An investigation of the association between household biomass fuel smoke exposure, anaemia and stunting in children aged 12-59 months participating in the 2006-2007 Swaziland Demographic and Health Survey
Machisa, Mercilene Tanyaradzwa
Background Indoor air pollution due to use of biomass fuels (BMF) for household cooking and heating is a known risk factor of morbidity and mortality in children under the age of five years. A recent study in India suggested an association between biomass fuel smoke exposure anaemia and stunting among children under the age of five. The aim of this study was to investigate the association between BMF use, stunting and anaemia in children aged 12-59 months who participated in the 2006-2007 Swaziland Demographic and Health Survey (SDHS), whilst adjusting for potential confounders. Methods The study was cross-sectional and based on secondary data analysis of data collected through the household and women’s questionnaires in the 2006-2007 SDHS, which employed a multistage random sampling. Anthropometric measurements taken in the SDHS and the World Health Organization (WHO) 2006 Multi-Centre Child growth reference standards were used to ascertain children’s health status and the stunting outcome variable. A child, whose height-for-age ratio was below three standard deviations (SD) from the median of the WHO reference population in terms of height-for-age, was severely stunted or short for his/her age. A child, whose height-for-age ratio was between three and two SD below the median of the WHO reference population in terms of height-for-age, was mildly stunted. The exposure to BMF smoke variable was ascertained indirectly by type of fuel used for cooking. The exposure was a three category variable of cleaner fuel, outdoor BMF and indoor BMF use. All statistical analysis was done in STATA version 10. The relationship between BMF use and stunting or anaemia was determined using multinomial logistic regression analyses, whilst adjusting for potential confounding factors, identified in previous research. Results Of the 1612 children included in the study, 37% were anaemic. Nineteen percent were mildly and 18% were moderate to severely anaemic. Indoor BMF use, child age, low birth weight, mother’s age at birth, iron supplementation during pregnancy and mother’s anaemia status was significantly associated with child anaemia in univariate analysis. Outdoor BMF exposure, low birth weight, child age, mother’s anaemia status and wealth index was associated with child anaemia after adjusting for potential confounding. Overall 31% of children were stunted. Twenty percent were mildly stunted and 11% were moderate to severely stunted. Child sex, age, birth order, preceding birth interval, low birth weight, diarrhoea in preceding two weeks, anaemia status, iron supplementation during pregnancy, mother’s age at birth ,mother’s body mass index, mother’s education, wealth index, indoor BMF exposure and household crowding were each independently associated with stunting in univariate analysis. Only child sex, low birth weight and child age were significantly associated with stunting after adjusting for potential confounding. There was no evidence of an association between indoor BMF smoke exposure and child stunting after adjusting for all potential confounding factors. Conclusion This study did not find sufficient evidence to suggest that indoor BMF use is a statistically significant risk factor for anaemia or stunting in children aged 12-59 months participating in the 2006-2007 SDHS. There was however an evidence that, use of BMF outdoors significantly confers a protective effect against moderate to severe anaemia. Prospective research into these potential relationships are necessary, particularly the collection of primary data and accurate measurement of exposure to smoke emitted during BMF use for cooking and heating.