Double Burden of Iron Deficiency in Infancy and Low Socioeconomic Status

Abstract

OBJECTIVE: To assess change in cognitive functioning following iron deficiency in infancy, depending on socio-economic status (middle- vs. low-SES). DESIGN: Longitudinal study. SETTING: Urban community in Costa Rica (infancy phase, 1981-1984, through 19-year follow-up, 2000-2002). PARTICIPANTS: 185 individuals enrolled at 12-23 months (no preterm/low birth weight or acute/chronic health problems), assessed in infancy and at 5, 11-14, 15-18, and 19 years. 97% evaluated at 5 or 11-14 years; 78% at 15-18 or 19 years. EXPOSURE: Infancy iron status: chronic iron deficiency (iron deficiency with hemoglobin (Hb) ≤ 10.0 g/dL or, with higher Hb, not fully corrected with 3 months of iron therapy) vs. good iron status (Hb ≥ 12.0 g/dL and normal iron measures before and/or after therapy). For middle-SES, 20 chronic-iron-deficiency compared to 67 good-iron-status group. For low-SES, 33 chroniciron-deficiency compared to 65 good-iron-status group. OUTCOME MEASURES: Cognitive change over time (composite of standardized scores at each age). RESULTS: For middle-SES participants, scores averaged 101.2 in chronic-iron-deficiency vs. 109.3 in good-iron-status groups in infancy and remained 8-9 points lower through 19 years (95% CI -10.1 to -6.2). For low-SES participants, the gap widened from 10 points (93.1 v. 102.8; 95% CI for the difference, -12.8 to -6.6) to 25 points (70.4 vs. 95.3; 95% CI for the difference, 20.6 to 29.4). CONCLUSIONS: The chronic-iron-deficiency group did not catch up to the good-iron-status group in cognitive scores over time. There was a widening gap for those in low-SES families. The results suggest the value of preventing iron deficiency in infancy.