背景：青少年早齡從事性交行為，可預測其青少年期，甚至成年期的負向生活經驗，包括學業成績較差、教育達成的水準較低、從事危險性行為(多重性伴侶、性交次數頻繁、不使用避孕措施)，及其衍生的非預期懷孕、感染愛滋病或其他性傳染疾病。目前為止，國內對於影響青少年早齡從事性交行為及避孕使用的危險及保護因子仍缺乏足夠的瞭解。
目的：針對學校同儕和家庭因素，尋找與青少年初次性交年齡及避孕使用有關的保護因子及危險因子。
研究設計：二手資料分析。
研究對象：資料來自國民健康局2000年台灣地區在校學生性知識態度行為研究調查。以調查完訪的8541人為研究母群，篩選15-19歲就讀高中、高職、五專的青少年共7721人為研究對象。
主要測量變項及統計方法：依變項有二：第一為是否發生過性經驗，並考慮初次性經驗的年齡；第二為初次性經驗時有沒有避孕。自變項除了學校同儕和家庭因素，尚包括社會經濟整體特徵及個人因素的測量。以Cox’s proportional hazard regression估計學校同儕和家庭因素與初次性交年齡及避孕使用之相關性。1990-1995年17個縣市社會經濟指標統計來自內政部調查資料。
結果：有10.1%的男生及8.7%的女生表示曾與異性有過性交行為，男生發生第一次性交年齡以16歲的比例佔最多(31%)；女生則是17歲(32%)。不管是男生或女生在初次性交時僅大約四成有使用避孕措施，女生以45%略高於男生的41 %。在同時考慮社會經濟整體特徵因素、學校同儕因素、家庭因素、及個人因素之多變項分析結果顯示，男生與增加早齡性交風險有關的危險因子包括就讀私立學校(風險比[Hazard Ratio: HR]=1.35，95% CI：1.02-1.79)、不希望再繼續升學(HR=1.62， 95% CI：1.07-2.43)、同儕大多數有性經驗(HR=7.73，95% CI：4.72-12.7)、同儕少數有性經驗(HR=3.30，95% CI：2.16-5.05)、親子曾詳細討論如何與異性交往(HR=1.51，95% CI：1.11-2.06)、親子曾詳細討論婚前性交的後果(HR=2.41，95% CI：1.48-3.94)、親子曾詳細討論夢遺、月經或手淫(HR=2.28，95% CI：1.18-4.38)、父母贊成婚前性行為(HR=1.79，95% CI：1.14-2.81)；而親子曾約略談過性病或愛滋病(HR=0.57，95% CI：0.39-0.83)則是保護因子，會延緩初次性交的發生。在女生方面，危險因子為就讀私立學校(HR=1.61，95% CI：1.16-2.22)、男性好友贊成婚前性行為(HR=1.75，95% CI：1.28-2.38)、同儕大多數有性經驗(HR=4.02，95% CI：2.53-6.37)、同儕少數有性經驗(HR=2.42，95% CI：1.72-3.40)、親子曾詳細討論性交的後果(HR=1.39，95% CI：1.05-1.85)、親子曾詳細討論如何避孕(HR=2.46，95% CI：1.14-5.31)、親子曾詳細討論戀愛或擇偶、(HR=2.85，95% CI：1.79-4.55)、親子曾約略討論戀愛或擇偶(HR=1.71，95% CI：1.23-2.38)；保護因子則為就讀高中(HR=0.49，95% CI：0.35-0.68)或高職(HR=0.61，95% CI：0.44-0.84)、與父親關係很好(HR=0.59，95% CI：0.39-0.90)、和母親相處時間較多(HR=0.60，95% CI：0.40-0.91)、親子曾約略討論生殖生理或懷孕(HR=0.66，95% CI：0.46-0.94)。在初次性交的避孕使用方面，男生的家人關愛程度很高(Z-統計量=3.02，p-value<0.001)、或還算關愛(Z-統計量=2.95，p-value <0.001)是保護因子，會增加初次性交時使用避孕措施的可能性；女生的保護因子為父親的性態度中立(Z-統計量=2.01，p-value=0.04)。但是，女生與父親關係還可以(Z-統計量=-2.48，p-value=0.01)、親子曾詳細討論婚前性交的後果(Z-統計量=-2.89，p-value<0.01)則是危險因子，會增加初次性交時不使用避孕措施的風險。
結論：本研究分析結果符合Kirby針對青少年性行為所提出之社會規範-連結理論。台灣青少年初次性交年齡，明顯受學校同儕和父母所認同的規範，以及與同儕、父母連結程度的影響。因此，未來學校和家庭除了給予青少年正確性教育的實質內容外，也應強化與青少年在可接受的性行為規範上的連結。而青少年醫療保健政策及青少年懷孕/生育介入計畫則可以針對本研究中所發現之相關因素擬定防治策略。

Background: Teenagers who had first sexual intercourse early could be expected to have more negative life experiences in adolescence as well as in adulthood, including poorer academic performance, lower educational levels, more risky sexual behaviors (multiple sex partners, had frequent intercourse, less contraceptive use), and involved in unintended pregnancy, HIV and other sexual transmitted diseases. There is limited understanding so far of the risk and protective factors associated with early initiation of sex and contraceptive use among our teenagers.
Objective: To identify the risk and protective factors in regard to peer influence and family characteristics for the age at the first sexual intercourse and contraceptive use.
Design: Secondary data analysis.
Participants: The data were obtained from a high school survey of sexual knowledge, attitude and behavior conducted by the Bureau of Health Promotion in 2000. Based on the initial sample of 8541 teenagers, a total of 7721 teenagers aged 15-19 who studied in regular, alternative high schools and 5 year vocational schools were included in our final analysis.
Main Outcome Measures and Statistical method: Two outcome variables were assessed in this study: age of first sexual intercourse and contraceptive use at the first sexual intercourse. Independent variables included measures of peer, family, social context, and individual characteristics. The relationship of peer and family factors to age at first sexual intercourse and contraceptive use was estimated by the Cox's proportional hazard regression. Socio-economic indicators of the 17 cities and counties from 1990-1995 were retrieved from the Ministry if Internal Affairs,
Results: 10.1% of boys and 8.7% of girls were sexually experienced. The boys who had their first sex at age 16 consisted of the biggest proportion, 31%, among sexually experienced ones and girls had the biggest proportion (32%) at age 17. Percent of contraceptive use at the first sexual intercourse was 45% for boys and 41% for girls. The multivariate analyses which included social and economic contextual variables, peer, family, and individual characteristics revealed the significant risk factors for the age at the debut of sexual intercourse were studying in the private high schools (Hazard Ratio=1.35, 95% CI：1.02-1.79), having no aspiration for higher education (HR=1.62, 95% CI：1.07-2.43), having friends who were sexually experienced (HR=7.73, 95% CI：4.72-12.7 for many versus none ; HR=3.30, 95% CI：2.16-5.05 for little versus none), having discussions with parents regarding intimate relationships between opposite sexes (HR=1.51, 95% CI：1.11-2.06), having discussions regarding the consequences associated with premarital sex (HR=2.41, 95% CI：1.48-3.94), having discussions regarding seminal emission, menarche or masturbation (HR=2.28, 95% CI：1.18-4.38), parental open attitudes towards premarital sex (HR=1.79；95% CI：1.14-2.81). On the other hand, having discussions with parents regarding venereal disease or AIDS roughly was a protective factor (HR=0.57, 95% CI：0.39-0.83). Among girls, risk factors were studying in the private high schools (HR=1.61, 95% CI：1.16-2.22), having male partners who consented to premarital sex (HR=1.75, 95% CI：1.28-2.38), having friends who were sexually experienced (HR=4.02,95% CI：2.53-6.37 for many versus none ; HR=2.42；95% CI：1.72-3.40 for little versus none), having discussions regarding the consequences of sexual intercourse (HR=1.39, 95% CI：1.05-1.85), having discussions regarding contraception (HR=2.46, 95% CI：1.14-5.31), having discussions regarding the love between opposite sexes or the choice of a spouse (HR=2.85, 95% CI：1.79-4.55 for frequently versus none; HR=1.71, 95% CI：1.23-2.38 for occasionally versus none). Protective factors were studying in regular (HR=0.49, 95% CI：0.35-0.68) or alternative high schools (HR=0.61, 95% CI：0.44-0.84) as compared to studying in 5 year vocational schools, good relationship with their fathers (HR=0.59, 95% CI：0.39-0.90), spending more time with their mothers (HR=0.60, 95% CI：0.40-0.91), having discussions regarding reproduction physiology or pregnancy (HR=0.66, 95% CI：0.46-0.94). In practicing contraception at the initiation of sexual intercourse, family caring (Z-statistics=3.02, p-value<0.001 for high versus low; Z-statistics==2.95；p-value <0.001 for moderate versus low) was a significant predictor for contraceptive use for boys. For girls, fathers’ neutral attitudes towards sex a significant predictor for contraceptive use (Z-statistics=2.01, p-value=0.04). However, fair relationships with their fathers (Z-statistics=-2.48, p-value=0.01), and having discussions regarding the consequences of premarital sex (Z-statistics=-2.89, p-value<0.01) could increase the risks of no contraceptive use at the first sexual intercourse.
Conclusions: Our analysis results were consistent with the theory of social norm-connectedness for adolescent sexual behaviors proposed by Dr. Kirby. The age at the first sexual intercourse was apparently influenced by the norms consented by the peers and parents, as well as the connectedness of teenagers to these norms. The school and family should not only provide correct sex education for our teenagers, but also strengthen their connectedness to the acceptable norms. Health policy for teenagers and intervention programs for prevention of adolescent pregnancy and childbearing could draft their plans based on our findings of the risk and protective factors for the age at the debut of sexual intercourse and contraceptive use at the time of the first sexual experience.

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