title: Diabetes mellitus and liver cancer risk: an evaluation based on a systematic review of epidemiologic evidence among the Japanese population.
abstract: OBJECTIVE
  The potential associations of diabetes mellitus with malignant neoplasms including liver cancer have become a great concern from both clinical and preventive perspectives. Although sufficient evidence for a positive association between diabetes and liver cancer already exists, it would be informative to summarize up-to-date epidemiologic data in Japan.
  
  
  METHODS
  We systematically reviewed epidemiologic studies on diabetes and liver cancer among Japanese populations. Original data were obtained by searching the MEDLINE (PubMed) and Ichushi databases, complemented with manual searches. The evaluation was performed in terms of the magnitude of association in each study and the strength of evidence ('convincing', 'probable', 'possible' or 'insufficient'), together with biological plausibility.
  
  
  RESULTS
  We identified 19 cohort studies, one pooled-analysis of seven cohort studies, and seven case-control studies. Of 24 relative risk estimates of liver cancer for diabetes reported in those cohort studies, 17 showed a weak to strong positive association, six revealed no association and one demonstrated a weak inverse association (summary relative risk 2.10, 95% confidence interval 1.60-2.76). Ten relative risk estimates from the case-control studies showed a weak to strong positive association (n = 9) or no association (n = 1; summary relative risk 2.32, confidence interval 1.73-3.12). Overall, the summary relative risk became 2.18 (confidence interval 1.78-2.69). Heterogeneity in relative risks was significant for the difference in categories of study population (P = 0.01), but not in study type (P = 0.39) or sex (P = 0.33).
  
  
  CONCLUSIONS
  Diabetes mellitus 'probably' increases the risk of liver cancer among the Japanese population.
authors.affiliation: Department of Preventive Medicine, Faculty of Medicine, Saga University, Saga tanakake@post.saga-med.ac.jp.
authors.forename: Keitaro
authors.initials: K
authors.lastname: Tanaka
authors.affiliation: Division of Epidemiology, Department of Public Health and Forensic Medicine, Tohoku University Graduate School of Medicine, Sendai.
authors.forename: Ichiro
authors.initials: I
authors.lastname: Tsuji
authors.affiliation: Department of Public Health, Hokkaido University Graduate School of Medicine, Sapporo.
authors.forename: Akiko
authors.initials: A
authors.lastname: Tamakoshi
authors.affiliation: Department of Preventive Medicine, Kyushu University Graduate School of Medical Sciences, Fukuoka.
authors.forename: Keitaro
authors.initials: K
authors.lastname: Matsuo
authors.affiliation: Department of Preventive Medicine, Nagoya University Graduate School of Medicine, Nagoya.
authors.forename: Kenji
authors.initials: K
authors.lastname: Wakai
authors.affiliation: Department of Epidemiology and Preventive Medicine, Gifu University Graduate School of Medicine, Gifu.
authors.forename: Chisato
authors.initials: C
authors.lastname: Nagata
authors.affiliation: Department of Epidemiology and Prevention, International Clinical Research Center, National Center for Global Health and Medicine, Tokyo.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Mizoue
authors.affiliation: AXA Department of Health and Human Society, Graduate School of Medicine, The University of Tokyo, Tokyo Epidemiology and Prevention Division, Research Center for Cancer Prevention and Screening, National Cancer Center, Tokyo, Japan.
authors.forename: Manami
authors.initials: M
authors.lastname: Inoue
authors.affiliation: Epidemiology and Prevention Division, Research Center for Cancer Prevention and Screening, National Cancer Center, Tokyo, Japan.
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Tsugane
authors.affiliation: Epidemiology and Prevention Division, Research Center for Cancer Prevention and Screening, National Cancer Center, Tokyo, Japan.
authors.forename: Shizuka
authors.initials: S
authors.lastname: Sasazuki
mesh_terms: D044466:Asian People / Q000706:statistics & numerical data*; D016022:Case-Control Studies; D015331:Cohort Studies; D048909:Diabetes Complications / Q000453:epidemiology*; D005260:Female; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008113:Liver Neoplasms / Q000453:epidemiology* / Q000209:etiology*; D008297:Male; D012306:Risk
keywords: Japanese; diabetes; epidemiology; liver cancer; systematic review