Seasonal aspects of weight-for-age in young children in Zimbabwe

Abstract

Objective: To identify the season with the highest prevalence of underweight among young children and to examine geographical variation in seasonality of underweight. Design: This analysis is based on monthly data from a clinic-based growth monitoring programme that forms part of the National Health Information System. A regression-based technique is used to identify seasonal patterns in both underweight prevalence and attendance nationally and in 60 different districts. Setting: The analysis covers the period 1988±1995 and is based in Zimbabwe. Subjects: The analysis is based on weight-forage measurements of Zimbabwean children less than 5 years old, who attended health centres as part of a growth monitoring programme. Results: Nationally, a small but significant increase in levels of underweight takes place during January±March. Participation in growth monitoring also varies seasonally and could account for the increase observed. No evidence of seasonal variation in underweight prevalence is found in the majority of districts studied, although 11 of the districts showed a similar pattern to the national data set. This peak in the incidence of poor nutritional status also coincides with the period of food scarcity before harvest, which is also associated with higher prevalence of diarrhoea and malaria. No differences in seasonality of under-nutrition were found between districts with predominantly subsistence agriculture and those with more commercial forms of agriculture. Conclusions: Seasonal variation in child weight-forage exists in some parts of Zimbabwe, but its effects on cross-sectional prevalence studies are likely to be small. There are no readily discernible differences between areas that show evidence of seasonality in levels of underweight and those that do not. This paper reports on seasonal variation in levels of under-nutrition in Zimbabwean infants and young children using nutritional surveillance data. Under-nutrition is defined as dietary intake below the minimum level for healthy growth and acceptable energy expenditure, and in this context is measured by the weight-forage indicator. The objectives of the study are to identify the extent of seasonal variation in under-nutrition across the whole country, to establish whether the same pattern of seasonality occurs in all parts of the country, and to identify possible reasons for the pattern observed. These objectives have several practical policy implications. First, better understanding of seasonal variation can aid the interpretation of cross-sectional prevalence surveys, particularly when comparing results from surveys that took place at different times of the year. Second, identification of seasonal patterns can guide the timing of appropriate interventions and provides an indication of the relative importance of the different causes of poor nutritional status. In Zimbabwe, the three principal influences on children's nutritional status are regarded as household food security, health environment and services, and the level of care available within the household 1. Of these, the most obvious cause of variation in child nutritional status is thought to occur through household food