Abstract Objective To explore the incidence of colon cancer risk factors, to provide a scientific basis for colon cancer prevention. Methods 1:1 matched case  control study, cases and controls were selected in three Affiliated Hospital of Central South University, paired by sex and age, the application of conditional logistic regression analysis of the study variables. The results of the multivariate analysis results often in a sitting state animal oil, edible oil, the history of gallbladder disease, appendicitis history, and first-degree relatives of a history of cancer, such as colon cancer risk factors, eat vegetables for colon cancer protective factors. Conclusion The incidence of colon cancer by eating habits of life, digestive disease history and the influence of family history of cancer.

Key words] colon cancer; risk factors; case-control study; multivariate analysis

A Case  control Study on Risk Factors of Colonic Cancer

    ZHAO Jun  shi, HUANG Min  zhu, WU Xin  yin, HE Xiao  wei

    Department of Epidemiology and Health Statistics, College of Public Health, Central South University, Changsha 410078, China

    Correspoing Author: HUANG Min  zhu, E  mail: huangminzhu_2002@163.comAbstract: Objective To discovery the major risk factors of colonic cancer and provide some reference for proper interventions of colonic cancer.Methods A case  control study including cases and controls, who were matched by age and gender, was carried out in the three hospitals of Central South University. Factors were analyzed using conditional logistic regression.Results As the results of multivariate regression, frequently being in sitting, animal oil is the primary part of cooking oil , cystic diseases, appendicitis and cancer history of first degree relatives were risk factors of colonic cancer, while frequently eating vegetable were protective factors of colonic cancer.Conclusion The life style and dietary habits, digestive diseases and the positive history of cancer in relatives were the major influencing factors of colonic cancer.

    Key words: Colonic cancer; Risk factor; Case  control study; Multivariate analysis
Colon cancer is a common malignancy worldwide in 2005, about 7.6 million people died of cancer, including colon cancer was 65.5 million, came in fourth place, behind lung, stomach and liver cancer [1]. Of colon cancer incidence in the 3 to 6, all tumors recent years, with the economic development and environmental change as well as dietary structure, lifestyle changes, the incidence rate increased significantly. Beijing, Shanghai and other major cities, the increase in incidence trend was particularly significant, the incidence rate (20 to 30) / 100 000 [2]. Colon cancer risk factors, and to develop effective prevention and control measures have become an important task in the field of public health. There is no colon cancer risk factors reported in Hunan, the Affiliated Hospital of Central South University, three 1:1 matched case-control study to examine the major risk factor for colon cancer, and provide a reference for the formulation of the colon cancer prevention and control measures.

    1 Materials and Methods

    1.1 The object of study

    Affiliated Hospital of Central South University, three (Xiangya Hospital, Second Xiangya Hospital, Xiangya Hospital) May 1, 2006 to May 1, 2007 in-patients were investigated retrospectively. The case group as confirmed by biopsy in patients with new-onset colon cancer, non-cancer patients for the same period as a control group, in accordance with the same sex, age difference of less than 3 years old pairing.

    1.2 survey content

    The content of the questionnaire in addition to general life eating habits, the disease medication history, and family history of cancer investigation.

    1.3 Survey method

    Form of face-to-face interviews conducted survey, investigators served by the uniform training of medical students, the survey clearly defined on a case-by-case basis. Description of all survey research purposes, to fight with the. The decimation questionnaire 10% repeat survey, review of the questionnaire by hand.

    1.4 database and statistical methods in Table 1 colon cancer risk factors single factor conditional logistic regression analysis results of questionnaire data input with epidata3.0 software using spss13.0 for statistical analysis, conditional logistic regression analysis using the maximum likelihood method stepwise selection variables introducing and removing variables significance level of 0.05 and 0.10, respectively.

    2 Results

    2.1 subjects general

    Case group and 142 patients, with an average age of 55.44 years old, the minimum age of 30, a maximum of 81 years, the male to female ratio was 1.6:1; 142 cases of the control group, an average of 55.25 years old, minimum 33 years, maximum 82 years, the male to female ratio of 1.6:1.

    2.2 single factor analysis results

    Each variable introduced conditional logistic regression model univariate analysis, the results showed that 31 variables, 13 variables difference was statistically significant. Regular exercise a high degree of culture, eat vegetables three factors of colon cancer protective factors, a high-fat diet, appendicitis history 10 factors for colon cancer risk factors, see Table 1.

    2.3 Multi-factor analysis

    Univariate analysis 13 variables into meaningful conditional logistic regression model, the six factors ultimately into the regression equation. Five variables colon cancer risk factors, often in a sitting position, respectively, a high-fat diet, history of gallbladder disease, appendicitis history, as well as first-degree relatives of cancer history; eat vegetables for colon cancer protective factors are shown in Table 2.

    3 Discussion

    The 3.1 fresh vegetables intake

    The results of this study show that eat the vegetables are protective factors of colon cancer, OR = 0.585 (95% CI: 0.131 to 0.824). Vegetables contain large amounts of dietary fiber, dietary fiber, resistant to digestive enzyme degradation in vivo, so that the fecal increase the amount of dilution carcinogens in the colon. While adsorption of bile salts, and bile salts is colorectal accelerator. Further glycolysis in dietary fiber can be bacteria produce short chain fatty acids lower the pH, and is not conducive to the growth of cancer cells. Sheila A Bingham et al [3] cohort study of the population of European countries and Ulrike Peters et al [4] have shown that dietary fiber and colon cancer case-control study of a number of cities in the United States was negatively correlated. Multivariate conditional logistic regression analysis results in Table 2 colon cancer risk factors

    Vegetables also contain a lot of vitamins, such as folic acid, vitamin C, and so on. L JOSEPH SU et al [5] and Qinting Jiang MS [6] studies have shown that folic acid is protective factors for colon cancer, F. Levi et al [7] studies have shown that vitamin C is protective factors for colorectal. In recent years, studies have shown that folic acid has antioxidant, inhibiting the role of oncogene activation. Vitamin C is important in the process of biological oxidation hydrogen delivery body, involved in the body to a variety of important metabolic, and can promote the formation of collagen tissue. It also detoxification, to promote cholesterol metabolism.

    3.2 high-fat diet

    Animal oil contains large amounts of fat, long-term high-fat diet, will be discharged into the increase in intestinal bile to help digest and absorb. Bile into the intestine intestinal bacteria break down into two bile acid, while secondary bile acid is a highly carcinogens carcinogens perennial role in the intestinal mucosa, may make the irritation of the intestinal mucosa cancer. The results of this study show that the consumption of animal oil-based is a risk factor for colon cancer, OR = 2.401 (95% CI: 1.314 ~ 6.265), consistent with the findings of domestic Chen Kun [8].

    3.3 seat

    The results of this study show that often in a sitting position status is a risk factor for colon cancer, OR = 1.814 (95% CI: 1.187 to 3.089). In the sitting state for a long period of time, the lack of effective activity of the body, the food residue, endogenous secretions (cholic acid) and the carcinogenic substances in the intestines residence time will be extended, thereby increasing the risk of colon prevalence.

    3.4 gallbladder disease

    Gallbladder disease in patients with bile acids in the intestinal the hepatic circulation rate may accelerate to bile acids in the intestinal exposure and the increased absorption of secondary bile acids with strong oxidation destruction of cellular genes reduced ability of the cells resist damage and malignant transformation. The results of this study show that the history of gallbladder disease is a risk factor for colon cancer, OR = 2.878 (95% CI: 1.348 ~ 6.678), consistent with such as Yue positive learning [9] findings.

    3.5 appendicitis

    The results of this study show that appendicitis history of colon cancer risk factors, OR = 3.034 (95% CI: 1.413 ~ 8.327), consistent with the results of Chen Kun, etc. [10] A retrospective cohort study. Appendicitis history of colon cancer relationship may be explained that the appendix is ​​an important immune organ, contains a wealth of lymphocytes plays an important role, especially in the female colon cancer immunity. Appendicitis or appendectomy after removal of the appendix immune function diminished or disappeared, they derived immune proteins reduce, the enterovirus defense against cancer-causing diminished capacity, resulting in the increase in the incidence of colon cancer.

    3.6 first-degree relatives of cancer history

    People with a family history of cancer than the general population are more likely to have cancer susceptibility gene of colorectal tumors in familial adenomatous polyposis (FAP) and hereditary non-polyposis colorectal cancer (HNPCC) genetic explicitly, the adenomatous polyposis coli (APC) gene and mismatch repair genes (MMR) gene mutations [11]. The results of this study show that the history of first-degree relatives of cancer is a risk factor for colon cancer, OR = 5.320 (95% CI: 1.314 ~ 6.265), consistent with Kari Hemminki et al [12] cohort study results.

    In summary, the studies suggest that the incidence of colon cancer may be associated with life eating habits, digestive disease history, and family history of cancer, and other factors related to. Therefore, to maintain good eating habits of life, active and effective in the treatment of diseases of the digestive system, and carry out regular checks on people with a family history of cancer, will be an important measure for the prevention of colon cancer.