Infection, nutritional status, and body composition: Associations at birth and 6 months postnatally in Soweto, South Africa.

INTRODUCTION: The impact of infection on infant nutritional status, body size, and growth is well documented. However, research into the impact of infection on infant body composition is limited. Greater understanding is, therefore, needed on the effects of infection in early life. METHODS: Associations between a composite morbidity index consisting of the sum of the cumulative tallies for a range of symptoms representing infection and morbidity in the infants and nutritional status (height-for-age (HAZ), and weight-for-height (WHZ)), and body composition (fat-free mass (FFM), fat mass (FM), fat-free mass index (FFMI), and fat mass index (FMI)) at 6 months of age were investigated using hierarchical regression analysis. RESULTS: The sample comprised data between birth and 6 months postnatally, of 156 infants who were a priori born healthy in Soweto, South Africa. Morbidity, over the cumulative period of birth to 6 months, was associated with lower FMI (ß = -1.77) and lower FM (ß = -0.61), and conversely with higher FFM (ß = 0.94), in infants at 6 months. No associations were found between the morbidity index and FFMI, HAZ, and WHZ. Increased birthweight was associated with a higher FFM (ß = 0.66), HAZ (ß = 1.14), and WHZ (ß = 0.87). Finally, safely managed sanitation facilities, representative of reduced environmental exposure to fecal-oral transmission pathways were associated with a higher HAZ (ß = 1.21). DISCUSSION: Reduction in FMI and FM and exposure to inflammatory cytokines associated with mounting an immune response could alter phenotypic trajectories during to this period of plasticity. From a public health perspective, these results imply that it is important to intensify efforts to prevent infection in infants in the first 6 months postnatally, and that these efforts should concentrate on access to safely managed sanitation facilities.

Rethinking water, sanitation, and hygiene for human growth and development.

Life history theory emphasises plasticity in developmental and biological programming where conditions in early life, lead to long-term consequences for health and wellbeing. Studies linking water, sanitation, and hygiene, nutrition, and child growth and development have emphasised the optimisation of linear growth as a key metric for the evaluation of intervention efficacy. Life history characteristics pertaining to human growth and phenotypic plasticity, suggest that different developmental outcomes in early childhood may be responsive to different stimuli at different ages. Energy utilisation by the human brain, from birth through childhood, accounts for a disproportionate percentage of the resting metabolic rate. Undernutrition in early life, and its relative resultant energy deficiency, may trigger adaptive physiological mechanisms prioritising brain growth at the expense of body growth. Emphasis placed on linear growth may have impeded the significance of WASH due to excluding aspects of child development beyond height/weight. We propose that incorporating evolutionary public health and life history theory perspectives, allows for the identification of age-appropriate biological outcomes and WASH indicators, while anticipating the timing and life-course suitability of the interventions being operationalised. Finally, integrating reflections regarding context allows for the development of transformative WASH interventions.