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Paradoxical effects of blood alcohol concentration charts
PREVENTIVE
MEDICINE
20,
43143.5 (1991)
SHORT REPORT Paradoxical
Effects of Blood Alcohol
Concentration
Charts
C. ARTHURMYERS, D.O., M.P.H.,* MELBOURNE F. HOVELL, PH.D., M.P.H.,**’ JOHN P. ELDER, PH.D., M.P.H.,* AND JAMES A.HALL, PH.D.? *Graduate
School of Public Health and tSchoo1 of Social Work, San Diego State University, San Diego, California 92182
Background. This study was designed to determine the association between alcohol drinking and the possession of blood alcohol concentration charts. Method. A total of 30 college-age subjects participated in the study. Subjects were randomly assigned to either an experimental or a control group. All subjects answered a short entrance questionnaire to determine their height and weight. Those assigned to the experimental group were supplied a copy of a blood alcohol concentration chart and instructed in its use. The volume of alcoholic beverages consumed was surreptitiously counted for all subjects. prior to leaving the premises the subjects completed an exit questionnaire which asked them to estimate the amount of alcohol they had consumed, whether they had driven to the pub, and whether they intended to drive away. The time spent in the pub was noted for each subject. Resulrs. Among those in the control group there was a tendency to overestimate the volume consumed, and for those in the experimental group, a tendency to more accurately estimate their consumption. Those given blood alcohol concentration charts consumed alcohol at a signiticantly higher rate than did those in the control group. Conclusion. A likely explanation for this outcome is that the chart served as a stimulus to prompt a drinker to more quickly achieve a blood alcohol level consistent with his/her drinking expectancies. o 1991 Academic press, 1~.
INTRODUCTION
Alcohol is a major risk factor for motor vehicle crashes, with over 50% of vehicle fatalities in the United States being alcohol-related (1). Furthermore, most studies agree that those individuals 16-25 years of age are at particular risk for death and/or injury from drinking and driving (2). This association, as well as the nontraumatic adverse health effect of alcohol, has led to interventions to moderate alcohol drinking and/or driving under the influence (3). Some community-based campaigns have distributed blood alcohol concentration (BAC) nomograms designed to inform the drinker of unsafe blood alcohol levels and promote reduced alcohol drinking/driving rates (4). These devices give an estimate of BAC for number of drinks consumed in relation to body weight and drinking time. However, the few studies to date that have attempted to determine the effect of nomograms or charts have not used random assignment or have not isolated the effects of the devices specifically (4,5). This study evaluated ’ To whom reprint requests should be addressed at Division of Health promotion and Behavioral Science, Graduate School of public Health, San Diego State University, San Diego, CA 92182. 431 0091-7435191$3.00 Copyright 8 1991 by Academic Press, Ins. All rights of reproduction in any fom reserved.
432
MYERS
ET AL.
the effect of a blood alcohol concentration nomogram on alcohol consumption rate, using objective measures and a randomly assigned control group design. METHOD Thirty college students entering a pub participated. Fourteen were female (mean age 21.6 years, SD = 1.02) and 16 were male (mean age 23.6 years, SD = 3.61). Upon entering, all received a hand stamp confirming their legal drinking age. Female and male patrons were alternately asked if, for $4.00, they would participate. If subjects entered in a group, only one member of the group was invited. Few (~6) patrons declined. Subjects were asked if they intended to drink alcohol in the pub. Those answering yes were included in the study. All subjects were then assigned at random to either a control or an experimental group. The mean weight and height of the experimental subjects were 145.1 lb and 68 in., respectively, and those of the control subjects were 143.4 lb and 67.3 in., validating the random assignment. All subjects were given $2.00 after group assignment and informed that they would receive $2.00 when they completed an exit questionnaire. No names were requested and subjects were assured of anonymity. The experimental subjects were given the California Department of Motor Vehicle’s blood alcohol concentration chart and all were able to identify the section pertaining to them and to describe how to determine their BAC. Controls were not given the chart. Each subject was surreptitiously observed by a research assistant who counted the alcoholic beverages consumed. Only beer and wine were served and only one subject drank wine. Each half glass of beverage consumed was counted. Observers estimated counts if a glass was refilled other than when empty or half full. Observers remained as inconspicuous as possible, and all observations were carried out without the apparent knowledge of any subject. The recruiter was experimentally blind to group assignments. The observers were not told whether they were observing experimental or control subjects. Counting took place on Friday afternoons during one semester. Each observation period was preceded by a 20-min training session including review of definitions, demonstrations, and feedback for mock practice. Interrater reliability estimates were obtained for a sample (eight 15min periods across subjects and sessions) of the observations by having two observers concurrently tally drink counts of the same subjects. Mean percentage of exact agreement was 87.5 and resulted in a correlation of r = 0.88 (P < 0.005). When the subjects left the pub, they completed a questionnaire asking the following questions: How many glasses of beer did you drink here today? How many glasses of wine did you drink? Did you drive yourself here today? Do you intend to drive yourself away from here now? In addition, the exit time was recorded. Each subject was informed that the researchers would provide free transportation should the subject so desire. Control subjects were given a copy of the BAC chart (previously provided to the experimental subjects) at the time of completion of the exit questionnaire.
BLOOD
ALCOHOL
CONCENTRATION
CHARTS
433
RESULTS
Twenty-nine subjects consumed beer and one consumed wine. The wine was converted to beer equivalents as per the BAC chart (i.e., 4 oz of wine = 12 oz of beer). The experimental group consumed a mean volume of beer of 42.3 oz (SD = 14.68) per subject, over a mean time in the pub of 49.9 mm (SD = 23.97). The control group consumed a mean volume of beer of 36.3 oz (SD = 20.9) per subject over a mean time of 70.7 mm (SD = 44.7). The mean volume of beer consumed by experimental subjects was 40.8 oz (SD = 16.41)per 100lb of body weight per hour, while that consumed by the controls was 24.9 oz (SD = 11.2) per 100 lb per hour. Thus, the group given the BAC charts had a consumption rate 1.6 times that of the control group (t = 3.09, df = 28, P < 0.01) (see Fig. 1). Essentially the same results were obtained for females and males separately. Self-reported estimates of the volume of alcoholic beverages consumed were obtained from all experimental subjects and 12 of the control subjects. Two control subjects and 6 experimental subjects correctly estimated (within 5 oz or one-half glass) the amount consumed. Eight controls and 4 experimental subjects overestimated their consumption. Only one control subject compared with 5 experimental subjects madeunderestimations. The result indicated a tendency of the control group to overestimate their consumption but failed to reach statistical significance. The mean overestimation by the control subjects was 10.4oz (SD = 14.80). The mean for the experimental group was 0.2 (SD = 17.7) oz underestimation. Analysis showed a tendency for the experimental subjects to more accurately estimate the volume consumed (t = 1.70, df = 25, P = 0.10). Five experimental subjects indicated they had driven to the pub and all five intended to drive away. Four of those left with chart-indicated blood alcohol levels of over 0. lo%, a level listed on the chart as being “definitely illegal to drive.” The fifth subject’s BAC per chart was between 0.05 and O.lO%, defined on the chart 601
Consumption Rate (21 std. error)
L 505 r 40. 1
g 30. VI P 8 20. B lo-
DrlUOl
txpertmentat
Study groups
FIG. 1. Rate of alcohol consumption per 100 lb of body weight per hour for the experimental and control groups.
434
MYERS ET AL.
as “may be illegal.” Three subjects from the control group drove to the pub, and two stated they would not drive away. These two had blood alcohol levels of over 0.10% per the chart. The control subject driving away left with a BAC of between 0.05% and 0.10%. DISCUSSION
Although it is appealingto assumethat BAC charts moderate drinking behavior, this study demonstrated objectively that the charts were associatedwith increased alcohol consumption rate among student drinkers in a university pub. These results are credible given similar results reported by Geller and Russ (6), who demonstrated that self-monitoring may increase consumption. While it was possible for an observer to seea subject handling a BAC chart, any recording bias resulting from such knowledge would be likely to lead to an underrecording of consumption. Subjects were randomly assignedto the conditions and the randomization was validated as balancing the groups. This design should have eliminated all sources of sampling error. The chart may act as either a sensitizing cue or a self-monitoring tool to facilitate the achievementof a blood alcohol level that will fulfill the subjects drinking expectations. A consistent relationship has been demonstrated between alcohol consumption and drinking expectancies (7-12). These studies suggest that BAC charts may promote drinkers to more readily achieve a certain degree of impairment, i.e., “disinhibition.” This study demonstrated that the possessionof BAC charts, immediately preceding drinking, led to an increased alcohol consumption rate among college students. Moreover, 90% of this sample departed the pub with chart-estimated alcohol blood levels in excess of 0.05%; 70% left with levels in excess of 0.10%. The majority of these young adult drinkers consumed enough alcohol to impair function, including driving. These results raise questions about iatrogenic effects and the cost-to-benefit ratio for widespread distribution of BAC charts. The research should be replicated in studies that target college-age as well as older drinkers in varied settings. REFERENCES 1. National Highway Traffic Safety Administration. Fatal Accident Reporting System 1986. Washington, DC: U.S. Department of Transportation, 1988. 2. Guslield JR. Social and cultural contexts of the drinking-driving event. J Stud Alcohol 1985; Suppl. 10:70-77. 3. Geller ES, Elder, JP, Hovel1 M, Sleet D. Behavioral approaches to drinking-driving interventions. In: Advances in Health Education and Promotion. In press. 4. Worden JK, Flynn BA, Darwin GM, Waller JA, Haugh LD. Preventing alcohol-impaired driving through community self-regulation training. Am J Public Health 1989; 79:287-290. 5. Werch CE. Information on blood alcohol concentration: Evaluation of two alcohol nomograms. J Drug Educ 1988; 18:81-92. 6. Geller ES, Russ NW. Drunk driving prevention: Knowing when to say when. In: Alcohol Accidents, and Injuries. No. P-173. Warrendale, PA: Society of Automotive Engineers, 1986:109122. 7. Brown SA, Creamer VA, Stetson BA. Adolescent alcohol expectancies in relation to personal and parental drinking patterns. J Abnorm Psychol 1987; 96:117-121.
BLOOD
ALCOHOL
CONCENTRATION
CHARTS
435
8. Brown SA, Goldman MS, Christiansen BA. Do alcohol expectancies mediate drinking patterns of adults? J Consult Clin Psycho2 1985; 53512-519. 9. Brown SA, Goldman MS, Inn A, Anderson LR. Expectations of reinforcement from alcohol: Their domain and relation to drinking patterns. J Consult Clin Psycho1 1980; 48:419-426. 10. Christiansen BA, Goldman MS, Inn A. Development of alcohol-related expectancies in adolescents: Separating pharmacological from social-leaming influences. J Consult Clin Psycho1 1982; S&336-344. 11. Leigh BC. Beliefs about the effects of alcohol on self and others. J Stud Alcohol 1987;48~l67-475. 12. Marlatt GA, Rohsenow DJ. Cognitive processes in alcohol use: Expectancy and the balanced placebo design. In: Mello NK, Ed. Advances in Substance Abuse: Behavioral and Biological Research. Greenwich: JAI Press. 1980. Received May 15, 1990 Revised August 21, 1990 Accepted October 10, 1990
MEDICINE
20,
43143.5 (1991)
SHORT REPORT Paradoxical
Effects of Blood Alcohol
Concentration
Charts
C. ARTHURMYERS, D.O., M.P.H.,* MELBOURNE F. HOVELL, PH.D., M.P.H.,**’ JOHN P. ELDER, PH.D., M.P.H.,* AND JAMES A.HALL, PH.D.? *Graduate
School of Public Health and tSchoo1 of Social Work, San Diego State University, San Diego, California 92182
Background. This study was designed to determine the association between alcohol drinking and the possession of blood alcohol concentration charts. Method. A total of 30 college-age subjects participated in the study. Subjects were randomly assigned to either an experimental or a control group. All subjects answered a short entrance questionnaire to determine their height and weight. Those assigned to the experimental group were supplied a copy of a blood alcohol concentration chart and instructed in its use. The volume of alcoholic beverages consumed was surreptitiously counted for all subjects. prior to leaving the premises the subjects completed an exit questionnaire which asked them to estimate the amount of alcohol they had consumed, whether they had driven to the pub, and whether they intended to drive away. The time spent in the pub was noted for each subject. Resulrs. Among those in the control group there was a tendency to overestimate the volume consumed, and for those in the experimental group, a tendency to more accurately estimate their consumption. Those given blood alcohol concentration charts consumed alcohol at a signiticantly higher rate than did those in the control group. Conclusion. A likely explanation for this outcome is that the chart served as a stimulus to prompt a drinker to more quickly achieve a blood alcohol level consistent with his/her drinking expectancies. o 1991 Academic press, 1~.
INTRODUCTION
Alcohol is a major risk factor for motor vehicle crashes, with over 50% of vehicle fatalities in the United States being alcohol-related (1). Furthermore, most studies agree that those individuals 16-25 years of age are at particular risk for death and/or injury from drinking and driving (2). This association, as well as the nontraumatic adverse health effect of alcohol, has led to interventions to moderate alcohol drinking and/or driving under the influence (3). Some community-based campaigns have distributed blood alcohol concentration (BAC) nomograms designed to inform the drinker of unsafe blood alcohol levels and promote reduced alcohol drinking/driving rates (4). These devices give an estimate of BAC for number of drinks consumed in relation to body weight and drinking time. However, the few studies to date that have attempted to determine the effect of nomograms or charts have not used random assignment or have not isolated the effects of the devices specifically (4,5). This study evaluated ’ To whom reprint requests should be addressed at Division of Health promotion and Behavioral Science, Graduate School of public Health, San Diego State University, San Diego, CA 92182. 431 0091-7435191$3.00 Copyright 8 1991 by Academic Press, Ins. All rights of reproduction in any fom reserved.
432
MYERS
ET AL.
the effect of a blood alcohol concentration nomogram on alcohol consumption rate, using objective measures and a randomly assigned control group design. METHOD Thirty college students entering a pub participated. Fourteen were female (mean age 21.6 years, SD = 1.02) and 16 were male (mean age 23.6 years, SD = 3.61). Upon entering, all received a hand stamp confirming their legal drinking age. Female and male patrons were alternately asked if, for $4.00, they would participate. If subjects entered in a group, only one member of the group was invited. Few (~6) patrons declined. Subjects were asked if they intended to drink alcohol in the pub. Those answering yes were included in the study. All subjects were then assigned at random to either a control or an experimental group. The mean weight and height of the experimental subjects were 145.1 lb and 68 in., respectively, and those of the control subjects were 143.4 lb and 67.3 in., validating the random assignment. All subjects were given $2.00 after group assignment and informed that they would receive $2.00 when they completed an exit questionnaire. No names were requested and subjects were assured of anonymity. The experimental subjects were given the California Department of Motor Vehicle’s blood alcohol concentration chart and all were able to identify the section pertaining to them and to describe how to determine their BAC. Controls were not given the chart. Each subject was surreptitiously observed by a research assistant who counted the alcoholic beverages consumed. Only beer and wine were served and only one subject drank wine. Each half glass of beverage consumed was counted. Observers estimated counts if a glass was refilled other than when empty or half full. Observers remained as inconspicuous as possible, and all observations were carried out without the apparent knowledge of any subject. The recruiter was experimentally blind to group assignments. The observers were not told whether they were observing experimental or control subjects. Counting took place on Friday afternoons during one semester. Each observation period was preceded by a 20-min training session including review of definitions, demonstrations, and feedback for mock practice. Interrater reliability estimates were obtained for a sample (eight 15min periods across subjects and sessions) of the observations by having two observers concurrently tally drink counts of the same subjects. Mean percentage of exact agreement was 87.5 and resulted in a correlation of r = 0.88 (P < 0.005). When the subjects left the pub, they completed a questionnaire asking the following questions: How many glasses of beer did you drink here today? How many glasses of wine did you drink? Did you drive yourself here today? Do you intend to drive yourself away from here now? In addition, the exit time was recorded. Each subject was informed that the researchers would provide free transportation should the subject so desire. Control subjects were given a copy of the BAC chart (previously provided to the experimental subjects) at the time of completion of the exit questionnaire.
BLOOD
ALCOHOL
CONCENTRATION
CHARTS
433
RESULTS
Twenty-nine subjects consumed beer and one consumed wine. The wine was converted to beer equivalents as per the BAC chart (i.e., 4 oz of wine = 12 oz of beer). The experimental group consumed a mean volume of beer of 42.3 oz (SD = 14.68) per subject, over a mean time in the pub of 49.9 mm (SD = 23.97). The control group consumed a mean volume of beer of 36.3 oz (SD = 20.9) per subject over a mean time of 70.7 mm (SD = 44.7). The mean volume of beer consumed by experimental subjects was 40.8 oz (SD = 16.41)per 100lb of body weight per hour, while that consumed by the controls was 24.9 oz (SD = 11.2) per 100 lb per hour. Thus, the group given the BAC charts had a consumption rate 1.6 times that of the control group (t = 3.09, df = 28, P < 0.01) (see Fig. 1). Essentially the same results were obtained for females and males separately. Self-reported estimates of the volume of alcoholic beverages consumed were obtained from all experimental subjects and 12 of the control subjects. Two control subjects and 6 experimental subjects correctly estimated (within 5 oz or one-half glass) the amount consumed. Eight controls and 4 experimental subjects overestimated their consumption. Only one control subject compared with 5 experimental subjects madeunderestimations. The result indicated a tendency of the control group to overestimate their consumption but failed to reach statistical significance. The mean overestimation by the control subjects was 10.4oz (SD = 14.80). The mean for the experimental group was 0.2 (SD = 17.7) oz underestimation. Analysis showed a tendency for the experimental subjects to more accurately estimate the volume consumed (t = 1.70, df = 25, P = 0.10). Five experimental subjects indicated they had driven to the pub and all five intended to drive away. Four of those left with chart-indicated blood alcohol levels of over 0. lo%, a level listed on the chart as being “definitely illegal to drive.” The fifth subject’s BAC per chart was between 0.05 and O.lO%, defined on the chart 601
Consumption Rate (21 std. error)
L 505 r 40. 1
g 30. VI P 8 20. B lo-
DrlUOl
txpertmentat
Study groups
FIG. 1. Rate of alcohol consumption per 100 lb of body weight per hour for the experimental and control groups.
434
MYERS ET AL.
as “may be illegal.” Three subjects from the control group drove to the pub, and two stated they would not drive away. These two had blood alcohol levels of over 0.10% per the chart. The control subject driving away left with a BAC of between 0.05% and 0.10%. DISCUSSION
Although it is appealingto assumethat BAC charts moderate drinking behavior, this study demonstrated objectively that the charts were associatedwith increased alcohol consumption rate among student drinkers in a university pub. These results are credible given similar results reported by Geller and Russ (6), who demonstrated that self-monitoring may increase consumption. While it was possible for an observer to seea subject handling a BAC chart, any recording bias resulting from such knowledge would be likely to lead to an underrecording of consumption. Subjects were randomly assignedto the conditions and the randomization was validated as balancing the groups. This design should have eliminated all sources of sampling error. The chart may act as either a sensitizing cue or a self-monitoring tool to facilitate the achievementof a blood alcohol level that will fulfill the subjects drinking expectations. A consistent relationship has been demonstrated between alcohol consumption and drinking expectancies (7-12). These studies suggest that BAC charts may promote drinkers to more readily achieve a certain degree of impairment, i.e., “disinhibition.” This study demonstrated that the possessionof BAC charts, immediately preceding drinking, led to an increased alcohol consumption rate among college students. Moreover, 90% of this sample departed the pub with chart-estimated alcohol blood levels in excess of 0.05%; 70% left with levels in excess of 0.10%. The majority of these young adult drinkers consumed enough alcohol to impair function, including driving. These results raise questions about iatrogenic effects and the cost-to-benefit ratio for widespread distribution of BAC charts. The research should be replicated in studies that target college-age as well as older drinkers in varied settings. REFERENCES 1. National Highway Traffic Safety Administration. Fatal Accident Reporting System 1986. Washington, DC: U.S. Department of Transportation, 1988. 2. Guslield JR. Social and cultural contexts of the drinking-driving event. J Stud Alcohol 1985; Suppl. 10:70-77. 3. Geller ES, Elder, JP, Hovel1 M, Sleet D. Behavioral approaches to drinking-driving interventions. In: Advances in Health Education and Promotion. In press. 4. Worden JK, Flynn BA, Darwin GM, Waller JA, Haugh LD. Preventing alcohol-impaired driving through community self-regulation training. Am J Public Health 1989; 79:287-290. 5. Werch CE. Information on blood alcohol concentration: Evaluation of two alcohol nomograms. J Drug Educ 1988; 18:81-92. 6. Geller ES, Russ NW. Drunk driving prevention: Knowing when to say when. In: Alcohol Accidents, and Injuries. No. P-173. Warrendale, PA: Society of Automotive Engineers, 1986:109122. 7. Brown SA, Creamer VA, Stetson BA. Adolescent alcohol expectancies in relation to personal and parental drinking patterns. J Abnorm Psychol 1987; 96:117-121.
BLOOD
ALCOHOL
CONCENTRATION
CHARTS
435
8. Brown SA, Goldman MS, Christiansen BA. Do alcohol expectancies mediate drinking patterns of adults? J Consult Clin Psycho2 1985; 53512-519. 9. Brown SA, Goldman MS, Inn A, Anderson LR. Expectations of reinforcement from alcohol: Their domain and relation to drinking patterns. J Consult Clin Psycho1 1980; 48:419-426. 10. Christiansen BA, Goldman MS, Inn A. Development of alcohol-related expectancies in adolescents: Separating pharmacological from social-leaming influences. J Consult Clin Psycho1 1982; S&336-344. 11. Leigh BC. Beliefs about the effects of alcohol on self and others. J Stud Alcohol 1987;48~l67-475. 12. Marlatt GA, Rohsenow DJ. Cognitive processes in alcohol use: Expectancy and the balanced placebo design. In: Mello NK, Ed. Advances in Substance Abuse: Behavioral and Biological Research. Greenwich: JAI Press. 1980. Received May 15, 1990 Revised August 21, 1990 Accepted October 10, 1990