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BackgroundChildhood asthma and obesity prevalence have increased in recent years suggesting a potential association. However, the direction of any association is poorly understood and the potential causal-relationship is unknown.MethodsWe examined the association between overweight/obesity, defined by body mass index (BMI) <18 years of age, and subsequent physician-diagnosed incident asthma at least one year after BMI assessment. We sought to explore potential effect modification by sex. PubMed and Embase were searched using keywords and restricted to subjects aged 0–18 years. There were no date or language restrictions. From each study we extracted: authors, publication date, location, overweight/obesity definitions, asthma definitions, number of participants, recruitment duration, description of cohort, follow-up time, adjusted effect estimates (with 95% CI) and estimates of subgroup analysis.ResultsSix prospective cohort studies which focused on children <18 years of age met criteria for inclusion. The combined risk ratio (RR) of overweight was associated with asthma (RR = 1.35; 95% CI = 1.15, 1.58). In boys, the combined RR of overweight on asthma was significant (RR = 1.41; 95% CI = 1.05, 1.88). For girls, when BMI was defined by Z-score, the combined RR of overweight on asthma was also significant (RR = 1.19; 95% CI = 1.06, 1.34). The combined risk ratio (RR) of obesity was associated with asthma in both boys and girls (RR = 1.50; 95% CI = 1.22, 1.83), in boys only (RR = 1.40; 95% CI = 1.01, 1.93) and in girls only (RR = 1.53; 95% CI = 1.09, 2.14).ConclusionsOverweight and, especially, obese children are at increased risk of subsequent physician diagnosed asthma in comparison to normal weight children. Except for sex, no studies reported any other potential effect modifiers. The observed sex effects were inconsistent.

Background: Lead can adversely affect child health across a wide range of exposure levels. We describe the distribution of blood lead levels (BLLs) in U.S. children ages 1–11 y by selected sociodemographic and housing characteristics over a 40-y period. Methods: Data from the National Health and Nutrition Examination Survey (NHANES) II (1976–1980), NHANES III (Phase 1: 1988–1991 and Phase II: 1991–1994), and Continuous NHANES (1999–2016) were used to describe the distribution of BLLs (in micrograms per deciliter; ) in U.S. children ages 1–11 y from 1976 to 2016. For all children with valid BLLs ( ), geometric mean (GM) BLLs [95% confidence intervals (CI)] and estimated prevalence (95% CI) were calculated overall and by selected characteristics, stratified by age group (1–5 y and 6–11 y). Results: The GM BLL in U.S. children ages 1–5 y declined from (95% CI: 14.3, 16.1) in 1976–1980 to (95% CI: 0.78, 0.88) in 2011–2016, representing a 94.5% decrease over time. For children ages 6–11 y, GM BLL declined from (95% CI: 11.9, 13.4) in 1976–1980 to (95% CI: 0.58, 0.63) in 2011–2016, representing a 95.3% decrease over time. Even so, for the most recent period (2011–2016), estimates indicate that approximately 385,775 children ages 1–11 y had BLLs greater than or equal to the CDC blood lead reference value of . Higher GM BLLs were associated with non-Hispanic Black race/ethnicity, lower family income-to-poverty-ratio, and older housing age. Discussion: Overall, BLLs in U.S. children ages 1–11 y have decreased substantially over the past 40 y. Despite these notable declines in population exposures to lead over time, higher GM BLLs are consistently associated with risk factors such as race/ethnicity, poverty, and housing age that can be used to target blood lead screening efforts. https://doi.org/10.1289/EHP7932