Impact of adolescence and gender on asthma hospitalization: a population-based birth cohort study.

Our objective was to determine the impact of gender and age on asthma hospitalization rates among children. We used a population-based retrospective birth cohort study to determine yearly age- and gender-specific asthma hospitalization rates between ages 2-18 years in a cohort of all children born in Washington State between 1980-1985. In addition, we assessed factors associated with the hospitalization of a given child for asthma both before and during adolescence, and factors associated with an initial asthma hospitalization during adolescence. Outcome measures included age- and gender-specific rates of hospitalization for asthma, diabetes, seizures/epilepsy, and nonasthma respiratory diagnoses. Asthma hospitalization rates for boys were significantly higher than for girls between ages 2-12 years, the gender gap in asthma hospitalizations reversed between ages 13-14 years, and rates for girls were significantly higher than boys between 16-18 years of age. The male peak asthma hospitalization rate per 100,000 cohort members occurred at age 4 years (12.7; 95% confidence interval (CI), 11.1-14.3), and the male trough rate occurred at age 18 years (4.1; 95% CI, 2.8-5.4), whereas the female peak asthma hospitalization rate occurred at age 17 years (9.4; 95% CI, 7.8-11) and the female trough rate at age 2 years (5.2; 95% CI, 4.2-6.2). Age-specific hospitalization rates for diabetes mellitus and epilepsy were similar for boys and girls throughout childhood. Female gender was strongly associated with asthma hospitalization occurring in an individual child both prior to and during adolescence (rate ratio (RR), 2.0; 95% CI, 1.4-2.9), and was modestly associated with initial hospitalization in adolescence (RR, 1.15; 95% CI, 1.0-1.3). In conclusion, asthma hospitalization rates for boys and girls exhibit strikingly different patterns during adolescence. Potential explanations for these gender differences include hormonal changes during puberty, or gender-specific differences in environmental exposures such as diet, obesity, allergen exposure, or cigarette smoking.