Rationale: Age and sex are associated with differences in asthma prevalence and morbidity.
Objectives: To determine if age and sex associate with distinct phenotypes and a variable response to therapy in subjects with mild to moderate asthma.
Methods: We used Asthma Clinical Research Network data to determine the impact of age and sex on phenotypes and treatment failures among subjects participating in 10 trials from 1993 to 2003.
Measurements and main results: A total of 1,200 subjects were identified (median age, 30.4 yr; male, 520 [43.3%]; female, 680 [56.7%]) and analyzed. A higher proportion of subjects greater than or equal to 30 years old experienced treatment failures (17.3% vs. 10.3%; odds ratio [OR], 1.82; confidence interval [CI], 1.30-2.54; P < 0.001), and rates increased proportionally with increasing age older than 30 across the cohort (OR per yr, 1.02 [CI, 1.01-1.04]; OR per 5 yr, 1.13 [CI, 1.04-1.22]; P < 0.001). Lower lung function and longer duration of asthma were associated with a higher risk of treatment failures. A higher proportion of subjects greater than or equal to 30 years old receiving controller therapy experienced treatment failures. When stratified by specific therapy, treatment failures increased consistently for every year older than age 30 in subjects on inhaled corticosteroids (OR per year, 1.03; CI, 1.01-1.07). Females had a slightly higher FEV1 % predicted (84.5% vs. 81.1%; P < 0.001) but similar asthma control measures. There was not a statistically significant difference in treatment failures between females and males (15.2% vs. 11.7%; P = 0.088).
Conclusions: Older age is associated with an increased risk of treatment failure, particularly in subjects taking inhaled corticosteroids. There was no significant difference in treatment failures between sexes.
Keywords: age; asthma; inhaled corticosteroid; sex; treatment failure.