ALCOHOL A N D MARIJUANA USE A M O N G ADOLESCENTS: LONG-TERM OUTCOMES OF THE CLASS OF 1989 STUDY 1
Knut-lnge Klepp, Ph.D. University o f Bergen, N o r w a y
Steven H. Kelder, Ph.D. University o f Texas Health Science Center at Houston Cheryl L. Perry, Ph.D. University o f Minnesota
ABSTRACT
1990 according to curriculum content. He concluded that C o m prehensive and Social Influence programs were most successful in preventing the onset o f substance use compared to other intervention techniques such as Information/Values Clarification, Affective Education, and Alternatives programs. Comprehensive and Social Influence programs are characterized b y a focus on teaching students about peer and other social pressures and developing skills to resist these pressures. The programs often include information about substance use, resistance skills training, pledges not to use substances and norm setting, a n d nearly all o f them feature peer leaders who assist with program delivery. The Comprehensive programs included a broader spectrum o f prevention strategies, including decision making, than did the Social Influence programs. A number o f recent Comprehensive and Social Influence programs have reported positive short-term results with respect to reduced onset o f alcohol and marijuana use (6-I0). While delaying the onset o f drug use among adolescents is a major goal o f such programs, reducing the long-term incidence o f drug-related injuries and chronic diseases is the ultimate goal. However, the long-term impact o f these educational programs on alcohol and marijuana use still remains to be seen. In this article we report on both the short-term and longterm results o f an educational program, "Shifting Gears," designed to reduce alcohol use, drinking and driving behavior, and marijuana use in a cohort o f high school students. "Shifting Gears" was implemented as part o f the Class o f 1989 Study, a substudy o f the Minnesota Heart Health Program (MHHP). M H H P is a population-wide research a n d demonstration project designed to reduce cardiovascular disease (CVD) in three educated communities (1980-1993). The education communities received five years o f M H H P community-wide risk reduction interventions including mass media, c o m m u n i t y organization, risk factor screening, adult education, and schoolbased youth interventions, and were compared to matched reference communities (11,12). M H H P focused on changes in cating habits, physical activity levels, cigarette smoking, and adberence to hypertension medication. The larger project did not seek changes in adolescent and adult alcohol or marijuana use. In the Class o f 1989 Study, students in the M H H P intervention c o m m u n i t y o f Fargo and West Fargo, N o r t h Dakota, and o f Moorhead, Minnesota, received school-based interventions designed to favorably influence their smoking, physical activity levels, and eating behaviors each year from 1983 to 1987. During the school year o f 1985-1986 when students were in ninth grade, the program, called "Shifting Gears," which
The Minnesota Heart Health Program (MHHP) is a population-wide research and demonstration project designed to reduce cardiovascular disease in three educated communities (19801993) compared to three matched reference communities. The Class of 1989 Study, a substudy of the MHHP, collected selfreported data in one educated and one matched reference community. All sixth graders enrolled in both communities were invited to participate in a baseline survey in 1983, and that grade cohort was surveyed annually throughout junior high and high school until 1989. Students received interventions designed to favorably influence their smoldng, physical activity levels, and eating behavior each year.from 1983 to 1987. As part of this five-year intervention, a program addressing smoldng, alcohol use, drinking and driving behavior, and marijuana use was implemented during the school year o f 1985-1986, when students were in ninth grade. Using the school as the unit o f analysis, we found that students in the intervention community in 1986 reported fewer occasions on which they had been drinldng alcohol in the past 30 days than did students in the reference community. Furthermore, students in the intervention community reported less problem drinldng in the previous two weeks and less driving after drinldng than did students in the reference community. These positive intervention effects were not maintained through twelfth grade. (Ann Behav Med
1995, 17(1):19-24)
INTRODUCTION Literature reviewing the impact o f educational programs designed to delay the onset o f alcohol and marijuana use among adolescents has often concluded that there is little or contradicting evidence regarding the effectiveness o f p r i m a r y prevention programs (1--4). In a recent review, Hansen (5) classified substance use prevention programs published between 1980 and
1 Preparation of this manuscript was supported in part by grant R01 HL 25523 from the National Heart, Lung and Blood Institute.
Reprint Address: C. L. Perry, Ph.D., Division of Epidemiology, School of Public Health, University of Minnesota, 1300 South Second Street, Minneapolis, MN 55454. 9 1995 by The Society of Behavioral Medicine. 19
20
ANNALS OF BEHAVIORAL MEDICINE
Klepp et al.
TABLE 1 The Class of 1989: Study Design Intervention Community (Fargo-Moorhead)
Reference Community (Sioux Falls)
Sixth grade 1982-1983
Baseline Survey I The Lunch Bag Program
Seventh grade 1983-1984
The Minnesota Smoking Prevention Program Survey II Health Olympics greeting card I
Survey II
Health Olympics greeting card II Survey III FM 250 physical activities challenge
Survey III
"Shifting Gears" Survey IV (Alcohol, marijuana use, drinking and driving questions added)
Survey IV
Eighth grade 1984-1985
Ninth grade 1985-1986
Baseline Survey I
Tenth grade 1986-1987
Slice of Life Survey V
Survey V
Eleventh grade 1987-1988
Survey VI
Survey VI
Twelt~h grade 1988-1989
Survey VII
Survey VII
[Reproduced with permission from Oxford University Press (Perry CL, Klepp K-I, Sillers C: Community-wideyouth strategies for cardiovascular health: The Minnesota Heart Health Program Youth Program. Health Education Research. 1989, 4:87-101).] addressed smoking, alcohol and marijuana use, and drinking and driving behavior, was implemented. This was done since smoking covaries with these behaviors, and it, therefore, seemed appropriate to address all of them in a school-based health program. Sioux Falls, South Dakota, served as the reference community. As has been reported elsewhere, students in the Fargo-Moorhead community reported significantly less smoking (13), more physical activity (14), and a more heart healthy diet (15) following the intervention than did students from Sioux Falls. These differences were maintained through the twelfth grade, and it was concluded that behavioral curricula in school, coupled with the supportive MHHP community-wide strategies, can produce lasting improvements in adolescent health-related behaviors. The maintenance of effects was particularly noteworthy compared with studies of school curricula alone. The alcohol and marijuana use school-based prevention program was not supported by the MHHP community-wide intervention strategies. Because of this, a unique opportunity was provided. In the present article we investigate whether students in Fargo-Moorhead reported less alcohol use, less drinking and driving, and less marijuana use than students from Sioux Falls following "Shifting Gears." In addition to assessing whether these behaviors changed after "Shifting Gears," we were able to examine the maintenance of effects to see if the results were similar to the other MHHP-targeted behaviors, where long-term maintenance was noted, or similar to other school curricula, where only short-term effects were seen. If the latter was observed, then further support for school curricula imbedded in community-wide efforts would be suggested, even though this study was not designed to directly address that question. METHODS Subjects Fargo--Moorhead and Sioux Falls, two of six MHHP communities, had been matched based on population size (about 100,000 each), socioeconomic makeup (primarily Caucasian and middle class), and distance from Minneapolis-St. Paul, Min-
nesota (250 miles). All sixth graders enrolled in Fargo-Moorhead and Sioux Falls were invited to participate in a baseline survey in April/May of 1983. This grade cohort was subsequently surveyed annually throughout high school, until graduating in 1989. From 1983 to 1986, 13 grade schools participated in the survey, and from 1987 to 1989 these same students went to 7 high schools (number of students per school ranged from 99 to 464). Participating students at baseline numbered 1,342 in the intervention community and 1,034 in the reference community. Response rates for the six follow-up periods were: 88%, 81%, 70%, 66%0, 59%, and 45%, respectively. Class of 1989 Education Class of 1989 students in Fargo--Moorhead participated in MHHP-sponsored health programs in school from sixth through tenth grade. An overview of the Class of 1989 design and educational programs is provided in Table 1. Details of the Class of 1989 school interventions and MHHP community interventions are described elsewhere (12-17). "Shifting Gears" was the only Class of 1989 or MHHP component addressing alcohol and marijuana use. Students in the reference city, Sioux Falls, did not receive any of the MHHP-sponsored community or school-based programs. Throughout the study period, these students received their school district's regular health curriculum. This curriculum did not contain any Comprehensive or Social Influence drug prevention programs. "Shifting Gears" "Shifting Gears" was a program designed to delay or prevent the onset of tobacco, alcohol, and marijuana use, and the content of the program followed a Social Influence model of intervention derived mainly from Social Learning Theory (18,19). The peer-led curriculum assumed that substance use is normative in American culture and serves a purpose for adolescents. As a result, the main emphasis of"Shifting Gears" was on why students begin to use these substances and to increase
Alcohol and Marijuana U s e Prevention their awareness that alternatives exist. Peer leaders assisted the teachers with group discussions and role play activities. The activities within "Shifting Gears" focused on building social skills enabling students to resist pressures to use drugs or engage in hazardous behaviors such as drinking and driving. The curriculum taught students how to critique and create mass media messages, thereby learning how the industry attempts to shape their behavior through advertising. Students produced storyboards for a video production which reflected their knowledge about the consequences of tobacco and alcohol use, what influenced them to use these substances, and pertinent skills and refusal techniques. A videotape was produced using the best storyboards from participating schools. Students from several schools acted in the videotape, which was then filmed and edited professionally and shown to all participating ninth grade classes. "Shifting Gears" was concerned with the functional meaning of adolescent drug use, and activities were designed to provide knowledge of health-enhancing alternative activities that serve similar functions for adolescents. The program focused on providing credible positive role models and setting a norm of non-drug use. Finally, "Shifting Gears" encouraged the practice of refusal and alternative skills via role playing and provided incentives and positive reinforcement for those alternative behaviors. A n outline of the intervention activities is presented in Table 2.
Outcome Evaluation Outcome evaluation was conducted through an annual survey completed by the students in their health, social science, or English classes. All students in the relevant grade level in school on a particular day were tested. Each year, starting in 1983, students were asked if they had ever had a drink of alcohol outside of church. Other measures of students' alcohol consumption, drinking and driving behaviors, and marijuana use were assessed annually beginning in the spring of 1986 (i.e. after the implementation of"Shifting Gears"). These measures were taken from the Monitoring the Future Study (20) and a Minnesota survey on drinking and driving behavior (21). They have all been found to have a high degree of reliability and validity when employed in studies of high school populations, and include: Alcohol Consumption: " O n how m a n y occasions have you had alcoholic beverages to drink during the last 30 days" (1 = 0 occasions; 7 = 40 occasions or more); "How many times have you had five or more drinks in a row (problem drinking) over the last two weeks" (recoded so that 0 ffi none; 100 ffi once or more often); Drinking andDriving Behavior: "During the past three months, how often have you had two or more drinks on a single occasion prior to driving a motor vehicle" (recoded so that 0 ffi none; 100 ffi once or more often); "During the past three months, how often have you had five or more drinks on a single occasion prior to driving a motor vehicle" (recoded so that 0 = none; 100 = once or more often); and Marijuana Use: "Have you ever tried marijuana" (0 = never; 1 ffi once; 2 = more than once); "During the last three months, how often have you used marijuana" (1 = never; 8 ffi every day). Other relevant measures were: age at the time of the survey, gender, and parental occupation categories.
Analysis Methods In this study, we employed a nested cohort design where whole cities were assigned to conditions. As subjects from a single community tend to be more like one another than they
VOLUME
17, N U M B E R
1, 1995
21
TABLE 2
"Shifting Gears": Summary of Intervention Activities Session 1: Teacher introduces the program. Students view a video on alcohol abuse and evaluate its effectiveness (peer-led small group discussion). Homework assignment: Read a "Video Guide" to prepare them to begin their own video production. Session 2: Discussion of negative consequences associated with people their age using alcohol (teacher-led) and reasons why people start drinking (peer-led). Complete a video pre-production worksheet determiningtarget audience and objectives for the video (peer-led). Homework assignment: Outline a realistic situation involvingalcohol use which someone their age could encounter. Session 3: Discuss situations involving alcohol use and identify positive, alternative ways of dealing with them. Select one situation for the video story board (peer-led). Discuss effective techniques to deal with difficult situations includingalcohol (peer-led). Complete and discuss a survey on drinking and driving related issues (teacher-led). Homework assignment: Bring to class two advertisements in which alcohol is being sold. Session 4: Presentation on different types of pressure used to influence people to use drugs or drink and drive (teacher-led). Analyze the role of driving in students' life (teacher-led). Identify possible alternatives or coping strategies that can be used in situations where someone feels pressured to use alcohol or drink and drive. Develop video story boards identifying types of pressures being exercised (peer-led). Homework assignment: Read the "Video Guide" about how their video will be produced. Session 5: Analyze and identify advertising pressure to use alcohol (teacher-led). Final development of each small group's video presentation. Session 6: Class presentations (role play) of video story boards. Class vote to select the presentation students feel would be the most effective in preventing alcohol use or drinking and driving in people their age.
are like subjects in the other community, the within-community correlation in the data, indexed by the community-level intraclass correlation coefficient (ICC), adds an additional component of the variability to the intervention group means above and beyond that attributable to either the individual subjects or the interventions themselves (22). Unless this component is accounted for in the analysis, the evaluation of the intervention effects will be positively biased in proportion to the magnitude of the ICC and the n u m b e r of respondents in each c o m m u n i t y (23). In the present study, students were observed in classrooms, which were nested within schools, which were nested within the towns assigned to the two treatment conditions. ICC, which reflects the within-unit correlation in the data at each level of nesting, also captures the within-unit correlation at all levels of nesting lower in the hierarchy. Thus, while we could not use the c o m m u n i t y as the unit of analysis, we could correct for most of the variance inflation expected in such a design by using the school. This was accomplished for the data gathered after 1985 using PROC GLM in SAS (24), in which a model that used the individual's response as the outcome and included school as a nested random effect was fit for each round of data; the intervention effect was tested against the school variance. Separate analyses were performed at each follow-up round. Only those
22
ANNALS OF BEHAVIORAL MEDICINE
Klepp et al. 55
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FIGURE 1: Reported number of drinking occasions (1 7 = 4 0 or more) during past 30 days.
=
RESULTS By the onset of the study in 1983, 53% of all the students reported having had at least one drink. This proportion increased rapidly over the years, and in 1989, 92% of participating students reported having been drinking at least once. There was no significant difference in lifetime prevalence of alcohol consumption between the intervention and reference communities throughout the study. We did, however, observe that in 1986, following the "Shifting Gears" intervention, ninth grade students in the intervention community reported significantly fewer drinking occasions "during the last 30 days" (Figure 1) and fewer occasions of problem drinking (five or more drinks) (Figure 2), than did students in the reference community. The point estimates remained lower in the intervention community from tenth to twelfth grade, but were not significantly different, and the differences became smaller each year (Figures 1, 2). A similar pattern was observed for drinking and driving behavior. While ninth grade students following the intervention reported significantly fewer drinking and driving occasions "during the last three months" than did students in the reference community, these differences were not maintained over time
lOth
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' 12th
.293
.310
.551
F I G U R E 2: Proportion of students reporting having had five or more drinks in a row during the last two weeks, by grade.
0;
students who participated in the baseline survey and any subsequent round of follow-up were included in the analysis, excluding those new to the community following baseline. All analyses included covariance adjustments for age and sex, and in tenth through twelfth grade, adjustments were made for parental job class. As measures of students' alcohol consumption, drinking and driving behaviors, and marijuana use were ineluded for the first time in the spring of 1986 (ninth grade), we were not able to make adjustments for the baseline or the eighth grade values of the dependent variables. Adjusted proportions or mean levels for the dependent variables, p-values, and 95% confidence intervals are presented. The confidence intervals and p-values for each follow-up period refer to comparisons between the intervention and reference conditions. Figure l also presents the degrees of freedom associated with each p-value and these remain the same for all subsequent figures.
9t'h
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(Figures 3, 4). By twelfth grade, 35% of participating students reported having driven a motor vehicle after having had t w o or more drinks on a single occasion "within the past three months." Finally, there were no significant differences between students from the two communities regarding lifetime prevalence of marijuana use or reported frequency of marijuana use "during the past three months." We observed, however, the same pattern as for alcohol use and drinking and driving, with students from the intervention communities reporting lower use rates than students from the reference communities, differences which dedined over time (Figure 5). Attrition Analysis Financial constraints precluded any attempts to contact those students who had moved out of the community, were absent, involved in work-study, or had dropped out and were not present in the class the day of the survey. The response rates were approximately equal by community with the exception of the 40 . . . . e ....
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l'lth .630
,
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9th .013
112th .666
FIGURE 3: Proportion of students reporting having had two or more drinks prior to driving during the past three months.
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lOth .142
11t" .420
~12th .713
F I G U R E 4: Proportion of students reporting having had five or more drinks prior to driving during the past three months.
last year of data collection where 55% of the intervention community students were surveyed compared to 31% in the reference community. The lower response rate in the reference group in the last year was primarily due to higher absenteeism during the survey period. For example, a senior "ditch day" occurred resulting in a large number of absentees on one of the scheduled survey days. The extent of attrition bias was approximated by identifying those missing in any given year and examining their previous year's alcohol use, drinking and driving involvement, and marijuana use. Those missing and identified the previous year were then compared to those students who were present both years. Students not present at any follow-up had a previous year value indicating that they drank alcohol, smoked marijuana, and drank before driving more often than did those students present both years. With the exception of tenth grade frequency of alcohol use and marijuana use, the differences between those missing and those present by community were not significant. This attrition bias, including the significant differences observed for tenth grade, tended to underestimate the intervention effects; that is, intervention effects may have been larger if the missing students had been recontacted. However, they still would not have been sulficient to change the lack of significance of the differences reported. Again, since we lack data for the dependent variables for eighth grade, we were not able to see what impact attrition might have had on the ninth grade values. DISCUSSION Results from this study support findings from previous studies indicating that school-based programs utilizing a Social Influence model of intervention may contribute in deterring the onset of alcohol use. Students from the Fargo-Moorhead community exposed to the "Shifting Gears" program reported, in 1986, fewer occasions on which they had been drinking alcohol in "the past 30 days," less problem drinking in "the previous two weeks" (i.e. drinking five or more drinks in a row), and less drinking and driving than did students from Sioux Falls. These differences, however, were not maintained over time and had
p-value
9th .096
l'Oth .124
'11th .270
112th .281
F I G U R E 5: Reported ever having tried marijuana (0 -- no; 1 ffi once; 2 ffi at least twice).
mostly disappeared by twelfth grade. A similar pattern, although non-significant, was seen for marijuana use. The positive intervention effects observed in the Class of 1989 Study with respect to smoking, physical activity levels, and heart healthy eating were maintained throughout high school (13-15). In contrast to students' smoking, physical activity levels, and eating behavior, the alcohol, drinking and driving, and marijuana resistance skills were not reinforced through multiple school-based interventions or by community-wide educational programs. This may explain the lack of long-term intervention impact for alcohol use and drinking and driving behavior. Thus, these results, although speculative, suggest the need for behavior-specific interventions and for consistent community-based interventions in order to achieve and maintain effects. As the Class of 1989 Study was designed to assess changes in CVD risk-related factors, frequency measures of alcohol use, drinking and driving behavior, and marijuana use were first included in the 1986 survey. Thus, we lack baseline data prior to implementing the "Shifting Gears" program, and the observed 1986 intervention effects should therefore be interpreted with caution. Each year, starting in 1983, students were, however, asked if they had ever had a drink outside church. We observed no significant difference in baseline lifetime prevalence of alcohol use. Thus, we conclude that a plausible interpretation is that the intervention effect observed in 1986 is a result of the Class of 1989 intervention. The Class of 1989 Study was designed and implemented when common research practice utilized the individual as the unit of analysis. The analyses presented in this paper, however, were conducted with the school as the unit of analysis, tending to provide a more conservative estimate of the error variance. The degrees of freedom available for 1983-1986 were df ffi 1,11 and from 1987-1989 d f = 1,5. Thus, the intervention outcomes must be considered in light of low statistical power to detect a difference, particularly in the last three years, as graphically illustrated by the wide confidence intervals in the figures. Low statistical power strengthens our conclusions for significant findings immediately following "Shifting Gears," and allows for speculative interpretation of marginally significant results such as those for marijuana (i.e. p-values of -< . 10).
24
ANNALS OF BEHAVIORAL
MEDICINE
CONCLUSION In contrast to its impact on CVD risk factors, positive intervention effects with respect to alcohol use and drinking and driving behavior were not maintained over time following the Class of 1989 Study intervention program. This finding points to the need for further investigation of the potential interaction of school-based health promotion programs with supportive community-wide strategies in order to produce lasting improvements in adolescent health-related behaviors.
REFERENCES (1) Moskowitz JM: The primary prevention of alcohol problems: A critical review of the research literature. Journal of Studies on Alcohol 1989, 50:54-88. (2) May C: Research on alcohol education for young people: A critical review of the literature. Health Education Journal 1991, 50:195199. (3) Rundall TG, Bruvold WH: A recta-analysis of school-based smoking and alcohol use prevention programs. Health Education Quarterly. 1988, 15:317-334. (4) Tobler NS: Meta-analysis of 143 adolescent drug prevention programs: Quantitative outcome results of program participants compared to a control or comparison group. Journal of Drug Issues. 1986, 16:537-567. (5) Hansen WB: School-based substance abuse prevention: A review of the state of the art in curriculum, 1980-1990. Health Education Research. 1992, 7:403-430. (6) Botvin GJ, Baker E, Dusenbury L, Tortu S, Botvin EM: Preventing adolescent drug abuse through a multimodal cognitive--behavioral approach: Results of a 3-year study. Journal of Consulting and Clinical Psychology. 1990, 58:437-446. (7) Graham JW, Johnson CA, Hansen WB, Flay BR, Gee M: Drug use prevention programs, gender, and ethnicity: Evaluation of three seventh-grade Project SMART cohorts. PreventiveMedicine. 1990, 19:305-313. (8) Hansen WB, Graham JW: Preventing alcohol, marijuana, and cigarette use among adolescents: Peer pressure resistance training versus establishing conservative norms. PreventiveMedicine. 1991, 20:414--430. (9) Penlz MA, Trebow EA, Hansen WB, et al: Effects of program implementationon adolescent drug use behavior: The Midwestern Prevention Project. Evaluation Review. 1990, 14:264-289. (10) Perry CL, Grant M, Ernberg G, et al: W.H.O. collaborative study on alcohol education and young people: Outcomes of a four-country pilot study. International Journal of the Addictions. 1989, 24: 1145-1171.
Klepp et al. (11) Jacobs DR, Luepker RV, Mittelmark MB, et al: Community-wide prevention strategies: Evaluation design of the Minnesota Heart Health Program. Journal of Chronic Disease. 1986, 39.'778-788. (12) Mittelmark MB, Luepker RV, Jacobs DR, et al: Communily-wide prevention of cardiovascular disease: Education strategies of the Minnesota Heart Health Program. Preventive Medicine. 1986, 15: 1-17. (13) Perry CL, Kelder SH, Murray DM, Klepp KI: Community-wide smoking prevention: Long-term outcomes of the Minnesota Heart Health Program and the Class of 1989 Study. American Journal of Public Health. 1992, 82:1210-1216. (14) Kelder SH, Perry CL, Klepp KI: Community-wide youth exercise promotion: Long-term outcomes of the Minnesota Heart Health Program and the Class of 1989 Study. Journal of School Health. 1993, 63:218-223. (15) Kelder SH, Perry CL, Lytle L, Klepp KI: Community-wideyouth nutrition education: Long-term outcomes of the Minnesota Heart Health Program and the Class of 1989 Study. Health Education Research (in press, 1995). (16) Perry CL, Klepp KI, Shulz JM: Primary prevention of cardiovascular strategies for youth. Journal of Consulting and Clinical Psychology. 1988, 56:358-364. (17) Perry CL, Klepp KI, Sillers C: Community-wide youth strategies for cardiovascular health: The Minnesota Heart Health Program Youth Program. Health Education Research. 1989, 4:87-101. (18) Perry CL, Baranowski T, Parcel GS: How individuals, environments, and health behavior interact: Social Learning Theory. In Glartz K, Lewis FM, Rimer BK (eds), Health Behavior and Health Education. San Francisco, CA: Jossey-Bass, 1990, 161-186. (19) BanduraA: Social Foundations of Thought and Action. Engiewood Cliffs, NJ: Prentice-Hall, 1986. (20) Johnston LD, O'Malley PM, Bachman JG: Drug Use Among American High School Seniors, College Students, and Young Adults, 1975-1990. Volume 1: High School Seniors, DHHS Publication No. (ADM) 91-1831, Washington, DC: U.S. Government Printing Office, 1991. (21) Klepp KI, Perry CL, Jacobs DR: Onset, development, and prevention of drinking and driving among adolescents. European Journal of Psychology of Education. 1987, 2:421-442. (22) Donnor A, Birkett N, Buck C: Randomization by cluster: Sample size requirementsand analysis. American JournalofEpidemiology. 1990, 114:906-914. (23) Zucker DM: An analysis of variance pitfall: The fixed effects analysis in a nested design. Educational Psychology Measures. 1991, 50:731-738. (24) SAS Institute, Inc.: SAS/STAT Users Guide: Volume 2, GLMVARcomp, Version6 (4th Ed.). Cary, NC: SAS Institute, Inc., 1989.
Knut-lnge Klepp, Ph.D. University o f Bergen, N o r w a y
Steven H. Kelder, Ph.D. University o f Texas Health Science Center at Houston Cheryl L. Perry, Ph.D. University o f Minnesota
ABSTRACT
1990 according to curriculum content. He concluded that C o m prehensive and Social Influence programs were most successful in preventing the onset o f substance use compared to other intervention techniques such as Information/Values Clarification, Affective Education, and Alternatives programs. Comprehensive and Social Influence programs are characterized b y a focus on teaching students about peer and other social pressures and developing skills to resist these pressures. The programs often include information about substance use, resistance skills training, pledges not to use substances and norm setting, a n d nearly all o f them feature peer leaders who assist with program delivery. The Comprehensive programs included a broader spectrum o f prevention strategies, including decision making, than did the Social Influence programs. A number o f recent Comprehensive and Social Influence programs have reported positive short-term results with respect to reduced onset o f alcohol and marijuana use (6-I0). While delaying the onset o f drug use among adolescents is a major goal o f such programs, reducing the long-term incidence o f drug-related injuries and chronic diseases is the ultimate goal. However, the long-term impact o f these educational programs on alcohol and marijuana use still remains to be seen. In this article we report on both the short-term and longterm results o f an educational program, "Shifting Gears," designed to reduce alcohol use, drinking and driving behavior, and marijuana use in a cohort o f high school students. "Shifting Gears" was implemented as part o f the Class o f 1989 Study, a substudy o f the Minnesota Heart Health Program (MHHP). M H H P is a population-wide research a n d demonstration project designed to reduce cardiovascular disease (CVD) in three educated communities (1980-1993). The education communities received five years o f M H H P community-wide risk reduction interventions including mass media, c o m m u n i t y organization, risk factor screening, adult education, and schoolbased youth interventions, and were compared to matched reference communities (11,12). M H H P focused on changes in cating habits, physical activity levels, cigarette smoking, and adberence to hypertension medication. The larger project did not seek changes in adolescent and adult alcohol or marijuana use. In the Class o f 1989 Study, students in the M H H P intervention c o m m u n i t y o f Fargo and West Fargo, N o r t h Dakota, and o f Moorhead, Minnesota, received school-based interventions designed to favorably influence their smoking, physical activity levels, and eating behaviors each year from 1983 to 1987. During the school year o f 1985-1986 when students were in ninth grade, the program, called "Shifting Gears," which
The Minnesota Heart Health Program (MHHP) is a population-wide research and demonstration project designed to reduce cardiovascular disease in three educated communities (19801993) compared to three matched reference communities. The Class of 1989 Study, a substudy of the MHHP, collected selfreported data in one educated and one matched reference community. All sixth graders enrolled in both communities were invited to participate in a baseline survey in 1983, and that grade cohort was surveyed annually throughout junior high and high school until 1989. Students received interventions designed to favorably influence their smoldng, physical activity levels, and eating behavior each year.from 1983 to 1987. As part of this five-year intervention, a program addressing smoldng, alcohol use, drinking and driving behavior, and marijuana use was implemented during the school year o f 1985-1986, when students were in ninth grade. Using the school as the unit o f analysis, we found that students in the intervention community in 1986 reported fewer occasions on which they had been drinldng alcohol in the past 30 days than did students in the reference community. Furthermore, students in the intervention community reported less problem drinldng in the previous two weeks and less driving after drinldng than did students in the reference community. These positive intervention effects were not maintained through twelfth grade. (Ann Behav Med
1995, 17(1):19-24)
INTRODUCTION Literature reviewing the impact o f educational programs designed to delay the onset o f alcohol and marijuana use among adolescents has often concluded that there is little or contradicting evidence regarding the effectiveness o f p r i m a r y prevention programs (1--4). In a recent review, Hansen (5) classified substance use prevention programs published between 1980 and
1 Preparation of this manuscript was supported in part by grant R01 HL 25523 from the National Heart, Lung and Blood Institute.
Reprint Address: C. L. Perry, Ph.D., Division of Epidemiology, School of Public Health, University of Minnesota, 1300 South Second Street, Minneapolis, MN 55454. 9 1995 by The Society of Behavioral Medicine. 19
20
ANNALS OF BEHAVIORAL MEDICINE
Klepp et al.
TABLE 1 The Class of 1989: Study Design Intervention Community (Fargo-Moorhead)
Reference Community (Sioux Falls)
Sixth grade 1982-1983
Baseline Survey I The Lunch Bag Program
Seventh grade 1983-1984
The Minnesota Smoking Prevention Program Survey II Health Olympics greeting card I
Survey II
Health Olympics greeting card II Survey III FM 250 physical activities challenge
Survey III
"Shifting Gears" Survey IV (Alcohol, marijuana use, drinking and driving questions added)
Survey IV
Eighth grade 1984-1985
Ninth grade 1985-1986
Baseline Survey I
Tenth grade 1986-1987
Slice of Life Survey V
Survey V
Eleventh grade 1987-1988
Survey VI
Survey VI
Twelt~h grade 1988-1989
Survey VII
Survey VII
[Reproduced with permission from Oxford University Press (Perry CL, Klepp K-I, Sillers C: Community-wideyouth strategies for cardiovascular health: The Minnesota Heart Health Program Youth Program. Health Education Research. 1989, 4:87-101).] addressed smoking, alcohol and marijuana use, and drinking and driving behavior, was implemented. This was done since smoking covaries with these behaviors, and it, therefore, seemed appropriate to address all of them in a school-based health program. Sioux Falls, South Dakota, served as the reference community. As has been reported elsewhere, students in the Fargo-Moorhead community reported significantly less smoking (13), more physical activity (14), and a more heart healthy diet (15) following the intervention than did students from Sioux Falls. These differences were maintained through the twelfth grade, and it was concluded that behavioral curricula in school, coupled with the supportive MHHP community-wide strategies, can produce lasting improvements in adolescent health-related behaviors. The maintenance of effects was particularly noteworthy compared with studies of school curricula alone. The alcohol and marijuana use school-based prevention program was not supported by the MHHP community-wide intervention strategies. Because of this, a unique opportunity was provided. In the present article we investigate whether students in Fargo-Moorhead reported less alcohol use, less drinking and driving, and less marijuana use than students from Sioux Falls following "Shifting Gears." In addition to assessing whether these behaviors changed after "Shifting Gears," we were able to examine the maintenance of effects to see if the results were similar to the other MHHP-targeted behaviors, where long-term maintenance was noted, or similar to other school curricula, where only short-term effects were seen. If the latter was observed, then further support for school curricula imbedded in community-wide efforts would be suggested, even though this study was not designed to directly address that question. METHODS Subjects Fargo--Moorhead and Sioux Falls, two of six MHHP communities, had been matched based on population size (about 100,000 each), socioeconomic makeup (primarily Caucasian and middle class), and distance from Minneapolis-St. Paul, Min-
nesota (250 miles). All sixth graders enrolled in Fargo-Moorhead and Sioux Falls were invited to participate in a baseline survey in April/May of 1983. This grade cohort was subsequently surveyed annually throughout high school, until graduating in 1989. From 1983 to 1986, 13 grade schools participated in the survey, and from 1987 to 1989 these same students went to 7 high schools (number of students per school ranged from 99 to 464). Participating students at baseline numbered 1,342 in the intervention community and 1,034 in the reference community. Response rates for the six follow-up periods were: 88%, 81%, 70%, 66%0, 59%, and 45%, respectively. Class of 1989 Education Class of 1989 students in Fargo--Moorhead participated in MHHP-sponsored health programs in school from sixth through tenth grade. An overview of the Class of 1989 design and educational programs is provided in Table 1. Details of the Class of 1989 school interventions and MHHP community interventions are described elsewhere (12-17). "Shifting Gears" was the only Class of 1989 or MHHP component addressing alcohol and marijuana use. Students in the reference city, Sioux Falls, did not receive any of the MHHP-sponsored community or school-based programs. Throughout the study period, these students received their school district's regular health curriculum. This curriculum did not contain any Comprehensive or Social Influence drug prevention programs. "Shifting Gears" "Shifting Gears" was a program designed to delay or prevent the onset of tobacco, alcohol, and marijuana use, and the content of the program followed a Social Influence model of intervention derived mainly from Social Learning Theory (18,19). The peer-led curriculum assumed that substance use is normative in American culture and serves a purpose for adolescents. As a result, the main emphasis of"Shifting Gears" was on why students begin to use these substances and to increase
Alcohol and Marijuana U s e Prevention their awareness that alternatives exist. Peer leaders assisted the teachers with group discussions and role play activities. The activities within "Shifting Gears" focused on building social skills enabling students to resist pressures to use drugs or engage in hazardous behaviors such as drinking and driving. The curriculum taught students how to critique and create mass media messages, thereby learning how the industry attempts to shape their behavior through advertising. Students produced storyboards for a video production which reflected their knowledge about the consequences of tobacco and alcohol use, what influenced them to use these substances, and pertinent skills and refusal techniques. A videotape was produced using the best storyboards from participating schools. Students from several schools acted in the videotape, which was then filmed and edited professionally and shown to all participating ninth grade classes. "Shifting Gears" was concerned with the functional meaning of adolescent drug use, and activities were designed to provide knowledge of health-enhancing alternative activities that serve similar functions for adolescents. The program focused on providing credible positive role models and setting a norm of non-drug use. Finally, "Shifting Gears" encouraged the practice of refusal and alternative skills via role playing and provided incentives and positive reinforcement for those alternative behaviors. A n outline of the intervention activities is presented in Table 2.
Outcome Evaluation Outcome evaluation was conducted through an annual survey completed by the students in their health, social science, or English classes. All students in the relevant grade level in school on a particular day were tested. Each year, starting in 1983, students were asked if they had ever had a drink of alcohol outside of church. Other measures of students' alcohol consumption, drinking and driving behaviors, and marijuana use were assessed annually beginning in the spring of 1986 (i.e. after the implementation of"Shifting Gears"). These measures were taken from the Monitoring the Future Study (20) and a Minnesota survey on drinking and driving behavior (21). They have all been found to have a high degree of reliability and validity when employed in studies of high school populations, and include: Alcohol Consumption: " O n how m a n y occasions have you had alcoholic beverages to drink during the last 30 days" (1 = 0 occasions; 7 = 40 occasions or more); "How many times have you had five or more drinks in a row (problem drinking) over the last two weeks" (recoded so that 0 ffi none; 100 ffi once or more often); Drinking andDriving Behavior: "During the past three months, how often have you had two or more drinks on a single occasion prior to driving a motor vehicle" (recoded so that 0 ffi none; 100 ffi once or more often); "During the past three months, how often have you had five or more drinks on a single occasion prior to driving a motor vehicle" (recoded so that 0 = none; 100 = once or more often); and Marijuana Use: "Have you ever tried marijuana" (0 = never; 1 ffi once; 2 = more than once); "During the last three months, how often have you used marijuana" (1 = never; 8 ffi every day). Other relevant measures were: age at the time of the survey, gender, and parental occupation categories.
Analysis Methods In this study, we employed a nested cohort design where whole cities were assigned to conditions. As subjects from a single community tend to be more like one another than they
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TABLE 2
"Shifting Gears": Summary of Intervention Activities Session 1: Teacher introduces the program. Students view a video on alcohol abuse and evaluate its effectiveness (peer-led small group discussion). Homework assignment: Read a "Video Guide" to prepare them to begin their own video production. Session 2: Discussion of negative consequences associated with people their age using alcohol (teacher-led) and reasons why people start drinking (peer-led). Complete a video pre-production worksheet determiningtarget audience and objectives for the video (peer-led). Homework assignment: Outline a realistic situation involvingalcohol use which someone their age could encounter. Session 3: Discuss situations involving alcohol use and identify positive, alternative ways of dealing with them. Select one situation for the video story board (peer-led). Discuss effective techniques to deal with difficult situations includingalcohol (peer-led). Complete and discuss a survey on drinking and driving related issues (teacher-led). Homework assignment: Bring to class two advertisements in which alcohol is being sold. Session 4: Presentation on different types of pressure used to influence people to use drugs or drink and drive (teacher-led). Analyze the role of driving in students' life (teacher-led). Identify possible alternatives or coping strategies that can be used in situations where someone feels pressured to use alcohol or drink and drive. Develop video story boards identifying types of pressures being exercised (peer-led). Homework assignment: Read the "Video Guide" about how their video will be produced. Session 5: Analyze and identify advertising pressure to use alcohol (teacher-led). Final development of each small group's video presentation. Session 6: Class presentations (role play) of video story boards. Class vote to select the presentation students feel would be the most effective in preventing alcohol use or drinking and driving in people their age.
are like subjects in the other community, the within-community correlation in the data, indexed by the community-level intraclass correlation coefficient (ICC), adds an additional component of the variability to the intervention group means above and beyond that attributable to either the individual subjects or the interventions themselves (22). Unless this component is accounted for in the analysis, the evaluation of the intervention effects will be positively biased in proportion to the magnitude of the ICC and the n u m b e r of respondents in each c o m m u n i t y (23). In the present study, students were observed in classrooms, which were nested within schools, which were nested within the towns assigned to the two treatment conditions. ICC, which reflects the within-unit correlation in the data at each level of nesting, also captures the within-unit correlation at all levels of nesting lower in the hierarchy. Thus, while we could not use the c o m m u n i t y as the unit of analysis, we could correct for most of the variance inflation expected in such a design by using the school. This was accomplished for the data gathered after 1985 using PROC GLM in SAS (24), in which a model that used the individual's response as the outcome and included school as a nested random effect was fit for each round of data; the intervention effect was tested against the school variance. Separate analyses were performed at each follow-up round. Only those
22
ANNALS OF BEHAVIORAL MEDICINE
Klepp et al. 55
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FIGURE 1: Reported number of drinking occasions (1 7 = 4 0 or more) during past 30 days.
=
RESULTS By the onset of the study in 1983, 53% of all the students reported having had at least one drink. This proportion increased rapidly over the years, and in 1989, 92% of participating students reported having been drinking at least once. There was no significant difference in lifetime prevalence of alcohol consumption between the intervention and reference communities throughout the study. We did, however, observe that in 1986, following the "Shifting Gears" intervention, ninth grade students in the intervention community reported significantly fewer drinking occasions "during the last 30 days" (Figure 1) and fewer occasions of problem drinking (five or more drinks) (Figure 2), than did students in the reference community. The point estimates remained lower in the intervention community from tenth to twelfth grade, but were not significantly different, and the differences became smaller each year (Figures 1, 2). A similar pattern was observed for drinking and driving behavior. While ninth grade students following the intervention reported significantly fewer drinking and driving occasions "during the last three months" than did students in the reference community, these differences were not maintained over time
lOth
'11th
' 12th
.293
.310
.551
F I G U R E 2: Proportion of students reporting having had five or more drinks in a row during the last two weeks, by grade.
0;
students who participated in the baseline survey and any subsequent round of follow-up were included in the analysis, excluding those new to the community following baseline. All analyses included covariance adjustments for age and sex, and in tenth through twelfth grade, adjustments were made for parental job class. As measures of students' alcohol consumption, drinking and driving behaviors, and marijuana use were ineluded for the first time in the spring of 1986 (ninth grade), we were not able to make adjustments for the baseline or the eighth grade values of the dependent variables. Adjusted proportions or mean levels for the dependent variables, p-values, and 95% confidence intervals are presented. The confidence intervals and p-values for each follow-up period refer to comparisons between the intervention and reference conditions. Figure l also presents the degrees of freedom associated with each p-value and these remain the same for all subsequent figures.
9t'h
.028
(Figures 3, 4). By twelfth grade, 35% of participating students reported having driven a motor vehicle after having had t w o or more drinks on a single occasion "within the past three months." Finally, there were no significant differences between students from the two communities regarding lifetime prevalence of marijuana use or reported frequency of marijuana use "during the past three months." We observed, however, the same pattern as for alcohol use and drinking and driving, with students from the intervention communities reporting lower use rates than students from the reference communities, differences which dedined over time (Figure 5). Attrition Analysis Financial constraints precluded any attempts to contact those students who had moved out of the community, were absent, involved in work-study, or had dropped out and were not present in the class the day of the survey. The response rates were approximately equal by community with the exception of the 40 . . . . e ....
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lOth .274
l'lth .630
,
~
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30
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9th .013
112th .666
FIGURE 3: Proportion of students reporting having had two or more drinks prior to driving during the past three months.
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=-
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9tl~ .009
lOth .142
11t" .420
~12th .713
F I G U R E 4: Proportion of students reporting having had five or more drinks prior to driving during the past three months.
last year of data collection where 55% of the intervention community students were surveyed compared to 31% in the reference community. The lower response rate in the reference group in the last year was primarily due to higher absenteeism during the survey period. For example, a senior "ditch day" occurred resulting in a large number of absentees on one of the scheduled survey days. The extent of attrition bias was approximated by identifying those missing in any given year and examining their previous year's alcohol use, drinking and driving involvement, and marijuana use. Those missing and identified the previous year were then compared to those students who were present both years. Students not present at any follow-up had a previous year value indicating that they drank alcohol, smoked marijuana, and drank before driving more often than did those students present both years. With the exception of tenth grade frequency of alcohol use and marijuana use, the differences between those missing and those present by community were not significant. This attrition bias, including the significant differences observed for tenth grade, tended to underestimate the intervention effects; that is, intervention effects may have been larger if the missing students had been recontacted. However, they still would not have been sulficient to change the lack of significance of the differences reported. Again, since we lack data for the dependent variables for eighth grade, we were not able to see what impact attrition might have had on the ninth grade values. DISCUSSION Results from this study support findings from previous studies indicating that school-based programs utilizing a Social Influence model of intervention may contribute in deterring the onset of alcohol use. Students from the Fargo-Moorhead community exposed to the "Shifting Gears" program reported, in 1986, fewer occasions on which they had been drinking alcohol in "the past 30 days," less problem drinking in "the previous two weeks" (i.e. drinking five or more drinks in a row), and less drinking and driving than did students from Sioux Falls. These differences, however, were not maintained over time and had
p-value
9th .096
l'Oth .124
'11th .270
112th .281
F I G U R E 5: Reported ever having tried marijuana (0 -- no; 1 ffi once; 2 ffi at least twice).
mostly disappeared by twelfth grade. A similar pattern, although non-significant, was seen for marijuana use. The positive intervention effects observed in the Class of 1989 Study with respect to smoking, physical activity levels, and heart healthy eating were maintained throughout high school (13-15). In contrast to students' smoking, physical activity levels, and eating behavior, the alcohol, drinking and driving, and marijuana resistance skills were not reinforced through multiple school-based interventions or by community-wide educational programs. This may explain the lack of long-term intervention impact for alcohol use and drinking and driving behavior. Thus, these results, although speculative, suggest the need for behavior-specific interventions and for consistent community-based interventions in order to achieve and maintain effects. As the Class of 1989 Study was designed to assess changes in CVD risk-related factors, frequency measures of alcohol use, drinking and driving behavior, and marijuana use were first included in the 1986 survey. Thus, we lack baseline data prior to implementing the "Shifting Gears" program, and the observed 1986 intervention effects should therefore be interpreted with caution. Each year, starting in 1983, students were, however, asked if they had ever had a drink outside church. We observed no significant difference in baseline lifetime prevalence of alcohol use. Thus, we conclude that a plausible interpretation is that the intervention effect observed in 1986 is a result of the Class of 1989 intervention. The Class of 1989 Study was designed and implemented when common research practice utilized the individual as the unit of analysis. The analyses presented in this paper, however, were conducted with the school as the unit of analysis, tending to provide a more conservative estimate of the error variance. The degrees of freedom available for 1983-1986 were df ffi 1,11 and from 1987-1989 d f = 1,5. Thus, the intervention outcomes must be considered in light of low statistical power to detect a difference, particularly in the last three years, as graphically illustrated by the wide confidence intervals in the figures. Low statistical power strengthens our conclusions for significant findings immediately following "Shifting Gears," and allows for speculative interpretation of marginally significant results such as those for marijuana (i.e. p-values of -< . 10).
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ANNALS OF BEHAVIORAL
MEDICINE
CONCLUSION In contrast to its impact on CVD risk factors, positive intervention effects with respect to alcohol use and drinking and driving behavior were not maintained over time following the Class of 1989 Study intervention program. This finding points to the need for further investigation of the potential interaction of school-based health promotion programs with supportive community-wide strategies in order to produce lasting improvements in adolescent health-related behaviors.
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Klepp et al. (11) Jacobs DR, Luepker RV, Mittelmark MB, et al: Community-wide prevention strategies: Evaluation design of the Minnesota Heart Health Program. Journal of Chronic Disease. 1986, 39.'778-788. (12) Mittelmark MB, Luepker RV, Jacobs DR, et al: Communily-wide prevention of cardiovascular disease: Education strategies of the Minnesota Heart Health Program. Preventive Medicine. 1986, 15: 1-17. (13) Perry CL, Kelder SH, Murray DM, Klepp KI: Community-wide smoking prevention: Long-term outcomes of the Minnesota Heart Health Program and the Class of 1989 Study. American Journal of Public Health. 1992, 82:1210-1216. (14) Kelder SH, Perry CL, Klepp KI: Community-wide youth exercise promotion: Long-term outcomes of the Minnesota Heart Health Program and the Class of 1989 Study. Journal of School Health. 1993, 63:218-223. (15) Kelder SH, Perry CL, Lytle L, Klepp KI: Community-wideyouth nutrition education: Long-term outcomes of the Minnesota Heart Health Program and the Class of 1989 Study. Health Education Research (in press, 1995). (16) Perry CL, Klepp KI, Shulz JM: Primary prevention of cardiovascular strategies for youth. Journal of Consulting and Clinical Psychology. 1988, 56:358-364. (17) Perry CL, Klepp KI, Sillers C: Community-wide youth strategies for cardiovascular health: The Minnesota Heart Health Program Youth Program. Health Education Research. 1989, 4:87-101. (18) Perry CL, Baranowski T, Parcel GS: How individuals, environments, and health behavior interact: Social Learning Theory. In Glartz K, Lewis FM, Rimer BK (eds), Health Behavior and Health Education. San Francisco, CA: Jossey-Bass, 1990, 161-186. (19) BanduraA: Social Foundations of Thought and Action. Engiewood Cliffs, NJ: Prentice-Hall, 1986. (20) Johnston LD, O'Malley PM, Bachman JG: Drug Use Among American High School Seniors, College Students, and Young Adults, 1975-1990. Volume 1: High School Seniors, DHHS Publication No. (ADM) 91-1831, Washington, DC: U.S. Government Printing Office, 1991. (21) Klepp KI, Perry CL, Jacobs DR: Onset, development, and prevention of drinking and driving among adolescents. European Journal of Psychology of Education. 1987, 2:421-442. (22) Donnor A, Birkett N, Buck C: Randomization by cluster: Sample size requirementsand analysis. American JournalofEpidemiology. 1990, 114:906-914. (23) Zucker DM: An analysis of variance pitfall: The fixed effects analysis in a nested design. Educational Psychology Measures. 1991, 50:731-738. (24) SAS Institute, Inc.: SAS/STAT Users Guide: Volume 2, GLMVARcomp, Version6 (4th Ed.). Cary, NC: SAS Institute, Inc., 1989.
