Early intervention and child physical health: Evidence from a Dublin-based randomized controlled trial

•There is a steep socioeconomic gradient in children's early health conditions.•This randomized controlled trial tests the causal impact of early intervention on physical health.•The intervention reduces wheezing/asthma by 15.5 percentage points.•The intervention has a greater effect on boys than girls.•Home visiting programs may be effective strategy for reducing health inequalities.

This article investigates the impact of an early intervention program, which experimentally modifies the parenting and home environment of disadvantaged families, on child physical health in the first 3 years of life. We recruited and randomized 233 (115 intervention, 118 control) pregnant women from a socioeconomically disadvantaged community in Dublin, Ireland into an intervention or control group. The treatment includes regular home visits commencing antenatally and an additional parenting course commencing at 2 years. Maternal reports of child health are assessed at 6, 12, 18, 24, and 36 months. Treatment effects are estimated using permutation testing to account for small sample size, inverse probability weighting to account for differential attrition, and both the stepdown procedure and an indices approach to account for multiple hypothesis testing. Following adjustment for multiple testing and attrition, we observe a positive and statistically significant main treatment effect for wheezing/asthma. The intervention group are 15.5 percentage points (pp) less likely to require medical attention for wheezing/asthma compared to the control group. Subgroup analysis reveals more statistically significant adjusted treatment effects for boys than girls regarding fewer health problems (d = 0.63), accidents (23.9 pp), and chest infections (22.8-37.9 pp). Our results suggest that a community-based home visiting program may have favorable impacts on early health conditions.