Objective To study the prevalence,risk factors of overactive bladder (OAB) in middle-aged and senior residents in Zhengzhou China.Methods A randomized,community-based,crosssectional study was performed on 10 160 residents aged 40 or older in urban area of Zhengzhou by using a stratified system sampling approach.A questionnaire including the subjects' basic information,previous history,present history,the Chinese overactive bladder symptom score (OABSS) was filled on site.The diagnostic criteria for OAB was 'an urgency score for Question 3 of 2 or more,and an OABSS of 3 or more'.Chisquare test was used to determine the differences of prevalence between genders,age groups,BMI and people with and without diabetes mellitus (DM).A pairwise comparison was conducted between different age,BMI group by using Bonferroni method.Results A total of 10 160 residents were investigated and finally 9805 (96.5％) were qualified for final statistical analysis.The mean age was (57.9 ± 9.7) years.The overall prevalence of OAB was 2.1％ (209/9805),of which,with OABdry 1.0％,and OABwet 1.1％.Male subjects were more likely suffered from OAB than female,with 2.7％ (84/3129) versus 1.9％ (125/6676).The prevalence of OAB in both male and female increased with age.There was no significant difference in the prevalence of male and female before the age of 60 years (1.2％ versus 1.4％,P ＞ 0.05) and more common in men than in women after the age of 60 years (4.6％ versus 2.6％,P ＜ 0.05).The prevalence of the subjects with DM was significantly higher than those without DM (P ＜ 0.05).The subjects with BMIs of 30 or more were nore likely to have OAB (3.2％ versus 1.8％,P ＜ 0.05).Conclusions The prevalence of OAB increases with advancing age.The prevalence of male is higher than female after the age of 60 years.The diabetics and obese people are more likely to have OAB.