Multi-country analysis of the effects of diarrhoea on childhood stunting

Abstract

Diarrhoea is an important cause of death and illness among children in developing countries; however, it remains controversial as to whether diarrhoea leads to stunting. We conducted a pooled analysis of nine studies that collected daily diarrhoea morbidity and longitudinal anthropometry to determine the effects of the longitudinal history of diarrhoea prior to 24 months on stunting at age 24 months. Data covered a 20-year period and five countries. We used logistic regression to model the effect of diarrhoea on stunting. The prevalence of stunting at age 24 months varied by study (range 21-90%), as did the longitudinal history of diarrhoea prior to 24 months (incidence range 3.6-13.4 episodes per child-year, prevalence range 2.4-16.3%). The effect of diarrhoea on stunting, however, was similar across studies. The odds of stunting at age 24 months increased multiplicatively with each diarrhoeal episode and with each day of diarrhoea before 24 months (all P < 0.001). The adjusted odds of stunting increased by 1.13 for every five episodes (95% CI 1.07-1.19), and by 1.16 for every 5% unit increase in longitudinal prevalence (95% CI 1.07-1.25). In this assembled sample of 24-month-old children, the proportion of stunting attributed to >or=5 diarrhoeal episodes before 24 months was 25% (95% CI 8-38%) and that attributed to being ill with diarrhoea for >or=2% of the time before 24 months was 18% (95% CI 1-31%). These observations are consistent with the hypothesis that a higher cumulative burden of diarrhoea increases the risk of stunting.

Figure 1

Prevalence of stunting by study as a function of age. Each panel represents a separate study. The y-axis is the prevalence of stunting (%), and the x-axis is age in months. We calculated height-for-age using the 2006 WHO growth reference, and defined stunting as two standard deviations below the growth reference

Figure 2

Relationship between the cumulative burden of diarrhoea prior to 24 months of age and the log odds of stunting at 24 months of age. We calculated the log odds of stunting for these panels as log (y_i + 0.5/n_i − y_i + 0.5) across unit intervals of cumulative diarrhoeal incidence (per episode of child-year) and one percent intervals in the longitudinal prevalence of diarrhoea, where y_i represents the number of stunted children at each interval and n_i represents the total number of children in that same interval. The size of the circles is proportional to the square root of the number of children in each interval. Panel A: association between diarrhoeal incidence before 24 months and the log odds of stunting at 24 months of age. Panel B: association between longitudinal diarrhoeal prevalence before 24 months and the log odds of stunting at 24 months of age

Figure 3

Effect of diarrhoeal incidence prior to 24 months on stunting at 24 months of age. Point estimates of the effect of diarrhoeal incidence on stunting at 24 months are shown for each study. The size of the square around the point estimate is proportional to sample size. The lines represent 95% CI. In the pooled estimate, represented by a diamond, the odds of stunting at 24 months increased by 1.13 when diarrhoeal incidence prior to 24 months increased by five episodes (95% CI 1.07 to 1.19)

Figure 4

Odds ratio of stunting at 24 months of age across categories of diarrhoeal incidence and longitudinal prevalence of diarrhoea before 24 months. Panel A: effect of diarrhoeal incidence before 24 months by category on the odds of stunting at 24 months. The reference group is comprised of children who had fewer than five episodes before 24 months. The squares represent estimated odds ratio and the vertical segments represent their corresponding 95% CI. Panel B: effect of longitudinal diarrhoeal prevalence before 24 months by category on the odds of stunting at 24 months. The reference group is comprised of children who had a longitudinal diarrhoeal prevalence of 1% before 24 months. The squares represent estimated odds ratio and the vertical segments represent their corresponding 95% CI

Figure 5

Effects of the longitudinal prevalence of diarrhoea in the first 24 months on stunting at 24 months of age. Point estimates of the effect of longitudinal diarrhoea prevalence on stunting at 24 months are shown for each study. The size of the square around the point estimate is proportional to sample size. The lines represent 95% CI. In the pooled estimate, represented by a diamond, the odds of stunting at 24 months increased by 1.16 when the longitudinal prevalence of diarrhoea increased by 5% (95% CI 1.07–1.25)

Figure 6

Reversibility of stunting at 24 months of age in stunted children at 6, 12 and 18 months of age. This is a multipanel scatterplot figure of height-for-age at 24 months of age and height-for-age at 6, 12 and 18 months of age. The broken lines indicate 2 SD below the international reference. Filled circles identify children who were not stunted at 24 months but who were stunted at earlier ages

Figure A1

Results of various logistic regression models