Prevalence of asthma among adult females and males in the United States: results from the National Health and Nutrition Examination Survey (NHANES), 2001-2004.

Background: The prevalence of asthma has increased over the last three decades with females exhibiting a higher prevalence of asthma than males. The objective of this study was to obtain gender-specific estimates of the prevalence of current and ever asthma and describe the relationships between risk factors and asthma by gender in US men and women ages 20 to 85.

Methods: Data for this study came from two cycles (2001-2002 and 2003-2004) of National Health and Nutrition Examination Survey (NHANES) and included 9,243 eligible adults: 4,589 females and 4,654 males. Multiple logistic regression was used to investigate gender-specific associations between race/ethnicity, body mass index (BMI), sociodemographic characteristics, and smoking habits for current asthma and ever asthma.

Results: The prevalence of current asthma was 8.8% for women and 5.8% for men, while the prevalence of ever having been diagnosed with asthma was higher (13.7% and 10.4% for women and men, respectively). Current asthma was less prevalent in Mexican American women (1.9%) and men (0.9%) born in Mexico as compared to Mexican Americans born in the U.S. (8.7% and 5.2% for women and men, respectively) or for any other ethnic group. Approximately 20% of extremely obese women and men had ever been diagnosed with asthma; among this group, 15% reported they had current asthma. Results from multiple logistic regression models indicate that extreme obesity and living in poverty were strongly associated with current and ever asthma for both women and men, as was former smoking and ever asthma for men.

Conclusion: As compared to previous NHANES reports, our results indicate that the prevalence of asthma among U.S. adults continues to increase. Further, our findings of marked differences among subgroups of the population suggest asthma-related disparities for impoverished persons and greater prevalence of asthma among obese and extremely obese US adults.