Level of education (categorized as no schooling completed, elementary education, secondary education, or undergraduate degree) was reported by 426 (10.6%), 611 (15.2%), 939 (23.3%) and 2,058 (51.0%) participants, respectively, while 169 (4.0%) did not answer the question about education. Age and geographical regions of the study participants were comparable to the general population in Thailand (Table 1) [16]. However, we noted that study participants were more likely to be female, and had higher education than the general population in Thailand (both p