Age of Emergence of Disparities in Asthma Prevalence and Morbidity among U.S. Children.

Rationale: Early-life exposures may precipitate asthma, but their contribution to disparities in asthma is less clear. Objective: To elucidate racial, ethnic, and socioeconomic status (SES) disparities in the age trajectory of asthma burden among U.S. children. Methods: We analyzed three datasets: 1) 2016-2021 National Children's Health Survey (n = 223,551), 2) 2015-2017 Child Asthma Call-Back Survey (n = 4,289), and 3) 2018-2019 National Inpatient Sample (n = 23,713 children with asthma). We examined cumulative asthma prevalence by individual year of age and children's race and ethnicity or SES (National Children's Health Survey); mean age at asthma diagnosis by race and ethnicity and SES, unadjusted and adjusted for confounders (Asthma Call-Back Survey); and asthma hospitalization rates overall and per child with asthma by individual year of age and race and ethnicity (National Inpatient Sample). Results: Among White children, cumulative asthma prevalence increases gradually through childhood to 6.6% at age 5 years and 16.1% by age 17 years. Prevalence increases more sharply in early childhood among Black children, reaching 17.6% at age 5 years (risk ratio, 2.6; 95% confidence interval, 1.9-3.8), but plateaus after age 9 years, with a consequent decrease in Black-White relative disparities into adolescence. Disparities according to SES follow a similar trajectory, emerging early and subsequently narrowing. Similarly, Black, Hispanic, and low-income children with asthma are diagnosed at an earlier age than White (or high-income) children. The asthma hospitalization rate increases in the first years of life among all children, but most rapidly among Black children, with a peak absolute Black-White gap at age 4 years; the relative gap remains wide throughout childhood and peaks at age 10 years. However, per child with asthma, relative White-Black disparities in hospitalizations increase through age 15 years. Conclusions: Disparities in asthma prevalence emerge in early childhood and then narrow, suggesting that reducing early-life adverse environmental exposures may be key to asthma prevention. Policies to improve the social determinants of health during gestation and childhood, e.g., environmental equity and family income support, are needed.