title: Vitamin B12 deficiency is associated with geographical latitude and solar radiation in the older population.
abstract: BACKGROUND
  Vitamin B12 and folic acid deficiency are common in the older and are associated with several conditions including anaemia, cardiovascular disease, cognitive impairment and cancer. Evidence from in vitro studies suggests that solar radiation can degrade both vitamins in the skin. Chile is the longest country in the world running perfectly North-South making it an ideal place to study potential associations of latitude and solar radiation on vitamin B12 and folic acid deficiency.
  
  
  OBJECTIVE
  The objective was to examine the association between vitamin B12 and folic acid deficiencies and latitude.
  
  
  METHODS
  Plasma samples were collected from Chileans aged 65+ years (n=1013) living across the whole country and assayed for vitamin B12 and folic acid concentrations as part of the Chilean Health Survey 2009-2010, which is a national representative sample study.
  
  
  RESULTS
  Overall, the prevalence of vitamin B12 deficiency was 11.3%, with the prevalence in the North of the country being significantly greater than in the Central and South zones (19.1%,10.5%, and 5.7%, respectively; P<0.001). The prevalence of folic acid deficiency in the whole cohort was 0.7% with no difference between the 3 geographical zones. Using logistic regression analyses, vitamin B12 deficiency was significantly associated with geographical latitude (OR 0.910 [95% confidence intervals 0.890-0.940], P<0.001) and solar radiation (OR 1.203 [95% confidence intervals 1.119-1.294], P<<0.001). These associations persisted after adjustments for confounders (OR 0.930, P<0.001 and 1.198, P=0.002, respectively).
  
  
  CONCLUSIONS
  In the Chilean population of 65+, the prevalence of vitamin B12 deficiency is associated with living closer to the Equator and solar radiation. Although degradation by solar radiation might explain this observation, further work is required to establish the potential mechanisms. In countries that routinely fortify food with folic acid, efforts to identify vitamin B12 deficiency might be more cost-efficiently targeted in areas closest to the Equator.
authors: Nephrology Division, Clinical Hospital, University of Chile, Chile.
authors: Sebastián
authors: S
authors: Cabrera
authors: Section of Acute Nephrological Procedures, Clínica Las Condes, Chile.
authors: David
authors: D
authors: Benavente
authors: Nephrology Division, Clinical Hospital, University of Chile, Chile.
authors: Miriam
authors: M
authors: Alvo
authors: Department of Rheumatology, University of Birmingham, Queen Elizabeth Hospital, UK.
authors: Paola
authors: P
authors: de Pablo
authors: Department of Nephrology, Queen Elizabeth Hospital, Birmingham, UK. Electronic address: charles.ferro@uhb.nhs.uk.
authors: Charles J
authors: CJ
authors: Ferro
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002677:Chile; D015331:Cohort Studies; D003710:Demography; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005492:Folic Acid / Q000097:blood; D005494:Folic Acid Deficiency / Q000453:epidemiology / Q000473:pathology; D006801:Humans; D008027:Light; D016015:Logistic Models; D008297:Male; D015995:Prevalence; D012867:Skin / Q000528:radiation effects; D014805:Vitamin B 12 / Q000097:blood; D014806:Vitamin B 12 Deficiency / Q000453:epidemiology* / Q000473:pathology
chemical_list: D005492:Folic Acid; D014805:Vitamin B 12
keywords: Deficiency; Folic acid; Geographical latitude; Solar radiation; Vitamin B12