.9, 0.7-1.3). Conclusions With respect to current asthma, there is a strong interaction between sex and age, perhaps due to the influence of sex hormones. Other explanations and implications for clinical practice and research will be discussed.