Effect modification of the intervention by child age on AM prevalence during follow-up of children enrolled in the longitudinal study (n = 10,282 child visits in the comparison arm and n = 10,236 in the intervention arm).
The blue dashed line represents fitted values obtained from the regression model for the intervention arm. The orange solid line represents fitted values obtained from the same regression model but for the comparison arm. Gray areas represent 95% confidence bands of kernel-weighted local polynomial smoothed values by study arm using the observed data. Mixed-effects regression models with restricted cubic splines (knots at 9, 12, and 16 months of child age) were used with health center catchment area and child as random intercepts and health district, sampling strata, month of inclusion, child sex, whether the child was a first live birth or not, age splines, and intervention as fixed effects. A chunk Wald test was used to test the “age spline × intervention” interaction terms (p-value shown). AM, acute malnutrition.