title: Vitamin D deficiency and age at menarche: a prospective study.
abstract: BACKGROUND
  Early menarche is a risk factor for cardiometabolic disease and cancer. Latitude, which influences sun exposure, is inversely related to age at menarche. This association might be related to vitamin D, but to our knowledge it has not been investigated in prospective epidemiologic studies.
  
  
  OBJECTIVE
  We studied the association between vitamin D status and the occurrence of menarche in a prospective study in girls from Bogota, Colombia.
  
  
  METHODS
  We measured plasma 25-hydroxyvitamin D [25(OH)D] concentrations in a random sample of 242 girls (mean ± SD age: 8.8 ± 1.6 y) and followed them for a median of 30 mo. Girls were asked periodically about the occurrence and date of menarche. Baseline 25(OH)D concentrations were categorized as <50 nmol/L (deficient), ≥50 and <75 nmol/L, or ≥75 nmol/L (sufficient). The incidence of menarche was compared between groups by using time-to-event analyses.
  
  
  RESULTS
  A total of 57% of girls in the vitamin D-deficient group reached menarche during follow-up compared with 23% of girls in the vitamin D-sufficient group (P-trend = 0.0004). The estimated mean (±SE) ages at menarche in the same groups were 11.8 ± 0.2 y and 12.6 ± 0.2 y, respectively (P = 0.0009). After adjustment for baseline age and BMI-for-age z score in a Cox proportional hazards model, the probability of menarche was twice as high in vitamin D-deficient girls than in girls who were vitamin D-sufficient (HR: 2.05; 95% CI: 1.03, 4.07; P = 0.04). Similar results were obtained in girls aged ≥9 y at baseline (HR: 2.39; 95% CI: 1.14, 5.00; P = 0.02).
  
  
  CONCLUSIONS
  Vitamin D deficiency is associated with earlier menarche.
authors.affiliation: Department of Environmental Health Sciences, University of Michigan School of Public Health, Ann Arbor, MI 48109, USA. villamor@umich.edu
authors.forename: Eduardo
authors.initials: E
authors.lastname: Villamor
authors.forename: Constanza
authors.initials: C
authors.lastname: Marin
authors.forename: Mercedes
authors.initials: M
authors.lastname: Mora-Plazas
authors.forename: Ana
authors.initials: A
authors.lastname: Baylin
mesh_terms: D015652:25-Hydroxyvitamin D 2 / Q000097:blood; D000367:Age Factors; D015992:Body Mass Index; D002112:Calcifediol / Q000097:blood; D002648:Child; D002657:Child Development; D002675:Child, Preschool; D003105:Colombia / Q000453:epidemiology; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008572:Menarche; D016016:Proportional Hazards Models; D011446:Prospective Studies; D011629:Puberty, Precocious / Q000453:epidemiology / Q000209:etiology*; D012720:Severity of Illness Index; D014808:Vitamin D Deficiency / Q000097:blood / Q000453:epidemiology* / Q000503:physiopathology*
chemical_list: D015652:25-Hydroxyvitamin D 2; D002112:Calcifediol