title: Increase of colon and rectal cancer incidence rates in Japan: trends in incidence rates in Miyagi Prefecture, 1959-1997.
abstract: BACKGROUND
  During recent decades, colorectal cancer incidence rates have been rapidly increasing in Japan. To investigate trends in colorectal cancer incidence rates, we analyzed incidence data during 39 years between 1959 and 1997 in Miyagi Prefecture, Japan.
  
  
  METHODS
  Using age-period-cohort models, we evaluated the effects of time period and cohort on colon and rectal cancer incidence. Model fitting was based on eleven 5-year age groups (30-34 to 80-84), eight 5-year time periods, and 18 overlapping birth cohorts of 10 years each.
  
  
  RESULTS
  The analysis found a significant (p=0.04) and upward period effect on female colon cancer incidence, and a significant (p<0.01) and upward cohort effect on male colon cancer incidence. An upward period effect was also observed for male colon cancer incidence without significance. For rectal cancer incidence, a significant cohort effect was found among both males and females.
  
  
  CONCLUSIONS
  In light of known risk factors of colorectal cancer, the effects of period and cohort might be related to the change in the prevalence of risk factors such as high intake of meat and animal fat, and obesity. The improved diagnostic procedures including the spread of cancer screening might be responsible for the period effect. Although the significant cohort effects may give a caution for a continuous increase of colorectal cancer incidence, the future trend may be influenced by the period-related factors. Successive monitoring of cancer incidence and prevalence of risk factors is required.
authors.affiliation: Division of Community Health, School of Health Sciences, Tohoku University Faculty of Medicine, Sendai. adym@mail.tains.tohoku.ac.jp
authors.forename: Yuko
authors.initials: Y
authors.lastname: Minami
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Nishino
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Tsubono
authors.forename: Ichiro
authors.initials: I
authors.lastname: Tsuji
authors.forename: Shigeru
authors.initials: S
authors.lastname: Hisamichi
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003110:Colonic Neoplasms / Q000453:epidemiology*; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D012004:Rectal Neoplasms / Q000453:epidemiology*; D012189:Retrospective Studies