participants aged 18 to 69 years liveing in shandong province,who were without disability and mental disorders,were eligible to participate in the survey.we used complex,4-stage cluster sampling to select the participants. First,we selected 20 counties/districts from 140 counties and districts after stratification by geographic distribution and by residence status (figure 1). Second,using proportional probability sampling ,we selected 3 townships( in rural areas) or 2 streets(in urban areas) from each selected county/district.then, also using proportional probability sampling,we selected 3 villages(in rural areas) or neighborhoid communitied(in urban areas) from each sampled township (rural) or street(urban).finally , in each selected village and neighborhood community, we randomly selected 100 adults from the local residents list.A total of 15,600 participants aged 18 to 69 years were selected from 13,010 households among156 communities and villages.