Climatic conditions and child height: Sex-specific vulnerability and the protective effects of sanitation and food markets in Nepal

Environmental conditions in early life are known to have causal impacts on later health outcomes, but mechanisms and potential remedies have been difficult to discern. This paper uses the Nepal Demographic and Health Surveys (DHS) of 2006 and 2011, combined with earlier NASA satellite observations of variation in vegetation density (NDVI) at each child’s location and time of birth, to identify the trimesters of gestation and infancy during which climate variation can be linked to heights attained between 12 and 59 months of age. We find significant differences by sex of the fetus: males are most affected by conditions in their second trimester of gestation, and females in their first trimester after birth. Each 100 point difference in NDVI at those times is associated with a difference in height-for-age Z-score (HAZ) of 0.088 for boys and 0.054 for girls, an effect size that is similar to moving within the distribution of household wealth by one quintile for boys, and one decile for girls. The entire seasonal change in NDVI from peak to trough is on the order of 200-300 points, implying a seasonal effect on HAZ similar to 1-3 quintiles of household wealth. This effect is observed only in households without toilets; with toilets there is no seasonal fluctuation, implying protection against climatic changes in disease transmission. We also use data from the Nepal Living Standards Surveys on district-level agricultural production and marketing, and find a vegetation effect on child growth only in districts where households’ food consumption comes primarily from own production. Robustness tests find no evidence of selection effects, and placebo regressions reveal no significant artefactual correlations. Our findings regarding timing and sex-specificity are consistent with previous results, and the protective effect of sanitation and markets is a novel indication of the mechanisms by which households can gain resilience against adverse climatic conditions.