Trends in Human Immunodeficiency Virus-Related Risk Behaviors among High School Students-United States, 1991-2005

Article excerpt

Young persons who engage in unprotected sexual intercourse or use injection drugs are at increased risk for human immunodeficiency virus (HIV) infection. To examine changes in HIV-related risk behaviors among high school students in the United States during 19912005, the Centers for Disease Control and Prevention (CDC) analyzed data from 8 national Youth Risk Behavior Surveys (YRBS) conducted during that period. This report summarizes the results of that analysis. Measures aimed at changing these risk behaviors should be strengthened to decrease the incidence and prevalence of HIV/acquired immunodeficiency syndrome (AIDS) among young persons and meet the national 2010 objective for adolescent sexual behavior (objective 25-11). (1)

METHODS

Sample

The biennial national YRBS, a component of CDC's Youth Risk Behavior Surveillance System, used independent, 3-stage cluster samples for the 1991-2005 surveys to obtain cross-sectional data representative of public and private school students in grades 9-12 in all 50 states and the District of Columbia. Sample sizes ranged from 10,904 to 16,296. School response rates ranged from 70% to 81%, and student response rates ranged from 83% to 90%; overall response rates for the surveys ranged from 60% to 70%.

Procedure

For each cross-sectional national survey, students completed anonymous, self-administered questionnaires that included identically worded questions about sexual experience, number of sex partners, current sexual activity, condom use, and injection drug use. The YRBS questions were as follows: "Have you ever had sexual intercourse?" "During your life, with how many people have you had sexual intercourse?" "During the past 3 months, with how many people have you had sexual intercourse?" "The last time you had sexual intercourse, did you or your partner use a condom?" and "During your life, how many times have you used a needle to inject any illegal drug into your body?" The wording of the question on injection drug use changed substantially after the 1993 survey, so 1991 and 1993 data are not included in this report. Sexual experience was defined as ever having had sexual intercourse. The term "multiple sex partners" was defined as having 4 or more sex partners during the person's lifetime. Current sexual activity was defined as having sexual intercourse during the 3 months preceding the survey. Condom use was defined as use of a condom during last sexual intercourse among currently sexually active students. Beginning with the 1995 survey, injection drug use was defined as ever having used a needle to inject any illegal drug into the body. Race/ethnicity data are presented only for non-Hispanic black, non-Hispanic white, and Hispanic students (who might be of any race); the numbers of students from other racial/ethnic groups were too small for meaningful analysis.

Data Analysis

Data were weighted to provide national estimates, and the statistical software used for data analysis accounted for the complex sample design. Temporal changes were analyzed using logistic regression analyses, which controlled for sex, race/ethnicity, and grade and simultaneously assessed linear and quadratic time effects. (2) Quadratic trends indicate a statistically significant but nonlinear trend in the data over time (eg, a leveling off or significant change in direction). Trends that include significant linear and quadratic components demonstrate nonlinear variation in addition to an overall increase or decrease over time.

RESULTS

During 1991-2005, the prevalence of sexual experience decreased 13% from 54.1% to 46.8% among high school students. Logistic regression analyses indicated a significant linear decrease overall and among female, male, 9th-grade, 10th-grade, 11th-grade, 12th-grade, black, and white students (Table 1). A significant quadratic trend also was detected among black students and 11th-grade students. …