中文摘要：

目的探讨汉族大肠癌无症状平均风险人群中不同年龄组进展期肿瘤的发病率,从而为确定最佳的大肠癌筛查开始年龄提供科学依据。方法采用横断面研究设计,利用自制调查表对就诊于全国19家医院并接受结肠镜检查的大肠癌平均风险人群进行调查。调查内容包括人口学特征、生活方式、饮食习惯、肠镜检查结果等。基于之前已建立的平均风险人群大肠进展期肿瘤发生风险评分系统（由年龄、性别、吸烟、糖尿病、绿色蔬菜、腌制食品、油炸熏制食品、白肉等8个变量组成,总分为0～14分）对研究对象进行发生风险评估,计算各风险等级进展期肿瘤发病率。不同风险等级、不同年龄组、不同性别之间进展期肿瘤发病率比较采用χ^2检验。结果共7 541例患者完成全结肠镜检查。随着危险评分增加,进展期肿瘤发生率也明显升高。风险评估得分为0～2分的研究人群中,70岁以下的年龄组进展期肿瘤的发生率处于1.3%～4.0%的较低水平,70岁以上的年龄组进展期肿瘤的发生率处于8.9%～15.3%的较高水平,两组人群进展期肿瘤的发病风险差异有统计学意义（P〈0.01）;风险评估得分为3～4分的研究人群中,45岁以下的年龄组进展期肿瘤的发生率处于3.6%的较低水平,45岁以上的年龄组进展期肿瘤的发生率为5.4%～14.8%,两组人群进展期肿瘤的发病风险差异有统计学意义（P〈0.01）;风险评估得分为〉4分的研究人群中,进展期肿瘤发生率处于9.8%～22.7%的较高水平,其40～44岁年龄组进展期肿瘤的发生率（9.8%）高于风险评估得分为0～2分的研究人群中70～74岁年龄组（8.9%）。在研究总体人群中,55岁以下的年龄组进展期肿瘤的发生率处于2.9%～4.6%的较低水平,55岁以上的年龄组进展期肿瘤的发生率处于6.8%～17.6%的较高水平,两组人群进展期肿瘤的发病风险差异有统计学意义（P〈0.01）。?

英文摘要：

Objective To evaluate the prevalence of advanced colorectal neoplasm（ACN） in asymptomatic average-risk Chinese Han population,so as to provide a scientific basis for determining the optimal age for colorectal cancer screening.Methods A prospective cross-sectional design was used in this study.We used a self-made questionnaire to survey the average-risk adults receiving colonoscopy;the subjects were from 19 nationwide representative hospitals.The survey items included the demographic characteristics,life style,dietary habits,colonoscopy examination results,etc.The risk of ACN was evaluated using previously established average-risk evaluation system,which was composed of eight variables： age,sex,smoking,diabetes mellitus,green vegetables,pickled food,fried food and white meat,with a total score of 0 to 14 points.We calculated the ACN prevalence of each risk level.The χ^2-test was used to compare the prevalence rates of ACN between different risk levels,age groups and genders.Results A total of 7,541 subjects received complete colonoscopies.The ACN prevalence rose greatly with the increase of risk score.In the population with a risk score of 0-2,the ACN prevalence was 1.3%-4.0% in those younger than 70 years and 8.9%-15.3% in those elder than 70 years（P0.01）.In the population with a risk score of 3-4,the ACN prevalence was 3.6% in those younger than 45 years old and 5.4%-14.8% in those elder than 45 years（P0.01）.In the population with a risk score higher than 4,the ACN prevalence was at a high level（9.8%-22.7%）,with the prevalence being 9.8% in the 40-44 years group,which was higher than those in subjects of 70-74 years old with a risk score of 0-2（8.9%）.The overall ACN prevalence was 2.9%-4.6% in subjects younger than 55 years old and 6.8%-17.6% in those elder than 55 years（P0.01）.The high-risk age of ACN was elder than 45 in male and elder than 60 in female.Conclusion The optimal starting ages for colorectal cancer screening are different for subjects with different risks and genders.The