Population-based Case-control Study of Soyfood Intake and Breast Cancer Risk in Guangzhou Women

BACKGROUNDBreast cancer is a common malignant tumor, the vast majority of patients are women. Due to the difference of geographical environment, living habits and so on, the incidence reasons of breast cancer in different countries are many differences. Most of the countries in North America and Northern Europe are have a high incidence rate of breast cancer. Some of the countries in South America and southern Europe have a medium rate incidence of breast cancer, and most of Asia, Latin America and Africa region have a low incidence rate of breast cancer. Although incidence of women’s breast cancer in Asia is lower than that in the western countries’, the incidence of breast cancer shows significant growth trend, which makes breast cancer the first common malignant tumor among women. The first large-scale epidemiology research project of breast cancer in China was launched by the Chinese cancer foundation in2012. According to the research project’s results, onset age of breast cancer tends to be younger in our country, the incidence and death toll of breast cancer of Chinese female is rising. The incidence toll has increased to38.5%, and the death toll rose to37.1%,which brought very great influence to society and family. Women in Shanghai, Beijing, Tianjin and the coastal region of China are prone to have breast cancer, and especially in Shanghai. It is well known that the incidence of breast cancer is closely related to the activity of estrogen. Since 1991, the cancer research center of American first put forward that soybeans could reduce incidence of breast cancer, this thesis has been repeatedly demonstrated more than20years. The main reason is that the soy isoflavone which is the secondary metabolites of soybean has the same effect with estrogen. These studies have shown that the Asian women’s soy food intake is greater than which in the United States and Europe, which may be one of the differences of breast cancer incidence risk between eastern and western countries. There are different eating habits in different regions of our country. In view of the Guangzhou region, a very big difference in eating habits from north China, and soy intake is relatively small, and there is no report about the situation of soy isoflavone intake in Guangzhou and the relationship between soy isoflavone and breast cancer. To realize women’s actual situation of the soybean isoflavone intake in Guangzhou area and to explore its relationship with breast cancer carry out this topic research.OBJECTIVE1. To explore the women’s actual intake of soy products in Guangzhou, and discuss the influence factors of soy products intake according to investigation.2. Analysis of relationship people risk factors and breast cancer in Guangzhou women according to the case-control study.3. After adjustment the influence factors such as age, family history, lifestyle habits and analysis if there is a protective effect of soy isobflavones on breast cancer risk.4. Analysis of the effect of soy isoflavones on breast cancer risk in different periods, determine which period of intake of soy products which impact on breast cancer. Provide the basis for nursing health education, and guide the rational diet in susceptible people, so as to reduce the incidence of breast cancer of women.OBJECTS1. Case group sample selection①Inclusion criteria:a. The permanent residents in Guangzhou (Indigenous people in Guangzhou or residents who lived in Guangzhou for10years and above); b. The patients with firmed pathology diagnosis of primary breast cancer by the municipal leveled hospital in nearly more than1-2years; c. Before the reference date (date of diagnosis cases), there is no history of breast cancer; d. No history of cancer, tumours and mental illness.②exclusion criteria:a. The patients with non-primary breast cancer (inpatient for recurrence, metastasis or other complications); b. belong to Guangzhou household register but no occupants for a long time (≥10months) in Guangzhou.2. Control group sample selection①Inclusion criteria:In accordance with the principle of1:1paired, selection of Guangzhou residents (indigenous people in Guangzhou or people who lived in Guangzhou for10years and above), matching conditions for±5years old.②exclusion criteria:Has a history of cancer, or because of disease of endocrine system, benign breast disease and gynecological disease be in the hospital.METHODS1. Taken by the literature research and group discussion method designed three soy products food frequency questionnaires, including:hospital and household cases questionnaire, community control questionnaire.2. After a small-scale pre-test, revise and improve their own choice and prepared in the first part of soy products food frequency questionnaire (including general information、soy products food frequency questionnaire、home-entry--investigators to fill out form of the information associated with disease of the patients、Hospital--investigators to fill out form of the information associated with disease of the patients).3. By using convenience sampling method, a questionnaire surveys were conducted in Guangzhou healthy women in control group inclusion and exclusion criteria, and in breast cancer patients within the case inclusion and exclusion criteria more than2hospitals and community in Guangzhou region.STATISTICAL METHODGeneral data, after carefully examination, check the application SPSS19.0software entry. Excel2010is appiled to input intake frequency data of soy products and calculate. Statistical processing with descriptive statistics for case group and control group studies the composition structure of the object and soybean isoflavone intake and food sources for analysis. Different ages of soybean isoflavone intake and differences intake of between the two groups by paired t-est analysis. Using stepwise multiple regression analysis the influence factors of soybean isoflavone intake. According to single factor and multi-factor unconditioned logistic regression analysize the risk factors of breast cancer and the relationship between soy isoflavones and breast cancer. Using SPSS19.0software for statistical analysis.RESULTSFrom August2012to December2012, researchers in the mammary gland department of the two hospitals in Guangzhou and several communities and the old park to complete the case group and control group data collection work. The questionnaires were distributed and220were220valid questionnaires, recovery efficiency of100%. Among them200qualified questionnaires, effective rate was90.9%.1. Relationship between risk factors and breast cancerThe aged of respondents is from21to76years old, average aged of which is41.12±13.46years old. Wilcoxon results show that the two grouPs in age, body index, occupation, income, family status, breastfeeding time, moisture regain and menoPause age, oral contracePtive use and hormone rePlacement therapy, breast disease, family history of cancer, drinking, smoking, tastes, regular exercise, sleep time distribution, there is no statistical difference (P<0.05). people risk factors, a total of18entries, including layering process for the measurement data after single factor logistic regression analysis respectively, married (OR=5.07), has birth (OR=4.12),1～3children (OR=3.88), menarche age≥17year-old (OR=4.39) and passive smoking (OR=4.42) with a risk factor for breast cancer. Working (OR=0.33), earning>20000yuan (OR=0.39), physical condition common and good (OR=0.14,0.12), the sleep time≥7h (OR=0.18) with protective factors for breast cancer, the above results are statistically significant difference (P<0.05).2. Intake investigation of soybean isoflavone From the survey we found that women’s average daily intake of soy isoflavones in Guangzhou is23.56±22.31mg/d for nearly five years, adulthood is16.54±26.38mg/d, adolescence is12.71±26.69mg/d, juvenile stage is11.39±24.96mg/d. The major sources of the food for these women to get soybean isoflavone are homemade soy-bean milk, beancurd jelly, bean sprouts and soy tofu, they seldom eat deep-fried bean curd, low-sugar soybean milk powder, bean curd sticks, fried bean curd sticks, edamame and vegetarian duck/soy chicken in case group women. The differences of average daily intake of soy isoflavones during nearly five years, between adolescence and young adulthood were statistically significant difference (P<0.05). Average daily intake of soy isoflavones during nearly five years is higher than other age groups of average daily intake. The major sources food for soybean isoflavone are bean sprouts, beancurd jelly, soy tofu, homemade soy-bean milk, almost don’t eat beancurd puff, deep-fried bean curd, bean curd sticks, fried bean curd sticks, vegetarian duck/soy chicken in control group women. Average daily intake of soy isoflavones differences between different age groups were statistically significant (P <0.05), and the average daily intake of soy isoflavones in nearly five years> adulthood average daily intake of soy isoflavones> adolescence average daily intake of soy isoflavones> infancy average daily intake of soy isoflavones. Two groups of four ages average daily intake of soy isoflavones in nearly five years intake differences had statistical significance (P<0.05). All the factors of the single factor analysis as independent variables and all ages average daily intake as a dependent variable is established in multiple regression model. Concluded that the main factors influencing the soybean isoflavone intake nearly five years is sleep time (t=0.429, P <0.001).3. Soy isoflavones relations with breast cancerAdulthood control women average daily intake of soy isoflavones (P25=12.300, P50=21.300, P75=34.480) is significantly higher than cases (P25=6.800, P5o=12.525, P75=226.758), and found that adulthood soy isoflavones intake is associated with breast cancer, the OR value is0.981(0.967-0.995), there is statistical significance difference (P<0.05). Soy isoflavones intake in recent five years women in Guangzhou region is the protection factor in breast cancer, and no found intake of soy isoflavones in other age groups is associated with breast cancer.4. Relationship between risk factors, soy isoflavones and breast cancerStatistically significant covariates in conditional logistic regression analysis model of the single factor, introduce to the various factors of unconditioned logistic regression analysis model for multifactor statistical analysis, conclude that fertility status, health status, smoking, sleep time is confounding factors, after rule out the impact of these confounding factors, is still showing the amount of nearly five years, average daily intake of soy isoflavones≥17.075mg/d are protective factors for breast cancer, the OR value<1, there is statistical significance (P<0.05). Four confounders in nearly five years average daily intake of soy isoflavones as the independent variable at the same time, the breast cancer as the dependent variable for binary classification unconditioned logistic regression analysis, obtained nearly five years, average daily intake of soy isoflavones content≥17.075mg/d is the protection factor in breast cancer.CONCLUSION1. Breast cancer risk factors and protective factorsIt is well known that early menarche age (12years old or less) is a risk factor for breast cancer, in combination with the results of this study, the menarche age too early and too late may increase the risk of breast cancer. High yield (>3times) and breast cancer are not found in the relationship, which indicates that high fertility without the risk of breast cancer. In clinical guide vulnerable groups to avoid smoking and passive smoking, pay attention to rest more, assure enough sleep time, pay attention to their health.2. Lower average daily intake of soy isoflavonesWomen in Guangzhou have a relatively low average daily intake of soy isoflavones, what’s more adult intake was higher than the juvenile intake, and women in Guangzhou region of soybean isoflavones is relatively single food source. In nursing, nutrition and health education on patients and family members should be strengthened, reasonable collocation soy diet, advocate a healthy and diversification diet.3. Soy isoflavone intake can reduce the risk of breast cancerNearly five years in guangzhou women average daily intake of soy isoflavones≥17.075mg/d is the protection factor in breast cancer, which can provide the basis for the clinical health education of susceptible population, guide the rational diet of healthy women, and reduce the incidence of breast cancer.