A systematic review and meta-analysis of the association between neglected tropical diseases and malnutrition: more research needed on diseases other than intestinal parasites, leishmaniasis and leprosy.

Background. According to the World Health Organization, neglected tropical diseases (NTDs) affect over two billion people worldwide. While the links between nutrition and many diseases have become clear over recent decades, NTDs have lagged behind and the linkage with nutrition is largely unknown. We conducted this systematic review with meta-analysis to determine the current knowledge on the association between NTDs and malnutrition. Methodology. PubMed, Embase, Scopus and African Journals Online databases were searched using predefined search terms. We included all original articles with a case-control design and at least one NTD. The studies had to compare nutritional parameters between infected cases and control participants. Articles that did not report original data were excluded. The quality of the studies was assessed using the Newcastle-Ottawa scale. Pooled estimates were conducted using the random effect model. The publication bias of the studies was determined by funnel plots. Q and I ² statistics were used to assess the heterogeneity of the studies. Results. After screening 1294 articles, only 16 qualified for the systematic review and 12 for meta-analysis. These predominately had a focus on soil-transmitted helminthiasis (ascariasis, hookworm diseases and trichuriasis) and schistosomiasis, with a minority concerning leishmaniasis and leprosy. Pooled estimates showed an association between intestinal parasites and stunting in children [odds ratio (OR) = 1.38, 95% confidence interval (CI): 1.14-1.66, I ² = 0%, tau² = 0]. We also identified a moderate association established between serum iron deficiency (OR = 4.67, 95% CI: 1.91-11.44, tau² = 0) and intestinal parasites. Conclusions/significance. Of the 20 NTDs, the links between diet and disease have been explored for only 4. There is a paucity of data from low- and middle-income countries and least-developed countries where the NTD burden is high. Therefore, more research into the role of malnutrition in NTDs other than intestinal parasites, leishmaniasis and leprosy is needed.