送交者: Fuzzlogic 于 2005-7-12, 19:11:40:
Jeffrey Bednarski MD, PhD
Edited by Katie Plax MD
Despite recent decreases, the United States continues to have higher rates of unintended pregnancy, abortion and sexually transmitted infections (STIs) in comparison to other developed countries around the world. In response to this discrepancy, numerous federal, state and local programs have been initiated to affect positive changes in adolescent sexual behaviors. In fact, one of the 10 leading national health objectives set for 2010 (Healthy People 2010) is to increase sexual responsibility among teens. This responsibility is defined as the following: an increase in the proportion of adolescents who have never had sex, among those who have had intercourse to have abstained in the last 3 months, and to increase the numbers of teens who use condoms if sexually active.
Two large national studies have recently reported on the changing landscape of adolescent sexual behaviors. The Youth Risk Behavior Surveillance 2003 surveyed about 15,000 high school students (grades 9-12, ages 15-17) across the country. The National Survey of Family Growth conducted home interviews of approximately 20,000 adolescents. Both of these studies (and several others) demonstrated similar findings: teenage sexual experience decreased and protective behaviors increased.
The percentage of female adolescents who had ever had sexual intercourse decreased from 51% in 1988 to 46% in 2002. A similar change was observed for sexually experienced adolescent males with a decline from 60% in 1988 to 46% in 2002. Collectively, these changes represent a 16% decrease in sexual experience among high school students. These downward trends are significant changes from the marked and continual increases in sexual activity in the 1970s and 1980s.
Current sexual activity has been defined as intercourse in the 3 months prior to the survey. Importantly, there was no change in the percentage of teens who were sexually active. Between 1991 and 2001, between 33-40% of females and between 33-38% of males were sexually active.
While there was no change in the proportion of sexually active adolescents there were significant changes in other risk factors, such as number of partners and condom use. Intercourse with multiple partners has been used as an indicator for heightened risk for STIs. From 1991 to 2001 there was a 24% overall decrease in the prevalence of high school students who had 4 or more partners. Interestingly, this change was solely manifested as a decrease in males with multiple sex partners. There was no change over the time period in the percentage of females who had multiple sex partners. Another important risk factor for STIs and pregnancy is the use of condoms. The percentage of sexually active teens who used a condom at last intercourse increased from 1991 to 2001 in both males (55% to 69%) and females (38% to 57%). Also, a substantial increase in condom use at first intercourse was observed in both genders from 1988 to 1995: 55% to 69% for males and 50% to 70% for females.
Collectively, these statistics demonstrate that adolescents are exhibiting more responsible sexual behaviors with an increase in abstinence, a decrease in the number of sexual partners and an increase in contraceptive use. Concomitant with these changes in sexual practices, changes in the pregnancy rates and the incidence of STIs among adolescents have been documented. The teen pregnancy rate in the U.S. declined from 116 per 1000 females in 1991 to 84.5 per 1000 females in 2000. Furthermore, the U.S. teen birth rate decreased by 30% from 62 per 1000 females in 1991 to 43 per 1000 females in 2002. With respect to STIs, a steady decline in the incidence of gonorrhea and syphilis has been reported through the 1990s and early 2000s. The numbers of new AIDS and HIV cases has not changed and the incidence of herpes infections appears to have increased.
In a recent statistical analysis Santelli et al. demonstrated that the decline in teenage pregnancy rates could be attributed equally to the decrease in sexual experience (53%) and to improved contraceptive use (47%). However, instruction on sex and birth control to adolescents shows a marked disparity. The majority of teens report formal instruction before age 18 on how to say no to sex (86% of females and 83% of males) and about 2/3 of these adolescents had received the information prior to the start of high school. However, only 2/3 of teens (both male and female) had received formal education on contraceptive use prior to age 18; and less than 50% of teens had received contraceptive instruction before high school.
Progress has been made in improving adolescent sexual responsibility. However, further improvements are still needed. Despite recent declines, the United States continues to have a teen birth rate amongst the highest in developed countries in the world and nearly 1/2 of the 19 million new cases of STIs in 2000 were among persons aged 15-24. Furthermore, the national health objective for 2010 is to increase to 95% the proportion of high school adolescents who have never had sex, have not been sexually active in the last 3 months, or have used a condom at their last sexual encounter in the last 3 months. In 2001, 86% of teens achieved this goal compared to 80% in 1991. Additional education programs are necessary to continue to improve adolescent sexual behaviors. These programs need to not only focus on abstinence but also on options for and proper use of contraceptive techniques.
References:
Abma, J., Martinez, G., Mosher, W. and Dawson, B. (2004). Teenagers in the United States: sexual activity, contraceptive use, and childbearing, 2002. Vital Health Stat 23: 1-48.
Biddlecom, A. (2004). Trends in sexual behaviors and infections among young people in the United States. Sex Transm Infect 80: ii74-79.
Brener, N., Lowry, R., Kann, L., Kolbe, L., Lehnherr, J., Janssen, R. and Jaffe, H. (2002). Trends in sexual risk behaviors among high school students -- United State, 1991-2001. MMWR Morb Mortal Wkly Rep 51: 856-859.
Grunbaum, J., Kann, L., Kinchen, S., Ross, J., Hawkins, J., Lowry, R., Harris, W., McManus, T., Chyen, D. and Collins, J. (2004). Youth risk behavior surveillance -- United States, 2003. MMWR Surveill Summ 53: 1-96.
Santelli, J., Abma, J., Ventura, S., Lindberg, L., Morrow, B., Anderson, J., Lyss, S. and Hamilton, B. (2004). Can changes in sexual behaviors among high school students explain the decline in teen pregnancy rates in the 1990s? J Adolesc Health 35: 80-90.