title: Association of vitamin D deficiency, season of the year, and latent tuberculosis infection among household contacts.
abstract: OBJECTIVE
  Vitamin D (VD) enhances the immune response against Mycobacterium tuberculosis in vitro, and VD deficiency has been described in patients with active tuberculosis (TB). However, the role of hypovitaminosis D in the pathogenesis of early TB infection acquisition is unclear. We aimed to evaluate the association of VD deficiency, season of the year, and latent TB infection in household contacts (HHC), given that this is a potentially modifiable condition often related to nutritional deficiencies and lack of sun exposure.
  
  
  METHODS
  We prospectively enrolled new pulmonary TB cases (n = 107) and their HHC (n = 144) over a 2-year period in Santiago, Chile. We compared plasma 25-hydroxycholecalciferol (25OHD) levels and examined the influence of season, ethnic background, living conditions, and country of origin.
  
  
  RESULTS
  Over 77% of TB cases and 62.6% of HHC had VD deficiency (<20 ng/ml). Median 25OHD concentration was significantly lower in TB cases than in HHC (11.7 vs. 18.2 ng/ml, p<0.0001). Migrants HHC had lower 25OHD levels than non-migrants (14.6 vs. 19.0 ng/ml, p = 0.026), and a trend towards a higher burden of latent TB infection (52.9% vs. 35.2%, p = 0.066). Multivariate analysis found VD deficiency in HHC was strongly associated with being sampled in winter/spring (adOR 25.68, 95%CI 7.35-89.7), corresponding to the seasons with lowest solar radiation exposure. Spring enrollment-compared with other seasons-was the chief risk factor for latent TB infection in HHC (adOR 3.14, 95%CI 1.28-7.69).
  
  
  CONCLUSIONS
  Hypovitaminosis D was highly prevalent in TB cases and also in HHC. A marked seasonality was found for both VD levels and latent TB in HHC, with winter being the season with lowest VD levels and spring the season with the highest risk of latent TB infection.
authors.affiliation: Departamento de Enfermedades Infecciosas del Adulto, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile.
authors.forename: María Elvira
authors.identifier: http://orcid.org/0000-0002-7223-9665
authors.initials: ME
authors.lastname: Balcells
authors.affiliation: Departamento de Laboratorios Clínicos, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile.
authors.forename: Patricia
authors.initials: P
authors.lastname: García
authors.affiliation: Departamento de Laboratorios Clínicos, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile.
authors.forename: Camila
authors.initials: C
authors.lastname: Tiznado
authors.affiliation: Departamento de Salud Pública, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile.
authors.forename: Luis
authors.initials: L
authors.lastname: Villarroel
authors.affiliation: Departamento de Laboratorios Clínicos, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile.
authors.forename: Natalia
authors.initials: N
authors.lastname: Scioscia
authors.affiliation: Departamento de Enfermedades Infecciosas del Adulto, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile.
authors.forename: Camila
authors.initials: C
authors.lastname: Carvajal
authors.affiliation: Departamento de Enfermedades Infecciosas del Adulto, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile.
authors.forename: Francesca
authors.initials: F
authors.lastname: Zegna-Ratá
authors.affiliation: Programa de Microbiología y Micología, Facultad de Medicina, Universidad de Chile, Santiago, Chile.
authors.forename: Mariluz
authors.initials: M
authors.lastname: Hernández
authors.affiliation: Departamento de Laboratorios Clínicos, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile.
authors.forename: Paulina
authors.initials: P
authors.lastname: Meza
authors.affiliation: Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile.
authors.forename: Luis F
authors.initials: LF
authors.lastname: González
authors.affiliation: Servicio de Respiratorio, Hospital San Borja Arriarán, Santiago, Chile.
authors.forename: Carlos
authors.initials: C
authors.lastname: Peña
authors.affiliation: Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile.
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Naves
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D017714:Community-Acquired Infections; D003430:Cross-Sectional Studies; D005191:Family Characteristics; D005260:Female; D006801:Humans; D055985:Latent Tuberculosis / Q000097:blood / Q000635:transmission*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D012621:Seasons; D014808:Vitamin D Deficiency / Q000097:blood / Q000150:complications*
chemical_list: D015415:Biomarkers