Vitamin D Concentrations in Infancy and the Risk of Tuberculosis Disease in Childhood: A Prospective Birth Cohort in Cape Town, South Africa

Abstract

BackgroundLow vitamin D levels may increase the risk of tuberculosis disease; however, previous observational cohort studies showed variable results. We investigated the relationship between vitamin D levels in infancy and subsequent development of tuberculosis disease throughout childhood.MethodsWe enrolled pregnant women at 20–28 weeks’ gestation attending antenatal care in a periurban South African setting in the Drakenstein Child Health Study. Serum 25(OH)D concentrations were measured in newborn infants aged 6–10 weeks. Children were followed prospectively for tuberculosis infection and disease using annual tuberculin skin testing, radiographic examinations, and microbiological diagnosis with GeneXpert, culture, and smear testing. Univariable and multivariable Cox regression was performed and HRs with 95% CIs were calculated.ResultsChildren were followed for tuberculosis disease for a median of 7.2 years (IQR, 6.2–7.9). Among 744 children (<1% with human immunodeficiency virus (HIV), 21% HIV-exposed without HIV), those who were vitamin D deficient in early infancy were not at increased risk of developing tuberculosis disease (adjusted HR, .8; 95% CI, .4–1.6). Infants in the lowest vitamin D concentration tertile were at similar risk of tuberculosis as the highest tertile (adjusted HR, .7; 95% CI, .4–1.4). Vitamin D deficiency was associated with tuberculin conversion ≤2 years of age at a <30-nmol/L (adjusted OR, 1.9; 95% CI, 1.2–3.2), but not <50-nmol/L (adjusted OR, 1.5; 95% CI, .8–2.9), cutoff.ConclusionsIn a setting with hyperendemic rates of tuberculosis, vitamin D concentrations in infancy did not predict tuberculosis disease at any point in childhood. However, very low vitamin D levels were associated with tuberculin conversion in young children.