title: Regional differences in vitamin D levels and incidence of food-induced anaphylaxis in South Korea.
abstract: BACKGROUND
  Previous studies have suggested low vitamin D as a potential risk factor for food allergy/anaphylaxis. However, few studies have investigated the association between vitamin D and food-induced anaphylaxis (FIA) in South Korea.
  
  
  OBJECTIVE
  To examine regional differences in serum vitamin D levels and FIA incidence.
  
  
  METHODS
  We used nationwide data collected from 2011 to 2013. Data on vitamin D were obtained from the Korea National Health and Nutrition Examination Survey; data on FIA were obtained from the Health Insurance and Assessment Service. Districts were grouped into region 1 (lower solar radiation) and region 2 (higher solar radiation). We examined differences in FIA incidence and vitamin D levels between the regions, adjusting for age.
  
  
  RESULTS
  The study included 2,814 patients with FIA and 15,367 people with available serum vitamin D measurements. Age-adjusted FIA incidence was 2.2 per 100,000 person-years in region 1 and 1.8 per 100,000 person-years in region 2 (relative risk, 1.23; 95% confidence interval, 1.09-1.39). Age-adjusted serum vitamin D levels were 16.5 ng/mL in region 1 and 17.8 ng/mL in region 2 (mean difference, 1.3 ng/mL; 95% confidence interval, 0.9-1.9). After stratification by age, sex, and area of residence, region 1 still had higher FIA incidence and lower vitamin D levels than region 2.
  
  
  CONCLUSIONS
  The present study found a higher incidence of FIA in regions with lower vitamin D levels in the population. Further investigation is necessary to identify any direct associations between vitamin D and food allergy/anaphylaxis.
authors.affiliation: Department of Preventive Medicine and Public Health, Ajou University School of Medicine, Suwon, South Korea.
authors.forename: Si-Heon
authors.initials: SH
authors.lastname: Kim
authors.affiliation: Department of Allergy and Clinical Immunology, Ajou University School of Medicine, Suwon, South Korea.
authors.forename: Ga-Young
authors.initials: GY
authors.lastname: Ban
authors.affiliation: Department of Allergy and Clinical Immunology, Ajou University School of Medicine, Suwon, South Korea.
authors.forename: Hae-Sim
authors.initials: HS
authors.lastname: Park
authors.affiliation: Department of Allergy and Clinical Immunology, Ajou University School of Medicine, Suwon, South Korea.
authors.forename: Su-chin
authors.initials: SC
authors.lastname: Kim
authors.affiliation: Department of Allergy and Clinical Immunology, Ajou University School of Medicine, Suwon, South Korea. Electronic address: ye9007@ajou.ac.kr.
authors.forename: Young-Min
authors.initials: YM
authors.lastname: Ye
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000485:Allergens / Q000145:classification / Q000276:immunology; D000707:Anaphylaxis / Q000097:blood* / Q000453:epidemiology* / Q000276:immunology; D002648:Child; D005260:Female; D005502:Food / Q000009:adverse effects*; D005512:Food Hypersensitivity / Q000097:blood* / Q000453:epidemiology* / Q000276:immunology; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D062486:Public Health Surveillance; D056910:Republic of Korea / Q000453:epidemiology; D012307:Risk Factors; D012424:Rural Population; D014505:Urban Population; D014807:Vitamin D / Q000097:blood*; D055815:Young Adult
chemical_list: D000485:Allergens; D014807:Vitamin D