When diagnosed by LM, the reductions in age- and gender-adjusted Hb levels were most strongly associated with the presence of a mixed infection (-1.2 g/dl, CL95: 0.9–1.4, p < 0.001), followed by P. malariae (-0.6 g/dl, CL95: 0.3–0.9, p < 0.001), P. falciparum (-0.5 g/dl, CL95: 0.4–0.7, p < 0.001) and P. vivax single infections (-0.3 g/dl, CL95: 0.1–0.5, p = 0.005). This evidence concerns the gene GSTM1 and infection.