Primary Exposure
In the “sexual behavior” questionnaire, men were asked by” ever had vaginal sex with a woman”, ”ever had oral sex with a woman”, ”ever had anal sex with a woman”, ”ever had any sex w/man: anal, oral”, and women were asked by ”ever had vaginal sex with a man”, ”ever had oral sex on a man”, ”ever had anal sex with a man”, ”ever had any kind of sex w/woman”. Based on the sexual behavior of the population, we categorized individuals into two groups: sexual identity and sexual type. The sexual identity group comprised individuals with no sex, heterosexual, homosexual, bisexual, or unclear. The sexual type group consisted of individuals with no sex, heterosexual vaginal sex, heterosexual oral sex, heterosexual anal sex, heterosexual multiple types, bisexual sex, male homosexual sex, female homosexual sex, or unclear.