Survey on changes in colorectal cancer screening participation at Minamisoma city after the Great East Japan Earthquake using clustering analysis

Participation in colorectal cancer (CRC) screening is important. However, detailed analyses of pre- and post-disaster screening participation is lacking. We classified a population in terms of CRC screening participation pattern before and after the Great East Japan Earthquake and identified factors that are important in classifying people into such groups. Retrospective observational study We analyzed 21,578 people who were consistently registered in the basic resident register of Minamisoma between 2009 and 2018, using non-hierarchical clustering with the k-means method. After clustering analysis, we identified the factors that distinguish groups with different post-disaster participation changes by classes with high and low pre-disaster participation rates using LightGBM. Transition in screening participation rate was divided into four classes. Classes 1 and 2 had high pre-disaster participation; Class 1 recovered after a decline, while Class 2 stayed low, mainly among those still evacuated. The factors separating the two groups were age, sex, and evacuation status. Class 3 and 4 had low pre-disaster rates; Class 3 increased participation post-disaster, especially among individuals under 53 years old. The factors separating the two groups were age and sex. Our analysis revealed that CRC screening participation declined among evacuees who had previously participated in screening but increased among older individuals who had not participated before the disaster. Post-disaster screening strategies should be tailored to these groups.