Incidence and risk factors of colorectal cancer based on 56 324 health checkups: A 7‐year retrospective cohort study

Background and Aim Although mortality rates of colorectal cancer (CRC) have been increasing in Japan, its screening rates remain stagnant at 19.2% among Japanese population aged > 40 years in 2014. To evaluate the importance of CRC screening by fecal occult blood test (FOBT), this study estimated the incidence of FOBT‐positivity and CRC by sex–age stratification and clarified the risk factors for CRC. Methods Between 2007 and 2014, 56 324 residents (21 517 men and 34 807 women) were enrolled in this study. The sex–age‐stratified incidence rates of FOBT‐positivity and CRC were estimated by records from health checkups and colonoscopy. Regarding CRC incidence rate in particular, positive predictive value was adopted to adjust bias of FOBT‐positivity that did not undergo colonoscopy by person‐year method. To investigate the risks of CRC onset, a nested case–control study with 1:10 person‐matching on sex and age was performed. Results Incidence rates of FOBT‐positivity and CRC are 4183/100 000 person‐year (100 Kpy) and 141.3/100 Kpy, respectively. In both cases, men has higher incidence rate than women (1.3 times for FOBT; 4977 vs 3718/100 Kpy and 2.3 times for CRC; 217.0 vs 96.4/100 Kpy). Conclusions The records from health checkups were useful to estimate incidence rates of CRC with this procedure. The age‐stratified incidence rate indicated the importance of CRC screening by FOBT, especially for men and those aged > 50 years. Additionally, it is strongly recommended to do further investigation if positive for initial FOBT screening especially for those who are > 70 years.