Objective  To examine influencing factors for colorectal cancer (CRC) and precancerous lesion among elderly residents in Yangpu district of Shanghai city and to provide references for developing intervention measures.

  Methods  During January 2015 – December 2017, we conducted CRC screening (including questionnaire interview, fecal occult blood test and enteroscopy for the residents identified with high risk of CRC) among 20 000 residents recruited in communities of Yangpu district of Shanghai city using random cluster sampling each year. By the end of the three waves of the screening, we enrolled 6 154 residents aged 65 years and above and completing the screening into a cohort for a follow-up study, of which 46 diagnosed as CRC and 106 as precancerous lesions were assigned into a case group and the others into a control group. Multivariate conditional logistic regression model was used to analyze main influencing factors of CRC and precancerous lesions in the residents being followed up.

  Results  Compared to the controls, the CRC cases reported significantly higher ratios for history of chronic constipation (19.57% vs. 7.73%), mucus or blood stool (13.04% vs. 1.92%), and suffering from tumors other than CRC (41.30% vs. 4.82%) (all P < 0.05). The reported proportion of having defecation every day was significantly lower in the CRC cases than in the controls (78.26% vs. 89.04%) (χ² = 5.112, P = 0.024). In comparison with the controls, the cases with precancerous lesions reported significantly higher ratios of histories of chronic diarrhea (8.49% vs. 4.18%), mucus or blood stool (5.66% vs. 1.92%), intestinal polyps (14.15% vs. 3.33%), colorectal cancer in first degree relatives (14.15% vs. 4.27%), lower gastrointestinal inflammation (15.09% vs. 4.48%), current smoking (16.04% vs. 8.55%), and consumption of chicken, duck and other poultry meat at least 4 days every week (8.49% vs. 5.63%) (all P < 0.05), but significantly lower ratios of aged 75 years and above (5.66% vs. 15.41%) and consumption of leafy vegetables at least 6 days every week (53.77% vs. 66.14%) (both P < 0.05). The results of multivariate conditional logistic regression analysis indicated that histories of mucus or blood stool, suffering from schistosomiasis and non-colorectal cancer tumor were risk factors for colorectal cancer among the participants and that aged 65 – 74 years, history of intestinal polyps, the history of colorectal cancer in first-degree relatives, history of lower gastrointestinal inflammation, and consumption of chicken, duck and other poultry meat for 2 – 3 days every week were risk factors for precancerous lesion; while, consumption of bean products for 2 – 3 days every week was a protective factor against precancerous lesion among the participants.

  Conclusion  For the elderly residents in Yangpu district of Shanghai city, histories of mucous or bloody stool, schistosomiasis and non-colorectal cancer tumor are main risk factors of colorectal cancer and age, history of intestinal polyps, history of colorectal cancer in first-degree relatives, lower gastrointestinal inflammation and consumption of the poultry meat and bean products are main influencing factors of colorectal precancerous lesion.