title: Systematic review: worldwide variation in the frequency of coeliac disease and changes over time.
abstract: BACKGROUND
  Coeliac disease (CD), originally thought to be largely confined to Northern Europe and Australasia and uncommon in North America and the Middle East, is now recognised to be equally common in all these countries. It is still thought to be rare in the Orient and Sub-Saharan Africa.
  
  
  OBJECTIVE
  To assess geographical differences and time trends in the frequency of CD.
  
  
  METHODS
  Medline and Embase searches were conducted on 10 November 2012, from 1946 and 1980 respectively, using the key words: coeliac disease or celiac disease + prevalence or incidence or frequency.
  
  
  RESULTS
  There were significant intra- and inter-country differences in the prevalence and incidence of CD. Only 24 ethnic Chinese and Japanese patients have been reported in the English literature. Of CD-associated HLA DQ antigens, DQ2 occurs in 5-10% of Chinese and sub-Saharan Africans, compared to 5-20% in Western Europe. DQ8 occurs in 5-10% of English, Tunisians and Iranians, but in <5% of Eastern Europeans, Americans and Asians. The prevalence and incidence of both clinically and serologically diagnosed CD increased in recent years. These geographical and temporal differences seem genuine, although variable indices of suspicion and availability of diagnostic facilities are confounding factors.
  
  
  CONCLUSIONS
  Coeliac disease is increasing in frequency, with significant geographical differences. Although few cases have been described to date in the Orient and Sub-Saharan Africa, there is a significant prevalence of HLA DQ2 and wheat consumption is of the same order as that in Western Europe. CD may therefore become more common in the future in these countries.
authors.affiliation: Department of Gastroenterology, St George's Hospital, London, UK. jykang@sgul.ac.uk
authors.forename: J Y
authors.initials: JY
authors.lastname: Kang
authors.forename: A H Y
authors.initials: AH
authors.lastname: Kang
authors.forename: A
authors.initials: A
authors.lastname: Green
authors.forename: K A
authors.initials: KA
authors.lastname: Gwee
authors.forename: K Y
authors.initials: KY
authors.lastname: Ho
mesh_terms: D002446:Celiac Disease / Q000453:epidemiology* / Q000235:genetics; D020022:Genetic Predisposition to Disease; D006801:Humans; D015994:Incidence; D015995:Prevalence; D013997:Time Factors