Malnutrition kills directly, not indirectly

Abstract

Robert Black and colleagues (Jan 19, p 243)1Black RE Allen LH Bhutta ZA et al.Maternal and child undernutrition: global and regional exposures and health consequences.Lancet. 2008; 371: 243-260Summary Full Text Full Text PDF PubMed Scopus (3955) Google Scholar highlight the importance of nutrition for child survival. In fact, nutrition is even more important than the paper indicates. Their estimate of the specific contribution of protein-energy malnutrition, measured as low weight for age, to mortality in children aged 1–5 years is 19%—ie, substantially lower than the previous estimate of 53%.2Pelletier DL Frongillo Jr, EA Schroeder D Habicht JP The effects of malnutrition on child mortality in developing countries.Bull World Health Organ. 1995; 73: 443-448PubMed Google Scholar, 3Caulfield LE de Onis M Blössner M Black RE Undernutrition as an underlying cause of child deaths associated with diarrhea, pneumonia, malaria, and measles.Am J Clin Nutr. 2004; 80: 193-198PubMed Scopus (642) Google Scholar Although some explanations are postulated for the discrepancy, none is empirically investigated. The earlier estimate modelled the relative risks on the basis of the synergism of malnutrition and infection. Malnutrition kills children by increasing case fatality of common childhood infections, not by increasing their incidence.4Pelletier DL Frongillo Jr, EA Habicht JP Epidemiologic evidence for a potentiating effect of malnutrition on child mortality.Am J Public Health. 1993; 83: 1130-1133Crossref PubMed Scopus (307) Google Scholar Thus, malnutrition is a direct, immediate cause, not an underlying, indirect cause of death: malnourished children who are ill die because they are malnourished. The relative risks estimated by the appropriate equation for this synergistic mechanism, using appropriate indicators of protein-energy malnutrition, are so consistent across countries and study teams2Pelletier DL Frongillo Jr, EA Schroeder D Habicht JP The effects of malnutrition on child mortality in developing countries.Bull World Health Organ. 1995; 73: 443-448PubMed Google Scholar, 3Caulfield LE de Onis M Blössner M Black RE Undernutrition as an underlying cause of child deaths associated with diarrhea, pneumonia, malaria, and measles.Am J Clin Nutr. 2004; 80: 193-198PubMed Scopus (642) Google Scholar that they can only be due to an unconfounded biological mechanism, unaffected by incidences of illness or malnutrition. The equations used to derive relative risks by Black and colleagues are purely descriptive. Until further analyses are done, using a biologically appropriate method, the synergistic figure—53% of deaths among 1–5-year-olds caused directly by protein-energy malnutrition—should be used so that policy makers have a figure that reflects a direct cause of mortality, particularly since direct causes receive higher priority in health resource allocation than do underlying causes. I declare that I have no conflict of interest. Malnutrition kills directly, not indirectly – Authors' replyThe figure of more than 50% of child deaths attributed to underweight, first published by Pelletier and colleagues,1 used data from prospective studies of children aged 6–59 months and estimated the population-attributable risk for this age-group. Unfortunately, this figure has been misapplied to all children aged 0–59 months. Such extrapolation is inappropriate because the prevalence of underweight in early infancy is much lower than at older ages, and the causes of death and their relation to undernutrition are very different. Full-Text PDF