HIV Instruction, HIV Knowledge, and Drug Injection among High School Students in the United States
Deborah Holtznan; PhD, John E. Anderson, PhD, Laura Kann, PhD, Susan L. Arday, MHS, Benedict I. Tnsman, MD, MPH, and Lloyd J. Kolbe, PhD
Inrodudion This article describes the prevalence of self-reported illicit drug injection among high school students in the United States and examines the relationships among school-based instruction about human immunodeficiency virus (HIV), HIV knowledge, and drug-injection behavior. Although the incidence of acquired immunodeficiency syndrome (AIDS) in US adolescents is not as high as it is in adults and children, each of these groups has experienced a rapid rate of growth in the cumulative incidence of the disease in the last decade."2 Because of the long latency period for HIV, which may average 10 years or more,3 it is also likely that many of the 20- to 29-year-olds diagnosed with AIDS, who account for 20% of all cases nationwide,4 were infected with HIV during adolescence. Indeed, many adolescents engage in behaviors that place them at risk for HIV infection. As of July 1990, 40% of the AIDS cases in the United States reported among 13- to 19-year-olds resulted from sexual transmission of HIV, 11% of cases reported histories of intravenous (IV) drug use, and another 4% reported both risk behaviors.4 In national surveys, reported rates of sexual intercourse among 17- to 19-yearold, never-married males in metropolitan areas increased from 65.7% in 1979 to 75.5% in 1988.5 In similar surveys of US females, the rates of premarital sexual intercourse among 15- to 19-year-old adolescents living in metropolitan areas increased from 43.4% in 1979 to 45.2% in 1982.6 Further, a 1979 survey of adolescent females revealed that their mean age at first intercourse was 16.2 years and that 16% of the sample reported four or more
sexual partners.7.8 In a 1989 nationwide survey, 58.5% of 9th- through 12th-grade students had had sexual intercourse, and of these, 40.4% reported four or more partners. In addition, 23.3% of the students who ever had sex reported that they never used a condom when they had sexual intercourse.9 IV drug use has also been reported in surveys of youth, but the extent and nature of illicit drug-injection behavior among adolescents has not been well studied. Surveys of IV drug use in relatively small or geographically limited populations of adolescents have shown considerable variation in rates, ranging from 0.1 to 6.3%.1-15 How prevalent, then, is IV drug use among adolescents in the United States? And equally important, what factors influence this behavior?16 Several surveys ofHV-related lowledge, attitudes, and behaviors among adolescents have been reported,5"1-15"17"18 but only one was nationwide in scope,13 Deborah Holtzman, Laura Kann, Susan L. Arday, Benedict I. Truman, and Uoyd J. Kolbe are with the Division of Adolescent and School Health, National Center for Chronic Disease Prevention and Health Promotion, and John E. Anderson is with the Division of STDIHIV Prevention, National Center for Prevention Services, all at the Centers for Disease Control, Atlanta, Ga. Requests for reprints should be sent to Deborah Holtzrnan, PhD, Division of Adolescent and School Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control, Mailstop K-33, 1600 Clifton Road, NE, Atlanta, GA 30333. This paper was submitted to the journal November 15, 1990, and accepted with revisions April 4, 1991. Editor's Note. See related Editorial by Hinman on page 1557.
December 1991, Vol. 81, No. 12
HKV
only a few assessed risk behaviors for HIV
by the questionnaire: demographic char-
infection,1'-4Z'4,'5 and fewer still have analyzed possible detemiinants of these behaviors."1 As part of a system of surveys for collecting school-based data, the Centers for Disease Control conducted the Secondary School Student Health Risk Survey (SSSHRS) in April and May of 1989. The SSSHRS was the first survey to collect data about HIV-related knowledge, beliefs, and behaviors among a nationally representative sample of US students in grades 9 through 12. Two variables that may be possible determinants of behavioral risk reduction-HIV instruction and HIV knowledge-were measured by the survey. The SSSHRS also collected data about sexual activity and illicit drug injection. This report focuses on the latter. First, we examined the prevalence of injected drug use among high school students. Second, we examined whether students who had received classroom instruction about HIV andwho had a greater level of HIV knowledge were less likely than other students to have injected dnrgs or shared needles. With this information we can better plan and evaluate our HIV educational efforts for adolescents.
acteristics, HIV instruction, HIV attitudes, HIV knowledge, and HIV-related risk behaviors. Variables used in the current analysis are descnbed in more detail below. HIV Instruction, Knowledge, and Behaior. A single question, answeredyes or no, was used to measure HIV instruction. Students were asked, "Have you been taught about AIDS/H1V infection in school?" Seventeen items measured HIV knowledge. Students were asked about such factors as modes of HIV transmission and how to reduce risk for HIV infection. Based on the number of correct responses to the 17 items, a score was computed for each respondent, with equal weight given to each question. Drug-injection behavior was assessed by four dichotomous dependentvariables. Students were asked if they had done the following: (1) ever injected illicit drugs, (2) injected illicit drugs in the lastyear, (3) ever shared needles, or (4) shared needles in the last
Medods Stuy Population The sampling frame, which consisted of all US public- and private-school students in grades 9 through 12, was divided into 1921 primary sampling units (PSUs) and stratified by region and urbanicity. Fifty PSUs were selected and, from these PSUs, 50 counties were selected. From the 50 counties, 122 schools were selected. At each stage, the sample was selected with probability proportional to the size of the 9th through 12th grade enrollment. Heavily Black and Hispanic areas were oversampled. Within participating schools, one or two classes of a reqiired subject were randomly selected.
year.
Data Analysis Two separate multivariate analyses were conducted to examine relationships among HIV knowledge, HIV instruction,
and drug-injection behavior. Using multiple linear regression, HIV knowledge was regressed on HIV instruction, while controlling for age, sex, racial or ethnic group, and the interactions between HIV instruction and sex, and between HIV instruction and racial or ethnic group. Using stepwise multiple logistic regression, each of the four drug-behavior variables was regressed on HIV instruction and HIV knowledge, controlling for the same back-
-, Knowdge, and Dnog Ijedon
ground characteristics. There are theoretical and empirical reasons for including both HIV instruction and knowledge in the models. Theoretically, for instruction to have an effect on drugbehavior itwould likely work through some other mechanism, such as knowledge or attitudes. Without knowledge, then, the model would be improperly specified, and would bias the effect of instruction on drug behavior. In addition, a comparison of the model with knowledge and without knowledge showed that the effect of HIV instruction on drug behavior did not change. A further complication arises, however, if HIV instruction and HIV knowledge are highly correlated. This was examined by the authors and the correlation between the two variables was found to be relatively low (r = .21), suggesting that multicollinearity was not a problem in the analysis. Since very few students reported having shared needles within categories of racial or ethnic group and HIV instruction, the effect of these interactions on sharing needles could not be evaluated. Additionally, because the interactions between knowledge and each demographic characteristic and between HIV instruction and age were all highly correlated (r > .82) with at least one of the main effects, these terms were excluded from all models. All main effects, regardless of the level of signifcance, were retained in the models when the interaction term was significant.19 All data were weighted to compensate for nonresponse within categories of age, grade, and sex, and the fact that not all students were sampled with the same likelihood. The SAS programmig
Data Collection Representatives from numerous federal, state, and local education agencies and experts in HIV and reproductive health behaviors were involved in developing the survey instrument. Personnel were trained to coordinate on-site data collection, and special measures were taken to protect student anonymity. A 39item questionnaire was designed to be self-administered in the classroom. Five broad groups of variables were assessed December 1991, Vol. 81, No. 12
American Journal of Public Health 1597
H ditman et aL
language was used to conduct the analyses,20 and statistical tests and confidence intervals were based on the procedures SURREGR, SESUDAAN, and RTILOGIT, which take into account the complex sample design.21-23 Results were considered significant if the Pvalue for the calculated statistic was less than or equal to .05.
Results Of the 122 schools selected, 99 (81%) participated. Selected schools and participating schools were compared by region, metropolitan or nonmetropolitan area, and racial or ethnic group (Table 1). Only small differences were observed within each category, suggesting that school-level nonresponse did not greatly bias the sample. Of selected students, 10%o did not receive parental permission to participate and an additional 7% were absent when the surveywas administered and on the scheduled make-up day(s). Usable questionnaires were received from 8098 (83%) of the eligible sample. Based on the schooland student-level response, an overall response rate of 67% was obtained. Participants were fairly evenly distributed by grade and sex (Table 2). The weighted percentages of White, Black, and Hispanic students who participated were similar to estimates of the racial and ethnic distribution of 9th- through 12thgrade students in the United States. For the US population of students in these grades, the estimates were 70.8% White, 15.5% Black, and 8.9% Hispanic.24 (Calculations for general population estimates of high school students were also based on unpublished data from US Bureau of the Census, Annual Projections of the Population by Age, Sex, Race, for the United States: 1983 to 2080, Hispanic by race data, July 1, 1988.) Slightly over half (53.7%) of those surveyed said they had received instruction in school about AIDS and HlV infection (Table 3). Significant differences in the proportion of students reporting HIV instruction were found by age and grade only. Students who were 17 or more years of age were less likely than 15- and 16year-old students to have received HIV instruction (P < .05), and 12th-grade students were less likely than 10th- or llthgrade students to have received instruction (P < .05). For all students, an average of 14.5 knowledge items were answered correctly (range = 0-17). The vast majority of students knew that AIDS/HIV infection is 1598 American Journal of Public Health
transmitted during sexual intercourse (97.7%), by sharing needles (98.9%), and perinatally (90.7%). Most also knew that HIV infection is not transmitted by casual contact. Students were less informed about transmission of the virus in other ways; only 64.0% knew the virus could not be transmitted by donating blood, and only 45.1% knew the virus could not be transmitted by insect bites. When asked about drug-injection behavior, 2.7% of students reported having ever injected illicit drugs, and 0.8% reported having ever shared needles (Table 4). The rate of ever injecting drugs was higher for males than for females (3.7% vs 1.8%, P < .05). Differences in drug-injection behavior by racial or ethnic group were not statistically significant. The reported rates of ever injecting drugs showed a clear decline from grades 9 to 12, and significant differences were observed between 9th- and 12th-grade students (P < .05). No significant differences, however, were found by age group. Finally, students who reported having been taught about HIV were less likely than those who reported no instruction to have ever injected drugs (P < .05). Results of logistic regression analysis showed that HIV knowledge, being male, and the interactions between HIV instruction and being male and between H1V instruction and being Black all had significant effects on ever injecting drugs (Table 5). The greater the level of knowledge, the less likely students were to report ever
injecting drugs. Males were more likely than females to have injected drugs, although males who had received HIV instruction were less likely to have injected
December 1991, Vol. 81, No. 12
HIV lntuction, Knowldge, and Dnug Iecto
drugs when compared with males who had not received HIV instruction and with females. Further, Black students who had received HIV instruction were less likely to have ever injected drugs when compared with Blacks who had not received instruction and with students of other racial or ethnic groups. No significant direct effect of HIV instruction on ever injecting drugs was found. Drug injection in the last year was significantly associated with level of HIV knowledge and sex (Table 6). The greater
December 1991, Vol. 81, No. 12
the level of knowledge, the less likely students were to have injected drugs in the last year, but, as with lifetime drug-injection behavior, males were significantly more likely than females to report the behavior in the lastyear. Again, therewas no direct effect of HIV instruction on last year drug-injection behavior. Similar results were found for those who reported ever sharing needles or sharing needles in the last year (Tables 7 and 8). The greater the level of knowledge, the less likely students were to have ever
shared needles or to have shared needles in the last year. While the difference between males and females in ever sharing needles was not quite statistically significant, males were significantly more likely than females to have shared needles in the last year. In additional analyses, not shown here, we found that students who reported injecting drugs and sharing needles were more likely to report multiple sexual partners (defined as two or more) and to report never using condoms when having sex.
American Journal of Public Health 1599
Hdltzman et al.
dependent of demographic characteristics, it was significantly associated with HIV knowledge (Table 9). When we controlled for demographic characteristics, students who had received HIV instruction were more likely than students who had not received instruction to have a greater level of HIV knowledge. Specifically, students who received HIV instruction in school answered, on average, almost one additional item correctly. Age, being male, and racial or ethnic group were also significantly related to HIV knowledge. Studentswho were older and those who were White were more likely to have a higher level of knowledge about HIV, compared to younger students and those in the other racial or ethnic groups. Males, on the other hand, had a significantly lower level of knowledge about HIV than females did. Also, in additional regression analyses, we found that within the subgroup of students who reported multiple sexual partners and within the subgroup of those who reported never using condoms, HIV instruction and knowledge had the same effect on ever injecting drugs and ever sharing needles that was demonstrated in our analysis of all students. The greater the level of knowledge, the less likely students were to report ever injecting drugs and ever sharing needles. Furthermore, within the subgroup of students with multiple sexual partners, Black students who had been taught about HIV were less likely than Black students who had not received instruction and students of other racial or ethnic groups to report ever injecting drugs. Finally, within the subgroup of students who reported never using condoms, males who had received HIV instruction were less likely than noninstructed males and females to have ever injected drugs. Thus, even for students who engage in risky sexual behaviors, HIV knowledge and, for some students, HIV instruction continue to exert a positive influence on HIV-related drug behavior. Finally, we examined the relationship between each HIV knowledge item and each of the drug behavior variables to see which items might be most predictive of the behaviors. Most highly negatively correlated with ever injecting drugs and ever sharing needles were correct responses to four items that asked about transmission of HIV through sharing needles and sexual intercourse. Although HIV instruction did not have a significant direct effect on druginjection and needle-sharing behavior in1600 American Journal of Public Health
Discussion Although the results of our survey showed that illicit drug-injection behavior was not common among the nation's high school students, it was reported by some students-more frequently by males and by those who had not received HIV instruction in school. The percentage of high school students who have injected illicit drugs is a cause for concern, however. If 2.7% of the nation's 9th- through 12thgrade students have injected drugs and 0.8 percent have shared needles, then approximately 345 100 and 102 200,24 respectively, may have already engaged in behaviors that can quite efficiently transmit the virus that causes AIDS. Moreover, students who inject drugs may be less likely to remain in school than students who do not. The observed decrease in drug-injection behavior by grade, and to some extent by age, could be attributed to the fact that dropout rates increase with grade-a phenomenon that, in tum, may be exacerbated by drug use. Indeed, one study showed a higher rate of drug use among dropouts than among inschool youth.25 When HIV instruction and demographic characteristics were taken into account, HIV knowledge was found to be associated with lower levels of drug-injection and needle-sharing behavior. And although males were more likely than females to report these behaviors, the results suggested that males who had received HIV instruction were less likely than uninstructed males to have ever injected drugs. Similarly, Blacks who had received HIV instruction were signifi-
cantly less likely to report ever injecting drugs than were Black students who had not received instruction and students of other racial and ethnic groups. These results are particularly promising, because Blacks and males in the United States are disproportionately affected by AIDS.2-28 Further, HIV instruction was significantly associated with an increased level of HIV knowledge among students, which in turn, was associated with lower levels of druginjection and needle-sharing behavior. Although these results have important implications for HIV education, some limitations of the data are important to consider. First, because the SSSHRS was a cross-sectional survey, causal relationships among the variables cannot be established. In addition, other variables that may have an effect on drug-injection behavior could not be accounted for in the analysis-for example, educational performance, socioeconomic status, peer norms, or drug availability. Also, because the data were self-reported, under- or overreporting may have occurred, especially given the sensitive nature of the behavior questions. Finally, since the data are school-based, the results can be generalized only to adolescents who attend school. The data, however, were from a large, population-based sample; a number ofvariables were available for control; and more than one type of behavioral outcome was assessed. The prevalence of druginjection behavior among secondary school students in the United States found by the SSSHRS was similar to other estimates of drug injection in this population,12,15 and the analysis demonstrated that HIV knowledge does affect this behavior. In a study of adults, HIV knowledge was also shown to be a predictor of behavioral risk reduction.29 Further, the effect of knowledge was significant for each indicator of drug-injection behavior in the current analysis. A similar effect of HIV knowledge was found when it was examined in relation to sexual behavior and condom use in the SSSHRS; that is, the greater the level of knowledge, the fewer the number of sexual partners and the higher the level of condom use.9 Our results were also strengthened by an association between increased levels of HIV knowledge and lower levels of reported drug-injection and needle-sharing behavior within two subgroups of students at increased risk of HIV-those who reported two or more lifetime sexual partners and those who reported never using condoms when having sex. December 1991, Vol. 81, No. 12
HIV Instuction, Knowledge, and Drug Injection
.............S ...
.... ... ... ...
a...........
..
o...
..
------ --
--
-- --
--
Acknowledgments .
-- --
.......S.
b..
n...... ....................E
........12813...0.38. ge'.......
0110..
hILV...........
..7
~~~~,p
Deborah Holtznan; PhD, John E. Anderson, PhD, Laura Kann, PhD, Susan L. Arday, MHS, Benedict I. Tnsman, MD, MPH, and Lloyd J. Kolbe, PhD
Inrodudion This article describes the prevalence of self-reported illicit drug injection among high school students in the United States and examines the relationships among school-based instruction about human immunodeficiency virus (HIV), HIV knowledge, and drug-injection behavior. Although the incidence of acquired immunodeficiency syndrome (AIDS) in US adolescents is not as high as it is in adults and children, each of these groups has experienced a rapid rate of growth in the cumulative incidence of the disease in the last decade."2 Because of the long latency period for HIV, which may average 10 years or more,3 it is also likely that many of the 20- to 29-year-olds diagnosed with AIDS, who account for 20% of all cases nationwide,4 were infected with HIV during adolescence. Indeed, many adolescents engage in behaviors that place them at risk for HIV infection. As of July 1990, 40% of the AIDS cases in the United States reported among 13- to 19-year-olds resulted from sexual transmission of HIV, 11% of cases reported histories of intravenous (IV) drug use, and another 4% reported both risk behaviors.4 In national surveys, reported rates of sexual intercourse among 17- to 19-yearold, never-married males in metropolitan areas increased from 65.7% in 1979 to 75.5% in 1988.5 In similar surveys of US females, the rates of premarital sexual intercourse among 15- to 19-year-old adolescents living in metropolitan areas increased from 43.4% in 1979 to 45.2% in 1982.6 Further, a 1979 survey of adolescent females revealed that their mean age at first intercourse was 16.2 years and that 16% of the sample reported four or more
sexual partners.7.8 In a 1989 nationwide survey, 58.5% of 9th- through 12th-grade students had had sexual intercourse, and of these, 40.4% reported four or more partners. In addition, 23.3% of the students who ever had sex reported that they never used a condom when they had sexual intercourse.9 IV drug use has also been reported in surveys of youth, but the extent and nature of illicit drug-injection behavior among adolescents has not been well studied. Surveys of IV drug use in relatively small or geographically limited populations of adolescents have shown considerable variation in rates, ranging from 0.1 to 6.3%.1-15 How prevalent, then, is IV drug use among adolescents in the United States? And equally important, what factors influence this behavior?16 Several surveys ofHV-related lowledge, attitudes, and behaviors among adolescents have been reported,5"1-15"17"18 but only one was nationwide in scope,13 Deborah Holtzman, Laura Kann, Susan L. Arday, Benedict I. Truman, and Uoyd J. Kolbe are with the Division of Adolescent and School Health, National Center for Chronic Disease Prevention and Health Promotion, and John E. Anderson is with the Division of STDIHIV Prevention, National Center for Prevention Services, all at the Centers for Disease Control, Atlanta, Ga. Requests for reprints should be sent to Deborah Holtzrnan, PhD, Division of Adolescent and School Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control, Mailstop K-33, 1600 Clifton Road, NE, Atlanta, GA 30333. This paper was submitted to the journal November 15, 1990, and accepted with revisions April 4, 1991. Editor's Note. See related Editorial by Hinman on page 1557.
December 1991, Vol. 81, No. 12
HKV
only a few assessed risk behaviors for HIV
by the questionnaire: demographic char-
infection,1'-4Z'4,'5 and fewer still have analyzed possible detemiinants of these behaviors."1 As part of a system of surveys for collecting school-based data, the Centers for Disease Control conducted the Secondary School Student Health Risk Survey (SSSHRS) in April and May of 1989. The SSSHRS was the first survey to collect data about HIV-related knowledge, beliefs, and behaviors among a nationally representative sample of US students in grades 9 through 12. Two variables that may be possible determinants of behavioral risk reduction-HIV instruction and HIV knowledge-were measured by the survey. The SSSHRS also collected data about sexual activity and illicit drug injection. This report focuses on the latter. First, we examined the prevalence of injected drug use among high school students. Second, we examined whether students who had received classroom instruction about HIV andwho had a greater level of HIV knowledge were less likely than other students to have injected dnrgs or shared needles. With this information we can better plan and evaluate our HIV educational efforts for adolescents.
acteristics, HIV instruction, HIV attitudes, HIV knowledge, and HIV-related risk behaviors. Variables used in the current analysis are descnbed in more detail below. HIV Instruction, Knowledge, and Behaior. A single question, answeredyes or no, was used to measure HIV instruction. Students were asked, "Have you been taught about AIDS/H1V infection in school?" Seventeen items measured HIV knowledge. Students were asked about such factors as modes of HIV transmission and how to reduce risk for HIV infection. Based on the number of correct responses to the 17 items, a score was computed for each respondent, with equal weight given to each question. Drug-injection behavior was assessed by four dichotomous dependentvariables. Students were asked if they had done the following: (1) ever injected illicit drugs, (2) injected illicit drugs in the lastyear, (3) ever shared needles, or (4) shared needles in the last
Medods Stuy Population The sampling frame, which consisted of all US public- and private-school students in grades 9 through 12, was divided into 1921 primary sampling units (PSUs) and stratified by region and urbanicity. Fifty PSUs were selected and, from these PSUs, 50 counties were selected. From the 50 counties, 122 schools were selected. At each stage, the sample was selected with probability proportional to the size of the 9th through 12th grade enrollment. Heavily Black and Hispanic areas were oversampled. Within participating schools, one or two classes of a reqiired subject were randomly selected.
year.
Data Analysis Two separate multivariate analyses were conducted to examine relationships among HIV knowledge, HIV instruction,
and drug-injection behavior. Using multiple linear regression, HIV knowledge was regressed on HIV instruction, while controlling for age, sex, racial or ethnic group, and the interactions between HIV instruction and sex, and between HIV instruction and racial or ethnic group. Using stepwise multiple logistic regression, each of the four drug-behavior variables was regressed on HIV instruction and HIV knowledge, controlling for the same back-
-, Knowdge, and Dnog Ijedon
ground characteristics. There are theoretical and empirical reasons for including both HIV instruction and knowledge in the models. Theoretically, for instruction to have an effect on drugbehavior itwould likely work through some other mechanism, such as knowledge or attitudes. Without knowledge, then, the model would be improperly specified, and would bias the effect of instruction on drug behavior. In addition, a comparison of the model with knowledge and without knowledge showed that the effect of HIV instruction on drug behavior did not change. A further complication arises, however, if HIV instruction and HIV knowledge are highly correlated. This was examined by the authors and the correlation between the two variables was found to be relatively low (r = .21), suggesting that multicollinearity was not a problem in the analysis. Since very few students reported having shared needles within categories of racial or ethnic group and HIV instruction, the effect of these interactions on sharing needles could not be evaluated. Additionally, because the interactions between knowledge and each demographic characteristic and between HIV instruction and age were all highly correlated (r > .82) with at least one of the main effects, these terms were excluded from all models. All main effects, regardless of the level of signifcance, were retained in the models when the interaction term was significant.19 All data were weighted to compensate for nonresponse within categories of age, grade, and sex, and the fact that not all students were sampled with the same likelihood. The SAS programmig
Data Collection Representatives from numerous federal, state, and local education agencies and experts in HIV and reproductive health behaviors were involved in developing the survey instrument. Personnel were trained to coordinate on-site data collection, and special measures were taken to protect student anonymity. A 39item questionnaire was designed to be self-administered in the classroom. Five broad groups of variables were assessed December 1991, Vol. 81, No. 12
American Journal of Public Health 1597
H ditman et aL
language was used to conduct the analyses,20 and statistical tests and confidence intervals were based on the procedures SURREGR, SESUDAAN, and RTILOGIT, which take into account the complex sample design.21-23 Results were considered significant if the Pvalue for the calculated statistic was less than or equal to .05.
Results Of the 122 schools selected, 99 (81%) participated. Selected schools and participating schools were compared by region, metropolitan or nonmetropolitan area, and racial or ethnic group (Table 1). Only small differences were observed within each category, suggesting that school-level nonresponse did not greatly bias the sample. Of selected students, 10%o did not receive parental permission to participate and an additional 7% were absent when the surveywas administered and on the scheduled make-up day(s). Usable questionnaires were received from 8098 (83%) of the eligible sample. Based on the schooland student-level response, an overall response rate of 67% was obtained. Participants were fairly evenly distributed by grade and sex (Table 2). The weighted percentages of White, Black, and Hispanic students who participated were similar to estimates of the racial and ethnic distribution of 9th- through 12thgrade students in the United States. For the US population of students in these grades, the estimates were 70.8% White, 15.5% Black, and 8.9% Hispanic.24 (Calculations for general population estimates of high school students were also based on unpublished data from US Bureau of the Census, Annual Projections of the Population by Age, Sex, Race, for the United States: 1983 to 2080, Hispanic by race data, July 1, 1988.) Slightly over half (53.7%) of those surveyed said they had received instruction in school about AIDS and HlV infection (Table 3). Significant differences in the proportion of students reporting HIV instruction were found by age and grade only. Students who were 17 or more years of age were less likely than 15- and 16year-old students to have received HIV instruction (P < .05), and 12th-grade students were less likely than 10th- or llthgrade students to have received instruction (P < .05). For all students, an average of 14.5 knowledge items were answered correctly (range = 0-17). The vast majority of students knew that AIDS/HIV infection is 1598 American Journal of Public Health
transmitted during sexual intercourse (97.7%), by sharing needles (98.9%), and perinatally (90.7%). Most also knew that HIV infection is not transmitted by casual contact. Students were less informed about transmission of the virus in other ways; only 64.0% knew the virus could not be transmitted by donating blood, and only 45.1% knew the virus could not be transmitted by insect bites. When asked about drug-injection behavior, 2.7% of students reported having ever injected illicit drugs, and 0.8% reported having ever shared needles (Table 4). The rate of ever injecting drugs was higher for males than for females (3.7% vs 1.8%, P < .05). Differences in drug-injection behavior by racial or ethnic group were not statistically significant. The reported rates of ever injecting drugs showed a clear decline from grades 9 to 12, and significant differences were observed between 9th- and 12th-grade students (P < .05). No significant differences, however, were found by age group. Finally, students who reported having been taught about HIV were less likely than those who reported no instruction to have ever injected drugs (P < .05). Results of logistic regression analysis showed that HIV knowledge, being male, and the interactions between HIV instruction and being male and between H1V instruction and being Black all had significant effects on ever injecting drugs (Table 5). The greater the level of knowledge, the less likely students were to report ever
injecting drugs. Males were more likely than females to have injected drugs, although males who had received HIV instruction were less likely to have injected
December 1991, Vol. 81, No. 12
HIV lntuction, Knowldge, and Dnug Iecto
drugs when compared with males who had not received HIV instruction and with females. Further, Black students who had received HIV instruction were less likely to have ever injected drugs when compared with Blacks who had not received instruction and with students of other racial or ethnic groups. No significant direct effect of HIV instruction on ever injecting drugs was found. Drug injection in the last year was significantly associated with level of HIV knowledge and sex (Table 6). The greater
December 1991, Vol. 81, No. 12
the level of knowledge, the less likely students were to have injected drugs in the last year, but, as with lifetime drug-injection behavior, males were significantly more likely than females to report the behavior in the lastyear. Again, therewas no direct effect of HIV instruction on last year drug-injection behavior. Similar results were found for those who reported ever sharing needles or sharing needles in the last year (Tables 7 and 8). The greater the level of knowledge, the less likely students were to have ever
shared needles or to have shared needles in the last year. While the difference between males and females in ever sharing needles was not quite statistically significant, males were significantly more likely than females to have shared needles in the last year. In additional analyses, not shown here, we found that students who reported injecting drugs and sharing needles were more likely to report multiple sexual partners (defined as two or more) and to report never using condoms when having sex.
American Journal of Public Health 1599
Hdltzman et al.
dependent of demographic characteristics, it was significantly associated with HIV knowledge (Table 9). When we controlled for demographic characteristics, students who had received HIV instruction were more likely than students who had not received instruction to have a greater level of HIV knowledge. Specifically, students who received HIV instruction in school answered, on average, almost one additional item correctly. Age, being male, and racial or ethnic group were also significantly related to HIV knowledge. Studentswho were older and those who were White were more likely to have a higher level of knowledge about HIV, compared to younger students and those in the other racial or ethnic groups. Males, on the other hand, had a significantly lower level of knowledge about HIV than females did. Also, in additional regression analyses, we found that within the subgroup of students who reported multiple sexual partners and within the subgroup of those who reported never using condoms, HIV instruction and knowledge had the same effect on ever injecting drugs and ever sharing needles that was demonstrated in our analysis of all students. The greater the level of knowledge, the less likely students were to report ever injecting drugs and ever sharing needles. Furthermore, within the subgroup of students with multiple sexual partners, Black students who had been taught about HIV were less likely than Black students who had not received instruction and students of other racial or ethnic groups to report ever injecting drugs. Finally, within the subgroup of students who reported never using condoms, males who had received HIV instruction were less likely than noninstructed males and females to have ever injected drugs. Thus, even for students who engage in risky sexual behaviors, HIV knowledge and, for some students, HIV instruction continue to exert a positive influence on HIV-related drug behavior. Finally, we examined the relationship between each HIV knowledge item and each of the drug behavior variables to see which items might be most predictive of the behaviors. Most highly negatively correlated with ever injecting drugs and ever sharing needles were correct responses to four items that asked about transmission of HIV through sharing needles and sexual intercourse. Although HIV instruction did not have a significant direct effect on druginjection and needle-sharing behavior in1600 American Journal of Public Health
Discussion Although the results of our survey showed that illicit drug-injection behavior was not common among the nation's high school students, it was reported by some students-more frequently by males and by those who had not received HIV instruction in school. The percentage of high school students who have injected illicit drugs is a cause for concern, however. If 2.7% of the nation's 9th- through 12thgrade students have injected drugs and 0.8 percent have shared needles, then approximately 345 100 and 102 200,24 respectively, may have already engaged in behaviors that can quite efficiently transmit the virus that causes AIDS. Moreover, students who inject drugs may be less likely to remain in school than students who do not. The observed decrease in drug-injection behavior by grade, and to some extent by age, could be attributed to the fact that dropout rates increase with grade-a phenomenon that, in tum, may be exacerbated by drug use. Indeed, one study showed a higher rate of drug use among dropouts than among inschool youth.25 When HIV instruction and demographic characteristics were taken into account, HIV knowledge was found to be associated with lower levels of drug-injection and needle-sharing behavior. And although males were more likely than females to report these behaviors, the results suggested that males who had received HIV instruction were less likely than uninstructed males to have ever injected drugs. Similarly, Blacks who had received HIV instruction were signifi-
cantly less likely to report ever injecting drugs than were Black students who had not received instruction and students of other racial and ethnic groups. These results are particularly promising, because Blacks and males in the United States are disproportionately affected by AIDS.2-28 Further, HIV instruction was significantly associated with an increased level of HIV knowledge among students, which in turn, was associated with lower levels of druginjection and needle-sharing behavior. Although these results have important implications for HIV education, some limitations of the data are important to consider. First, because the SSSHRS was a cross-sectional survey, causal relationships among the variables cannot be established. In addition, other variables that may have an effect on drug-injection behavior could not be accounted for in the analysis-for example, educational performance, socioeconomic status, peer norms, or drug availability. Also, because the data were self-reported, under- or overreporting may have occurred, especially given the sensitive nature of the behavior questions. Finally, since the data are school-based, the results can be generalized only to adolescents who attend school. The data, however, were from a large, population-based sample; a number ofvariables were available for control; and more than one type of behavioral outcome was assessed. The prevalence of druginjection behavior among secondary school students in the United States found by the SSSHRS was similar to other estimates of drug injection in this population,12,15 and the analysis demonstrated that HIV knowledge does affect this behavior. In a study of adults, HIV knowledge was also shown to be a predictor of behavioral risk reduction.29 Further, the effect of knowledge was significant for each indicator of drug-injection behavior in the current analysis. A similar effect of HIV knowledge was found when it was examined in relation to sexual behavior and condom use in the SSSHRS; that is, the greater the level of knowledge, the fewer the number of sexual partners and the higher the level of condom use.9 Our results were also strengthened by an association between increased levels of HIV knowledge and lower levels of reported drug-injection and needle-sharing behavior within two subgroups of students at increased risk of HIV-those who reported two or more lifetime sexual partners and those who reported never using condoms when having sex. December 1991, Vol. 81, No. 12
HIV Instuction, Knowledge, and Drug Injection
.............S ...
.... ... ... ...
a...........
..
o...
..
------ --
--
-- --
--
Acknowledgments .
-- --
.......S.
b..
n...... ....................E
........12813...0.38. ge'.......
0110..
hILV...........
..7
~~~~,p
