Chiao et al. BMC Public Health 2012, 12:527 http://www.biomedcentral.com/1471-2458/12/527 Table 2 Results from multivariate logistic regression models of predicting involvement in premarital sex by age 22, TYP (N=1,777) (Continued) Family structure Lives with both biological parents Others Perceived family support School work Yes No Yes No Yes No Yes No Yes No Yes No Economic difficulty Emotional difficulty Perceived friend support School work Economic difficulty Emotional difficulty 1.0 1.0 1.3 1.0 0.8 1.0 0.8 1.0 0.9 1.0 0.9 1.0 2.0* 1.0 (0.6-1.6) (0.8-2.0) (0.5-1.3) (0.5-1.2) (0.6-1.4) (0.6-1.4) (1.1-3.5) Page 8 of 10 0.7 1.0 1.1 1.0 1.1 1.0 0.8 1.0 1.0 1.1 1.0 0.8 1.0 (0.4-1.1) (0.7-1.9) (0.5-2.3) (0.5-1.2) (0.7-1.8) (0.4-1.6) 2.9* (1.3-6.6) Note: All logistic regression models adjust for sampling cluster; AOR represents adjusted odds ratios for sample cluster; CI represents confidence interval; }p < 0.10, *p < 0.05, **p < 0.01, ***p < 0.001. sex during college, regardless of gender. Premarital sex appears to be increasingly common in the romantic rela- tionships of the Taiwanese young populace [27]. Our results suggest a cultural shift regarding premarital sex- ual activity among Taiwanese college-age youth. The increased acceptance of more liberal and permissive sex- ual attitudes is associated with the increased likelihood of sexual activity among Taiwanese youth. It is recom- mended that future cigarette, alcohol and sexual risk materials developed for Taiwanese college students take these shifting social norms into consideration and pay special attention to gender specific measures. In addition, there are potentially serious health and so- cial implications for those engaging in premarital sex without protection such as use of condoms or other contraceptives to prevent unwanted pregnancy or sexu- ally transmitted diseases [37]. In fact, contraceptive use is not common among Taiwanese college students, al- though the proportion using contraceptives does in- crease by age [7]. In separate analyses, we found that less than half (43%) of college students who had pre- marital sex by age 20 reported consistent contraceptive use. Approximately half (52%) of college students who had premarital sex by age 22 self-reported consistent contraceptive use. Because premarital sex among college youth will likely become more prevalent, encouraging consistent contraceptive use should become a major point of emphasis for health professionals dealing with Taiwanese college students. As suggested by Social Learning Theory, peer group influence plays a significant role in cigarette smoking, al- cohol use, and premarital sex among college students. Our results partly supported that respondents’ percep- tions of their close friends’ risky behaviors (cigarette smoking, alcohol use and sexual activity) were higher among youth who were sexually active by age 20 than those who were sexually abstinent. Even when control- ling for adolescent risky health behaviors, multivariate analyses in Model 2 showed later premarital sex (by age 22) was positively associated with perceived close friends’ sexual behavior [8,19,36]. In contrast, the non- significant predictive effect of perceived cigarette smok- ing of best friends for males and non-significant predict- ive effect of perceived alcohol use of best friends for