title: Systematic review of the epidemiology of gastroesophageal reflux disease in Japan.
abstract: BACKGROUND
  Epidemiological studies of gastroesophageal reflux disease (GERD) in Japan vary in design. This systematic review examines the prevalence of GERD in Japan, distinguishing between study methodologies, and reports on changes over time and factors potentially associated with GERD.
  
  
  METHODS
  PubMed and Embase searches identified studies reporting the prevalence of GERD in the general population, primary care patients, and individuals undergoing routine health checks.
  
  
  RESULTS
  Of the twenty eligible studies, half excluded individuals taking acid-suppressive medication, so these studies would have been likely to have underestimated the prevalence by 2-3%. Nine studies reported the prevalence of at least weekly reflux symptoms (the definition closest to the Montreal definition): in seven studies this was 6.5-9.5%, but in two studies that included individuals who underwent upper gastrointestinal endoscopy the prevalence was 19.0 and 21.8%. Eight studies used symptom scores: prevalence estimates ranged from 10.2 to 29.0% in five studies using the Carlsson-Dent self-administered questionnaire (QUEST), and from 27.0 to 37.6% in three studies using the frequency scale for the symptoms of GERD. Prevalence estimates were 15.1-24.3% in three studies that reported the presence of reflux symptoms of undefined frequency. Six studies reported the prevalence of reflux esophagitis as 4.9-8.2%. Changes in prevalence over time and factors associated with reflux symptoms were inconsistent.
  
  
  CONCLUSIONS
  Few studies have reported the prevalence of GERD in Japan using standardized criteria. Thus, prevalence estimates vary substantially, reflecting differences in study populations and GERD definitions. However, seven studies reported that the prevalence of at least weekly symptoms was 6.5-9.5%, a finding which approaches that reported in Western populations (10-20%).
authors.affiliation: Shimane University Faculty of Medicine, 89-1 Enya-cho, Izumo, Shimane 693-8501, Japan. kinosita@med.shimane-u.ac.jp
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Kinoshita
authors.forename: Kyoichi
authors.initials: K
authors.lastname: Adachi
authors.forename: Michio
authors.initials: M
authors.lastname: Hongo
authors.forename: Ken
authors.initials: K
authors.lastname: Haruma
mesh_terms: D016099:Endoscopy, Gastrointestinal; D004812:Epidemiologic Methods; D015340:Epidemiologic Research Design; D004942:Esophagitis, Peptic / Q000453:epidemiology*; D005764:Gastroesophageal Reflux / Q000453:epidemiology*; D006801:Humans; D007564:Japan / Q000453:epidemiology; D015995:Prevalence; D013997:Time Factors