Vitamin D status and risk of incident tuberculosis disease: a systematic review and individual participant data meta-analysis
BackgroundFew studies have evaluated the association between pre-existing vitamin D deficiency (VDD) and incident TB. We assessed the impact of baseline vitamin D on TB risk. MethodsWe assessed the association between baseline vitamin D and incident TB in a prospective cohort of 6751 household contacts of TB patients in Peru. We also conducted a one-stage individual participant data meta-analysis searching PubMed and Embase for studies of vitamin D and TB until December 31, 2017. We included studies that assessed vitamin D before TB diagnosis. We defined VDD as 25-(OH)D <50 nmol/L, insufficiency as 50-75 nmol/L and sufficiency as >75nmol/L. We estimated the association between vitamin D and incident TB using conditional logistic regression in the Peru cohort and generalized linear mixed models in the meta-analysis. FindingsIn Peru, baseline VDD was associated with a statistically insignificant increase in incident TB (aOR 1{middle dot}70, 95% CI 0{middle dot}84-3{middle dot}46; p=0{middle dot}14). We identified seven studies for the meta-analysis and analyzed 3544 participants. Individuals with VDD and very low vitamin D (<25nmol/L) had increased TB risk (aOR 1{middle dot}48, 95% CI 1{middle dot}04-210;p=0{middle dot} 03 and aOR 2 08, 95% CI 0{middle dot}88-4{middle dot}92; p trend=002 respectively). Among HIV-positive patients, VDD and very low vitamin D conferred a 2-fold (aOR 2.18, 95% CI 1{middle dot} 22-3{middle dot}90; p=0{middle dot} 01) and 4-fold (aOR 4{middle dot}28, 95% CI 0{middle dot}85-21{middle dot}44; p trend=0{middle dot}01) increased risk of TB respectively. InterpretationOur findings suggest vitamin D predicts TB risk in a dose-dependent manner and vitamin D supplementation may play a role in TB prevention. FundingNational Institute of Health (NIH), National Institute of Allergy and Infectious Diseases (NIAID), National Institute on Drug Abuse (NIDA), National Institute of Mental Health (NIMH), International Maternal Pediatric Adolescent AIDS Clinical Trials Group (IMPAACT), Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institute of Dental and Craniofacial Research (NIDCR), Boehringer-Ingelheim, Bristol-Myers Squibb, Gilead Sciences, GlaxoSmithKline, Foundation, Ujala Foundation, Wyncote Foundation, NIH - Fogarty International Center Program of International Training Grants in Epidemiology Related to AIDS, NIAID Byramjee Jeejeebhoy Medical College HIV Clinical Trials Unit, NIAIDs Baltimore-Washington-India Clinical Trials Unit, National Commission on Biotechnology, the Higher Education Commission, International Research Support Initiative Program of the Higher Education Commission Government of Pakistan, the Bill and Melinda Gates Foundation, and the NIH Fogarty International Center. Research in ContextO_ST_ABSEvidence before this studyC_ST_ABSNumerous studies have found lower serum vitamin D levels among patients with active TB disease compared to healthy controls. However, research has not clarified whether low vitamin D increases TB risk or whether TB disease leads to decreased vitamin D levels. We conducted PubMed and Medline searches for all studies available through December 31, 2017 on the association between vitamin D status and TB disease. We included the following keywords: "vitamin D," "vitamin D deficiency," "hypovitaminosis D," "25-hydroxyvitamin D," "1,25-dihydroxyvitamin D," "vitamin D2," "vitamin D3," "ergocalciferol," "cholecalciferol," and "tuberculosis." We found only seven studies had prospectively evaluated the impact of baseline vitamin D levels on risk of progression to TB disease. We report here the results of a case control study nested within a large prospective longitudinal cohort study of household contacts of TB cases and the results of an individual participant data (IPD) metaanalysis of available evidence on the association between vitamin D levels and incident TB disease. Added value of this studyWe demonstrated that low vitamin D levels predicts risk of future progression to TB disease in a dose-dependent manner. Implications of all the available evidenceThese findings suggest the possibility that vitamin D supplementation among individuals at high risk for developing TB disease might play a role in TB prevention efforts.