Year: 2026
Type: preprint
Abstract: Anaemia and malaria remain concentrated among children living in poorer households in Nigeria, but the extent to which the wealth gradient in anaemia operates through current malaria parasitaemia is uncertain. We used three nationally representative surveys to estimate a clearly defined parasitaemia-mediated component of the association, while recognising that anaemia has multiple infectious, nutritional, genetic, and social causes. We analysed de facto children aged 6-59 months in the 2010, 2015, and 2021 Nigeria Malaria Indicator Surveys. Within each survey, we contrasted children in the poorest quintile with children in the richer and richest quintiles. The outcome was altitude-adjusted anaemia and the mediator was microscopy-confirmed parasitaemia. Weighted outcome and mediator models adjusted for child age and sex, maternal education, urban residence, geopolitical zone, household size, rainy-season interview, and altitude. We standardized interventional total, direct, and indirect effects using g-computation. Missing data were addressed with 20 chained-equation imputations; uncertainty used 1,000 Rao-Wu survey-bootstrap replicates. Analytic samples included 3,307, 3,643, and 6,572 children in 2010, 2015, and 2021. The multiple-imputation total risk difference was 11.0 (95% CI 4.1 to 17.9) percentage points in 2015 and 12.5 (95% CI 8.4 to 16.6) points in 2021; corresponding parasitaemia-mediated indirect differences were 3.4 (95% CI 1.4 to 5.4) and 2.0 (95% CI 1.1 to 2.9) points. The 2010 total-effect interval included zero. Proportion-mediated estimates were withheld for 2010 and 2015 because of unstable total-effect denominators. The poorest-to-richer/richest contrast was associated with higher anaemia risk in 2015 and 2021. A smaller positive component was compatible with mediation through microscopy-confirmed parasitaemia. Because wealth, parasitaemia, and haemoglobin were measured in the same survey visit, the estimates require assumptions about temporal ordering and unmeasured mediator-outcome confounding; they do not establish that eliminating parasitaemia would remove the observed anaemia inequality.
Source: medRxiv
Language: English
Topic: Malaria Research and Control
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W7225721377