title: Obesity and liver cancer risk: an evaluation based on a systematic review of epidemiologic evidence among the Japanese population.
abstract: OBJECTIVE
  With increased interest in non-alcoholic steatohepatitis, its common co-morbid condition, obesity, has recently attracted much attention as a risk factor for liver cancer. Recent studies also suggest that obesity may play a role in the development of liver cancer in alcoholic cirrhosis or viral hepatitis and in the general population.
  
  
  METHODS
  We systematically reviewed epidemiologic studies on overweight/obesity and liver cancer among Japanese populations. Original data were obtained by searching the MEDLINE (PubMed) and Ichushi databases, complemented by 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 biologic plausibility.
  
  
  RESULTS
  Among nine cohort studies identified, five (four on patients with chronic liver disease and one on local residents) reported a weak to strong positive association, while four (one on patients with hepatitis B and three on local residents) found no association [summary relative risk for one unit increase in body mass index (kg/m(2)) 1.07, 95% confidence interval 1.03-1.10]. All three case-control studies identified (two on cirrhotic patients and one on atomic bomb survivors) reported a strong positive association (summary relative risk 1.31, 95% confidence interval 1.12-1.53). Overall, the summary relative risk was estimated at 1.13 (95% confidence interval 1.07-1.20), and overweight/obese individuals had a relative risk of 1.74 (95% confidence interval 1.33-2.28) compared with those who had normal/low weight.
  
  
  CONCLUSIONS
  We conclude that overweight or obesity 'probably' increases the risk of primary liver cancer, to a moderate degree, among the Japanese population.
authors.affiliation: Department of Preventive Medicine, Saga University, Saga, Japan. tanakake@post.saga-med.ac.jp
authors.forename: Keitaro
authors.initials: K
authors.lastname: Tanaka
authors.forename: Ichiro
authors.initials: I
authors.lastname: Tsuji
authors.forename: Akiko
authors.initials: A
authors.lastname: Tamakoshi
authors.forename: Keitaro
authors.initials: K
authors.lastname: Matsuo
authors.forename: Hidemi
authors.initials: H
authors.lastname: Ito
authors.forename: Kenji
authors.initials: K
authors.lastname: Wakai
authors.forename: Chisato
authors.initials: C
authors.lastname: Nagata
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Mizoue
authors.forename: Shizuka
authors.initials: S
authors.lastname: Sasazuki
authors.forename: Manami
authors.initials: M
authors.lastname: Inoue
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Tsugane
mesh_terms: D044466:Asian People; D005260:Female; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008113:Liver Neoplasms / Q000453:epidemiology* / Q000209:etiology*; D008297:Male; D009765:Obesity / Q000150:complications* / Q000453:epidemiology*; D012307:Risk Factors