Trends in Sexual Risk Behaviors Among High School Students -- United States, 1991-1997

Each year, approximately three million cases of sexually transmitted diseases (STDs) occur among teenagers (1), and approximately one million become pregnant (2). Human immunodeficiency virus (HIV) infection is the sixth leading cause of death among persons aged 15-24 years in the United States (3). Unprotected sexual intercourse and multiple sex partners place young persons at risk for HIV infection, other STDs, and pregnancy. To determine trends in sexual risk behaviors among high school students, CDC analyzed data from the Youth Risk Behavior Survey (YRBS) for the years 1991, 1993, 1995, and 1997. This report summarizes the results of this analysis, which indicate that, from 1991 to 1997, the percentage of U.S. high school students who had ever had sexual intercourse decreased, and the prevalence of condom use among currently sexually active students increased.

The YRBS, a component of CDC's Youth Risk Behavior Surveillance System, measures the prevalence of health-risk behaviors among adolescents through representative national, state, and local surveys conducted biennially. The 1991, 1993, 1995, and 1997 national surveys used independent, three-stage cluster sampling to obtain representative cross-sectional samples of students in grades 9-12 in the 50 states and the District of Columbia. In 1991, 1993, 1995, and 1997, the sample sizes were 12,272, 16,296, 10,904, and 16,262, respectively; school response rates were 75%, 78%, 70%, and 79%, respectively; student response rates were 90%, 90%, 86%, and 87%, respectively; and overall response rates were 68%, 70%, 60%, and 69%, respectively.

For each of the four cross-sectional surveys, students completed a self-administered questionnaire that included questions about sexual intercourse, number of sex partners, and condom use. The wording of these questions was identical in each biennial survey. Sexual experience was defined as ever having had sexual intercourse, multiple sex partners as having had four or more sex partners during one's lifetime, current sexual activity as having had sexual intercourse during the 3 months preceding the survey, and condom use as having used a condom at last sexual intercourse among currently sexually active students. Data are presented only for non-Hispanic black, non-Hispanic white, and Hispanic students because the numbers of students from other racial/ethnic groups were too small for meaningful analysis.

Data were weighted to provide national estimates, and SUDAAN was used to calculate 95% confidence intervals and to conduct trend analyses. The relative percent change in behavior from 1991 to 1997 was calculated as the 1997 prevalence minus the 1991 prevalence divided by the 1991 prevalence and multiplied by 100. Secular trends were analyzed by using logistic regression analyses that controlled for sex, grade, and race/ethnicity and simultaneously assessed linear, higher order (i.e., quadratic and cubic), and overall time effects. Additional logistic regression models included significant time effects and their interactions with sex, grade, and race/ethnicity. For interactions that were significant (p less than 0.05), posthoc analyses were used to examine subgroup differences.

Compared with 1991, the prevalence of sexual experience in 1997 decreased 11%. Logistic regression analysis indicated a significant linear decrease overall and among male students and white and black students (p less than or equal to 0.01; Table_1). Among male students, sexual experience decreased 15% (from 57.4% to 48.8%); sexual experience among female students did not show a significant linear decrease. Sexual experience decreased 13% (from 50.0% to 43.6%) among white students and 11% (from 81.4% to 72.6%) among black students; sexual experience among Hispanic students did not show a significant linear decrease.

The prevalence of multiple sex partners decreased significantly overall (14%) (from 18.7% to 16.0%) and among male students (p less than 0.01; Table_1). The prevalence of multiple sex partners among male students decreased 25% (from 23.4% to 17.6%); multiple sex partners among female students did not show a significant linear decrease. The overall trend did not differ among grade or racial/ethnic subgroups.

The proportion of students who reported current sexual activity did not change significantly over time. Among currently sexually active students, condom use increased 23%, a significant linear increase (p less than or equal to 0.001; Table_1). The overall trend in condom use did not differ among sex, grade, or racial/ethnic subgroups.

Reported by: Div of Adolescent and School Health and Div of Reproductive Health, National Center for Chronic Disease Prevention and Health Promotion; Div of HIV/AIDS Prevention-Intervention, Research, and Support, Div of HIV/AIDS Prevention-Surveillance and Epidemiology, and Div of Sexually Transmitted Diseases Prevention, National Center for HIV, STD, and TB Prevention, CDC.

Editorial Note

Editorial Note: The findings in this report indicate that fewer high school students are engaging in behaviors that place them at risk for HIV infection, other STDs, and pregnancy. The decrease in sexual experience represents a reversal of the increasing trend in sexual intercourse rates among adolescents that occurred during the 1970s and 1980s (4).

These survey findings are consistent with other national data that have shown stable rates of sexual experience and increasing use of condoms among adolescents during the 1990s (4,5). These behavioral changes also are consistent with recent reports describing national decreases in related health outcomes among adolescents. During 1993-1996, gonorrhea rates decreased 35% among males and 11% among females aged 15-19 years (6). During 1992-1995, pregnancy rates among females aged 15-19 years declined in all 43 states with available data (7). The decrease in sexual risk behaviors among high school students during 1991-1997 also corresponds to an increase in the percentage of high school students who received HIV/AIDS education in school (from 83.3% in 1991 to 91.5% in 1997) (CDC, unpublished data, 1998).

The findings in this report are subject to at least three limitations. First, these data apply only to adolescents who attend high school. In 1996, 5% of persons aged 14-17 years were not enrolled in school (8). These adolescents are more likely to be sexually experienced and to have had multiple sex partners than those adolescents who are enrolled in school (9). Second, the extent of underreporting or overreporting cannot be determined, although the survey questions demonstrate good test-retest reliability (10). Finally, the survey provides no information on socioeconomic status and other variables that might explain subgroup differences.

The decreases in sexual risk behaviors and the corresponding improvements in reproductive health outcomes among adolescents are the result of broad efforts by parents and families; schools; community-based organizations; the religious community; the media; federal, state, and local government agencies; and adolescents. The dual approach of delaying first intercourse among all adolescents and increasing condom use among those who are sexually active has succeeded in reducing overall risk through improvements in both behaviors. Despite these findings, decreases in sexual experience and multiple sex partners were not found among all subgroups of students, and the percentage of currently sexually active students remained stable. Many adolescents remain at risk for HIV, other STDs, and unintended pregnancy. Expanded efforts are required of families, schools, and other social institutions that affect adolescents to achieve continued reductions in risk.

References

1. Institute of Medicine. The hidden epidemic. Washington, DC: National Academy Press, 1997.

2. Alan Guttmacher Institute. Sex and America's teenagers. New York, New York, and Washington, DC: The Alan Guttmacher Institute, 1994.

3. National Center for Health Statistics. Report of final mortality statistics, 1995. Hyattsville, Maryland: US Department of Health and Human Services, Public Health Service, CDC, 1997. (Monthly vital statistics report; vol 45, no. 1, suppl 2).

4. Ventura SJ, Curtin SC, Mathews TJ. Teenage births in the United States: national and state trends, 1990-1996. Hyattsville, Maryland: US Department of Health and Human Services, CDC, 1998.

5. Abma J, Chandra A, Mosher W, Peterson L, Piccinino L. Fertility, family planning, and women's health: new data from the 1995 National Survey of Family Growth. Vital Health Stat 1997;23:1-114.

6. CDC. Sexually transmitted disease surveillance, 1996. Atlanta: US Department of Health and Human Services, Public Health Service, 1997.

7. CDC. State-specific pregnancy rates among adolescents--United States, 1992-1995. MMWR 1998;47:497-504.

8. National Center for Education Statistics. Digest of education statistics, 1997. Washington, DC: US Department of Education, 1997.

9. CDC. Health risk behaviors among adolescents who do and do not attend school -- United States, 1992. MMWR 1994;43:129-32.

10. Brener ND, Collins JL, Kann L, Warren CW, Williams BI. Reliability of the Youth Risk Behavior Survey questionnaire. Am J Epidemiol 1995;141: 575-80.

TABLE 1. Percentage of high school students who reported sexual risk behaviors, by
sex, grade, race/ethnicity, and survey year -- United States, Youth Risk Behavior
Survey, 1991, 1993, 1995, 1997
=================================================================================================================
                                                      Four or more sex                          Condom use
                                   Ever had sexual     partners during  Currently sexually  during last sexual
                                     intercourse          lifetime            active*          intercourse+
                          Survey   ----------------   ----------------  ------------------  ------------------
                           year      %    (95% CI&)      %    (95% CI)      %    (95% CI)      %     (95% CI)
---------------------------------------------------------------------------------------------------------------
Sex
  Male                     1991    57.4    (+/-4.1)    23.4   (+/-3.0)    36.8   (+/-3.4)    54.5   (+/- 3.8)
                           1993    55.6    (+/-3.5)    22.3   (+/-2.7)    37.5   (+/-3.0)    59.2   (+/- 3.8)
                           1995    54.0    (+/-4.7)    20.9   (+/-2.6)    35.5   (+/-3.5)    60.5   (+/- 4.3)
                           1997    48.8    (+/-3.4)    17.6   (+/-1.5)    33.4   (+/-2.6)    62.5   (+/- 2.8)
  Female                   1991    50.8    (+/-4.0)    13.8   (+/-1.8)    38.2   (+/-3.4)    38.0   (+/- 4.3)
                           1993    50.2    (+/-2.5)    15.0   (+/-1.9)    37.5   (+/-1.8)    46.0   (+/- 2.8)
                           1995    52.1    (+/-5.0)    14.4   (+/-3.5)    40.4   (+/-4.2)    48.6   (+/- 5.2)
                           1997    47.7    (+/-3.7)    14.1   (+/-2.0)    36.5   (+/-2.7)    50.8   (+/- 3.0)

Grade
   9                       1991    39.0    (+/-5.0)    12.5   (+/-2.9)    22.4   (+/-3.9)    53.3   (+/- 6.2)
                           1993    37.7    (+/-4.2)    10.9   (+/-2.0)    24.8   (+/-3.2)    61.6   (+/- 5.7)
                           1995    36.9    (+/-5.9)    12.9   (+/-3.0)    23.6   (+/-4.0)    62.9   (+/- 5.5)
                           1997    38.0    (+/-3.8)    12.2   (+/-2.5)    24.2   (+/-3.3)    58.8   (+/- 5.6)
  10                       1991    48.2    (+/-5.7)    15.1   (+/-2.8)    33.2   (+/-4.6)    46.3   (+/- 4.7)
                           1993    46.1    (+/-3.6)    15.9   (+/-2.0)    30.1   (+/-3.0)    54.7   (+/- 4.5)
                           1995    48.0    (+/-5.1)    15.6   (+/-2.0)    33.7   (+/-3.1)    59.7   (+/- 4.6)
                           1997    42.5    (+/-4.3)    13.8   (+/-2.7)    29.2   (+/-2.9)    58.9   (+/- 3.6)
  11                       1991    62.4    (+/-3.2)    22.1   (+/-3.6)    43.3   (+/-3.6)    48.7   (+/- 5.8)
                           1993    57.5    (+/-3.5)    19.9   (+/-3.1)    40.0   (+/-3.6)    55.3   (+/- 3.0)
                           1995    58.6    (+/-5.0)    19.0   (+/-3.7)    42.4   (+/-4.4)    52.3   (+/- 6.2)
                           1997    49.7    (+/-5.2)    16.7   (+/-2.9)    37.8   (+/-4.8)    60.1   (+/- 5.2)
  12                       1991    66.7    (+/-4.4)    25.0   (+/-4.0)    50.6   (+/-4.5)    41.4   (+/- 3.6)
                           1993    68.3    (+/-4.6)    27.0   (+/-3.6)    53.0   (+/-3.9)    46.5   (+/- 4.0)
                           1995    66.4    (+/-4.0)    22.9   (+/-3.5)    49.7   (+/-3.9)    49.5   (+/- 4.4)
                           1997    60.9    (+/-6.5)    20.6   (+/-3.5)    46.0   (+/-5.0)    52.4   (+/- 3.5)

Race/Ethnicity @
  Non-Hispanic white       1991    50.0    (+/-3.2)    14.7   (+/-1.8)    33.9   (+/-2.8)    46.5   (+/- 4.6)
                           1993    48.4    (+/-2.8)    14.3   (+/-2.1)    34.0   (+/-2.1)    52.3   (+/- 3.9)
                           1995    48.9    (+/-5.0)    14.2   (+/-2.4)    34.8   (+/-3.9)    52.5   (+/- 4.0)
                           1997    43.6    (+/-4.2)    11.6   (+/-1.5)    32.0   (+/-3.1)    55.8   (+/- 2.0)
  Non-Hispanic black       1991    81.4    (+/-3.2)    43.1   (+/-3.5)    59.3   (+/-3.8)    48.0   (+/- 3.8)
                           1993    79.7    (+/-3.2)    42.7   (+/-3.8)    59.1   (+/-4.4)    56.5   (+/- 3.8)
                           1995    73.4    (+/-4.5)    35.6   (+/-4.4)    54.2   (+/-4.7)    66.1   (+/- 4.8)
                           1997    72.6    (+/-2.8)    38.5   (+/-3.6)    53.6   (+/-3.2)    64.0   (+/- 2.8)
  Hispanic                 1991    53.1    (+/-3.5)    16.8   (+/-2.6)    37.0   (+/-3.6)    37.4   (+/- 6.2)
                           1993    56.0    (+/-4.1)    18.6   (+/-3.1)    39.4   (+/-3.7)    46.1   (+/- 4.4)
                           1995    57.6    (+/-8.6)    17.6   (+/-3.7)    39.3   (+/-7.1)    44.4   (+/-11.1)
                           1997    52.2    (+/-3.6)    15.5   (+/-2.4)    35.4   (+/-3.9)    48.3   (+/- 5.6)

Total                      1991    54.1    (+/-3.5)    18.7   (+/-2.1)    37.4   (+/-3.1)    46.2   (+/- 3.3)
                           1993    53.0    (+/-2.7)    18.7   (+/-2.0)    37.5   (+/-2.1)    52.8   (+/- 2.7)
                           1995    53.1    (+/-4.5)    17.8   (+/-2.6)    37.9   (+/-3.4)    54.4   (+/- 3.5)
                           1997    48.4    (+/-3.1)    16.0   (+/-1.4)    34.8   (+/-2.2)    56.8   (+/- 1.6)
---------------------------------------------------------------------------------------------------------------
* Sexual intercourse during the 3 months preceding the survey.
+ Among currently sexually active students.
& Confidence interval.
@ Numbers of students in other racial/ethnic groups were too small for meaningful analysis.
=================================================================================================================

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