Epidemiology of iron deficiency anemia in Zanzibari schoolchildren: the importance of hookworms

Abstract

Anemia is estimated to affect one-half of school-age children in developing countries. The school years are an opportune time to intervene, and interventions must be based on sound epidemiologic understanding of the problem in this age group. We report on the distribution of iron deficiency and anemia across age, sex, anthropometric indexes, and parasitic infections in a representative sample of 3595 schoolchildren from Pemba Island, Zanzibar. Iron status was assessed by hemoglobin, erythrocyte protoporphyrin (EP), and serum ferritin concentrations from a venous blood sample. Overall, 62.3% of children were anemic (hemoglobin < 110 g/L), and 82.7% of anemia was associated with iron deficiency. The overall prevalence of iron-deficient erythropoiesis (EP > 90 mumol/mol heme) was 48.5%, and the prevalence of exhausted iron stores (serum ferritin < 12 micrograms/L) was 41.3%. In bivariate analyses, iron status was slightly better in girls than in boys, and was better in children aged 7-11 y than in those older or younger. Hemoglobin but not EP or serum ferritin concentrations were lower in stunted children. Infection with malaria, Trichuris trichiura, Ascaris lumbricoides, and hookworms were all associated with worse iron status; the association with hookworms was strongest by far. In multivariate analyses, hookworm infection intensity was the strongest explanatory variable for hemoglobin, EP, and serum ferritin. Sex, malarial parasitemia, A. lumbricoides infection, and stunting were also retained in the multivariate model for hemoglobin. Twenty-five percent of all anemia, 35% of iron deficiency anemia, and 73% of severe anemia were attributable to hookworm infection; < 10% of anemia was attributable to A. lumbricoides, malaria infection, or stunting. We conclude that anthelminthic therapy is an essential component of anemia control in schoolchildren in whom hookworms are endemic, and should be complemented with school-based iron supplementation.

Age patterns in stunting and anaemia in African schoolchildren: a cross-sectional study in Tanzania

“…Anaemia is particularly prevalent among younger children. This is consistent with previous studies (Partnership for Child Development, 1998b;Stoltzfus et al, 1997b) and may be explained by the fact that the youngest children have recently experienced the high iron demand of early childhood. Among younger children, boys are more anaemic than girls, for unknown reasons.…”

“…Consistent with previous studies (Stephenson et al, 1985;Stoltzfus et al, 1997b), we found a signi®cant relationship between anaemia and hookworm infection. No relationship was observed between schistosomiasis and anaemia, which is consistent with some other studies (Be®®-Mengue et al, 1993;Olsen et al, 1998), but differs from others (Tatala et al, 1998;Stoltzfus et al, 1997b).…”

“…No relationship was observed between schistosomiasis and anaemia, which is consistent with some other studies (Be®®-Mengue et al, 1993;Olsen et al, 1998), but differs from others (Tatala et al, 1998;Stoltzfus et al, 1997b). The present study was not designed to measure intensity.…”

“…Although this study did not examine dietary intake, anecdotal evidence suggests that food intake is particularly poor in this area, and may contribute to anaemia. Malaria is also endemic in the area (NJS Lwambo, personal communication) and may also be an important contributing factor to anaemia (Tatala et al, 1998;Stoltzfus et al, 1997b;Be®®-Mengue et al, 1993).…”

“…This is thought to be a function of differential drop out of relatively disadvantaged girls leaving better-nourished girls in school (Partnership for Child Development, 1998b) or due to age-speci®c differences in catch-up growth between the sexes (Simondon et al, 1998). A reduction in the prevalence of anaemia throughout the school-aged years has also been observed, with more boys than girls being anaemic in the younger years, but anaemia becoming more common girls during adolescence (Stoltzfus et al, 1997b). Although previous studies report similar trends by age and sex, the timing of the growth spurt, especially among boys, remains ill-de®ned due to the relatively small sample size among older adolescents.…”