Exploring linear growth retardation in Rwandan children: Ecological and biological factors

Background: Stunted linear growth and anaemia are major public health concerns in low-income countries, with a disproportionate global burden affecting Sub-Saharan Africa. In Rwanda, stunting among children under five years of age is still high (38%) and it affects more boys compared to girls (43% vs. 33%). However, no studies have tried to explain the causes of this sex disparity so far. Furthermore, anaemia prevalence hits its peak at infancy, with 72% and 61% of children being anaemic at 6-8 and 9-11 months of age, respectively. Little is known about the causes of anaemia including the contribution of iron deficiency. Therefore, understanding the context-specific factors of poor linear growth and anaemia is key to targeting evidence-based interventions for accelerating the reduction in the magnitude of these two forms of undernutrition. Our research aimed to explore the aetiology of stunted linear growth and anaemia in the Rwandan context.

Methods: We analysed cross-sectional data of 1228 children aged 6-23 months from eight districts with a high burden of malnutrition in Rwanda collected in 2014-2015 as the baseline survey of a nutrition program. Then we conducted a longitudinal study on 192 mother-child pairs living in a rural area of one district of these eight districts. From birth to 1 year of age, anthropometric measures, morbidity, and feeding data were collected monthly. The child’s length and its potential predictors were analysed using a linear mixed model. We stratified the analysis by age ranges of 0-5, 6-12, and 0-12 months to consider the differences in the start of feeding practices. In the longitudinal study, we, further, measured haemoglobin concentration and collected blood samples from the mother-child pairs at birth and at 4 and 12 months post-partum. Ferritin, sTfR, CRP, and AGP concentrations were measured using a sandwich ELISA technique. Haemoglobin and ferritin values were adjusted for altitude and inflammation, respectively. Finally, in a methodological study, we used a convenience sample of 13 pairs of mothers and babies aged 2 to 4 months who were exclusively breastfed and healthy to assess breastmilk intake using the deuterium dose-to-mother technique.

Results: The findings from the analysis of the cross-sectional data confirmed that stunting significantly affected more boys than girls, with a prevalence of 43.3% vs. 28.0%, respectively. Being fed porridge as first weaning food as opposed to cow’s milk was a significant factor for stunting in boys solely (PR=1.44, 95% CI=1.07-1.94, p-interaction=0.048) while discontinued breastfeeding was a significant factor in girls only (PR=1.49, 95% CI=1.05-2.11, p-interaction=0.017). The results from the longitudinal study showed that children were already born with length deficits of -1.4 cm, which gradually deteriorated to -2.7 cm at 12 months of age. Significant predictors of decelerated linear growth were late initiation of breastfeeding (-0.73 cm, 95% CI: -1.45, -0.01) in the age range of 6-12 months, high breastfeeding frequency (-0.01 cm per additional feed, 95% CI: -0.02, -0.00) from 0-5 and 0-12 months, and early introduction of complementary feeding (-0.69 cm, 95% CI: -0.90, -0.49) from 0-12 months. Moreover, the duration (days) of diarrhoea or malaria illnesses significantly predicted decreased linear growth depending on the age range. Meal frequency, dietary diversity, and acceptable diet did not significantly predict linear growth. Conversely, the study confirmed a strong positive effect of birth weight and birth length on postnatal linear growth. We saw that at 4 months of age, anaemia, iron deficiency (ID), and iron deficiency anaemia (IDA) occurred in 73%, 10%, and 8%, respectively while at 12 months of age, anaemia reduced to 48% and both ID and IDA increased to 28% and 18%, respectively. At 4 and 12 months of age, ID contributed 10% and 36.5% to anaemia cases, respectively. Dietary iron intake tended to significantly predict iron deficiency (PR=0.79, 95% CI: 0.62, 1.03), but not anaemia or iron-deficiency anaemia at 12 months of age. However, the duration of being ill with malaria was significantly associated with anaemia (PR=1.05, 95% CI: 1.00-1.10), ID (PR=1.09, 95% CI: 1.04-1.15), as well as with IDA (PR=1.15, 95% CI: 1.06-1.25). In addition, the presence of inflammation predicted anaemia (PR=1.01, 95% CI: 1.01-1.10). Iron deficiency at 12 months of age occurred less often when children had higher body iron reserves at 4 months of age (PR=0.73, 95% CI: 0.59, 0.89). Lastly, the findings from a small methodological study showed that the mean breastmilk intake based on saliva samples was significantly higher than that based on urine samples (854.5 g/day vs. 812.8 g/day, p=0.029).

Conclusions: Stunted linear growth among boys is higher than among girls in Rwanda and this seems to be most strongly related to the nutritional quality of foods during the complementary feeding period. However, children in Rwanda are already born with a length deficit, which gradually deteriorates with the child’s age without any signs of catch-up growth during infancy. Late initiation of breastfeeding, high breastfeeding frequency, early introduction to complementary feeding, and the duration of diarrhoea and malaria illnesses are significant correlates of decelerated linear growth. However, none of the indicators of complementary feeding practices is significantly related to linear growth, anaemia, ID, and IDA. However, dietary iron intake is weakly associated with iron deficiency, but not with anaemia or iron deficiency anaemia. The duration of malaria infection significantly predicts anaemia, iron deficiency, and iron deficiency anaemia at 12 months of age.

Considering these findings, prenatal interventions seem to be crucial to ensure that children are born with adequate body dimensions and iron reserves, which should give a strong foundation to sustain postnatal growth and iron status. Moreover, improving the quality of complementary foods is central to prevent any deterioration of their nutritional status from 6 months of age onwards. However, to make dietary interventions effective, infectious diseases must be controlled.