Age-specific Differences in the Magnitude of Malaria-related Anemia During Low and High Malaria Seasons in Rural Zambian Children

Background: Malaria causes anemia by destruction of red blood cells and inhibition of erythropoiesis.

Objective: We assessed whether the magnitude of the malaria-specific effect on anemia differs by age, during low and high malaria seasons.

Method: In rural Zambian children participating in a pro-vitamin A efficacy trial, we estimated differences in the prevalence of anemia (defined as hemoglobin < 110 g/L for children < 60 months. and < 115 g/L in older children) by malaria status and assessed malaria-age interactions. Regression models (with anemia as the outcome) were used to model malaria-age interaction in both the low and high malaria seasons, controlling for potential confounders.

Results: Average age was 68 months at baseline ( = 820 children). In the low malaria season, anemia prevalence was 29% in malaria-negative children and 54% in malaria-positive children ( < 0.001), with no malaria-age interactions ( = 0.44). In the high malaria season, anemia prevalence was 41% in malaria-negative children and 54% in malaria-positive children ( < 0.001), with significant malaria-age interactions ( = 0.02 for anemia). Age-stratified prevalence of anemia in malaria positive versus negative children was 67.0% versus 37.1% (in children < 60 months); 57.0% versus 37.2% (in 60-69 months.); 46.8% versus 37.2% (in 70-79 months.); 37.0% versus 37.3% (in 80-89 months) and 28.0% versus 37.4% (in 90+ months).

Conclusions: Malarial anemia is most severe in younger children, especially when transmission is intense. Anemia control programs must prioritize this vulnerable group.