Discussion
depression, cognitive and social emotional development, trauma
We found evidence of significant differences in child development between the richest and poorest population in Vietnam at both early and middle childhood. The wealth disparity in cognitive development was apparent as early as 1 year of age, maintained at 2y and increased remarkably at 6-7y, whereas the gap in social emotional development did not change over time. Our findings also clearly demonstrated that the quality of the home environment, maternal factors, and child HAZ significantly mitigated the disparities in cognitive development at early childhood and contributed to a small reduction of the gap at middle childhood. Most notably, the quality of the home environment played a key role in reducing the wealth gap in about 43% of cognitive development at 1y, and 50% of prosocial behavior score at 6-7y. The absence of any impact of the preconception intervention on the wealth gap, implied that there was neither evidence of a reinforcing interaction with wealth over time nor one that diminished such gaps. Thus, the intervention appeared neutral with respect to wealth.In line with the existing evidence, inequity in child cognitive development by wealth quintile appears from early childhood and persists through early schooling. Results from a longitudinal study in Bangladesh [Overall, home quality environment and maternal factors were consistently the most important mitigating factors of the wealth gap in cognitive development, while child growth and attendance to school are heterogeneous across countries and ages. Our findings showed that home stimulation reduced 10 − 42% of the observed wealth gap in cognitive development, which was aligned with a range of 18 − 37% documented in literature [While previous studies included only maternal education, we were able to examine the effects of maternal IQ and mental health which were strongly associated with child development in our analysis. The mitigating effects of early child physical growth (measuring at different time points) on disparity in child cognitive development also differ over time across countries studied in the literature. For example, HAZ was a significant mediator in reduction of 10–20% wealth gap in Indonesia, Senegal, and India at early childhood [The relatively small gaps in social emotional developments were similar in magnitude (0.2–0.3 SD) to the results reported in the Colombia [This study has some important limitations. Since the study was conducted in rural area, we are not able to compare difference between rural and urban setting as well as the contribution of residence area in wealth disparity. We did not however observe any differences associated with ethnicity in this rural population. Social emotional development was also measured by caregiver reports, which might be influenced by culture and may be affected by recall bias. Although we also did not measure maternal trauma which could influence child cognitive and social emotional development, we had measures of depression that were extremely low [In conclusion, our study finds significant wealth disparities in child development in Vietnam. The quality of the home environment, maternal factors, and child HAZ were important mitigating factors of the disparities in cognitive development and represent potential areas of intervention for reducing wealth disparities in this population. Our findings have important public health and policy implications. Specifically, there is an urgent need to develop and implement multidisciplinary poverty alleviation strategies that are targeted to benefit families with young children. Special attention on improving the quality of home environment, investments in education, and improving access to nutritious food and quality health care especially during the critical windows namely the first 1000 days is needed to ensure that all children meet their full developmental potential.