From 638 households visited, there were 638 eligible participants. There were no deaf or illiterate persons among selected sample. Eight (1.3%) of the 638 eligible participants refused to participate, which yielded a final sample of 630; this met the enrollment target that had been obtained in the power analysis (see Methods). The refusal rates for individual questions were less than 6%. These rates were similar for males and females. The demographic distributions in terms of age group,gender and the urban–rural ratio of the selected participants and those of the total population aged 15– 44 years in Nakhonsawan were similar.