Multivariate logistic regression analysis revealed that , after adjusting for gender , body mass index , abdominal compression , position change , insertion time to cecum , and length of scope at cecum , only WE was significantly associated with painless insertion compared with AI ( odds ratio ( OR ) = @ , @ % confidence interval ( CI ) = @-@ @ , P < @ ) or WI ( OR = @ , @ % CI = @-@ @ , P < @ ) .