Measured Alcohol Content in College Party Mixed Drinks

Transcription

1 Psychology of Addictive Behaviors 2009 American Psychological Association 2009, Vol. 23, No. 1, X/09/$12.00 DOI: /a Measured Alcohol Content in College Party Mixed Drinks Nancy P. Barnett, Jill Wei, and Cristine Czachowski Brown University The main objective of this study was to measure the alcohol content in college party drinks. Samples of mixed drinks were collected from on-campus parties (N 23) over a 12-week period at a university in the Northeast. Samples were analyzed by using a method that measures oxygen utilization during ethanol oxidation. Standard drink equivalents were calculated and blood alcohol concentrations (BACs) for men and women were estimated. The percent alcohol in sampled drinks ranged from 3.7% to 22.8%. Characteristics of the sampled parties were not related to drink concentration. A party drink at the median concentration and drink size contained 0.97 standard drinks. Estimated BACs varied widely depending on drink alcohol concentration, but in most cases a heavy drinking episode for both men and women resulted in an estimated BAC at or above.08. Mixed drinks at the sampled parties on average approximated one standard drink, but the variability in mixed drink strength compromises a drinker s ability to keep track of the number of drinks consumed. Keywords: alcohol concentration, college parties, college student alcohol use Adults 18 to 24 years of age have the highest rates of alcohol use (Ham & Hope, 2003), with college students showing higher consumption than their noncollege peers (Johnston, O Malley, Bachman, & Schulenberg, 2007). Two of every five college students are heavy episodic drinkers, defined as having had five or more drinks in a row in the past 2 weeks for men and four or more for women (O Malley & Johnston, 2002). Heavy drinking puts students at risk for experiencing significant negative consequences, including unintentional injury, sexual assault, and death (Hingson, Heeren, Winter, & Wechsler, 2005). College presidents rank alcohol abuse as the number one problem on campus (Wechsler, 1996), and concern about heavy drinking among college students has led to national initiatives to reduce the prevalence of this behavior (National Institute of Alcohol Abuse and Alcoholism, 2002; U.S. Department of Health and Human Services, 2007). Drinking within the college environment typically occurs at bars and private parties (Clapp et al., 2000; Demers et al., 2002). Harford, Weschsler, and Seibring (2002) established that 64% to 85% of college students who drank in the past 30 days drank at the most recent party they attended, and 37% to 49% drank 5 or more drinks. Wechsler, Lee, Nelson, and Kuo (2002) compared student Nancy P. Barnett, Jill Wei, and Cristine Czachowski, Center for Alcohol and Addiction Studies, Brown University. Cristine Czachowski is now at Department of Psychiatry, Institute of Psychiatric Research, Indiana University School of Medicine, Indianapolis, Indiana. This study was supported in part by a Research at Brown grant from the Brown University Dean of the College to Jill Wei. The authors wish to thank Frances Mantak for research planning assistance, the Student Activities Office for information about campus parties, Geoff Gusoff for assistance with data collection, Suzanne Sales and Kelly Boyle for data analytic assistance, and Dr. Melissa Clark for helpful comments and advice. Address correspondence to Nancy P. Barnett, Center for Alcohol and Addiction Studies, Brown University, Box G-S121-5, Providence, RI nancy_barnett@brown.edu reports over multiple survey points and found no changes over time in student attendance at on-campus or dormitory parties, but a significant increase in any alcohol use and in heavy drinking at these on-campus venues over time. Drink Measurement An accepted definition for a standard drink is 12 oz. of beer (5% by volume), 5 oz. of wine (12% by volume), 1.5 oz. of liquor (40% by volume), or 1.5 oz. of liquor in a mixed drink (National Institute of Alcohol Abuse and Alcoholism, 2000). Although the size of a standard drink and the strength of different types of alcohol are well known in the beverage service industry and by alcohol researchers and educators, they may not be well known to the public. Studies have shown that college students are generally inaccurate in their estimate of alcoholic content of beverages (i.e., the amount of pure alcohol contained in a standard drink) and in their knowledge of national recommendations for low risk consumption (Hasking, Shortell, & Machalek, 2005; Martin, Liepman, Nirenberg, & Young, 1991). When asked to free-pour fluid into cups of various sizes to reflect what they perceived to be one beer, one shot, or the amount of liquor in one mixed drink, White, Kraus, McCracken, and Swartzwelder (2003) found that college students overpoured beer by 25%, shots by 26%, and mixed drinks by 80%. Alcohol-service parties are popular sources of alcoholic beverages for college students, and analyzing the content of mixed drinks served at these parties would provide basic information about the extent to which mixed drinks of this type reflect standard drink definitions, and would contribute an understanding of student alcohol consumption at these parties. Such information could be used to educate students about party drinks. The objectives of this study were to (1) measure the actual ethanol concentration of mixed drinks served at on-campus college parties; (2) establish whether party characteristics were related to measured drink strength; (3) calculate the number of standard drinks in one party drink at different measured concentrations; and (4) estimate the blood alcohol concentration (BAC) of drinkers consuming drinks of measured concentrations. 152

2 BRIEF REPORTS 153 Method Party Selection, Characteristics, and Attendance Procedures This study was conducted at a medium-sized private university in the Northeast. Alcoholic mixed drinks were sampled from registered and unregistered parties held on campus and hosted by university organizations or students. Registered events were social functions that required approval from the Student Activities Office, a license for alcohol service from the city, and specific training for party managers and bartenders. Registered parties were identified with assistance from the campus Student Activities Office. Unregistered parties were typically smaller functions that did not require campus registration. These were identified by posts on online event sites and word-of-mouth. A probability sampling approach was not used, because the number of parties of each type that would be held in the semester could not be anticipated. Therefore, attempts were made to sample as many parties as possible, while balancing the number of parties of each type. Sampling began the first weekend of the fall semester and continued for 12 weeks. The following characteristics of sampled parties were recorded: day of the week, week of the semester, whether the party was registered, whether there was a per drink charge, and whether there was posted information about the type(s) of alcohol available. A pair of researchers attended selected parties to record party characteristics and collect mixed drink samples. They did not reveal to party hosts or other party attendees that they were observing and collecting data. The researchers did not prepare or consume any alcoholic drinks. None of the parties had professionally trained bartenders; a student bartender prepared all drinks. Student bartenders at registered parties were party hosts who were required to complete a training session in which they learned about bartender liability, how to identify intoxication, and how to set up a bar (e.g., so individuals are not served more than one drink at a time), but were not trained in drink measurement. Sample Collection Two samples were collected at each party from different drinks at different times to prevent obtaining samples from the same common container and, if possible, from the same server. Samples that were mixed in advance and available to attendees were not selected if they had ice, and drinks that were prepared on request were ordered without ice to make estimations of drink size more straightforward. Samples were not collected from mixed drinks with particulates such as fruit, as this would disrupt the measurement of the alcohol concentration. Researchers transferred samples from the drink cups to airtight plastic vials (1.5 ml) with sealed tops in a private location (e.g., bathroom). Each sample was coded according to sample number (1 or 2), time of collection, whether the sample was premixed or prepared on request, and estimated number of ounces of drink in the cup. Because it was critical that sample collection be conducted without the knowledge of party hosts, measurement of the number of ounces per cup was estimated rather than measured directly. Parties on the surveyed campus typically use one of three sizes of party cups (small clear plastic cups [7 oz.], medium [12 oz.] Solo party cups, or large [16 oz.] Solo party cups). Researchers knew the number of ounces in each of these cups and estimated and agreed on the number of ounces of fluid in the cup based on the known size of cup. Immediately after the party, the samples were stored in a freezer until analysis. Ethanol Concentration Analysis Samples were analyzed using the AM1 Analyser (Analox Instruments, Lunenburg MA). The ethanol concentrations were determined with an amperometric oxygen electrode that measured oxygen consumption during the enzymatic oxidation of alcohol to acetaldehyde (the amount of oxygen necessary to break down ethanol is directly proportional to the alcohol concentration). The analyzer was first calibrated with a standard (200 mg% ethanol), and samples were diluted as necessary to read within 100 mg% of the standard. This translated to dilutions ranging from 1:10 (i.e., one part sample and nine parts sterile water) to 1:80. The mg% values were then converted to % alcohol by volume to conform to the measure generally used for commercial labeling and common to the public. Conversion of Party Drinks to Standard Drinks and Estimation of BAC Party drink sizes were converted into standard drink units by multiplying the sample concentration by the number of ounces in the party drink and dividing by 0.6 (the volume of fluid ounces of ethanol in a standard drink). Estimated BAC (Matthews & Miller, 1979) was calculated for the average size man and woman for low, medium, and high alcohol concentration ranges, for different volumes of alcohol consumed (1 to 10 party cups). The formula is [(drinks/2) (GC/W)] (.017 H), where drinks reflects the number of standard drink units consumed (converted as described earlier), GC reflects the gender constant of 7.5 for men and 9.0 for women, W reflects weight in pounds,.017 reflects the metabolism rate, and H reflects hours of drinking. We used 50th percentile body weights of 156 lbs. for a 20-year-old man and 128 lbs. for a 20-year-old woman (Kuczmarski et al., 2000). Two survey studies recently conducted with students at the same university both found the median length of time of a typical drinking episode was 2 hours (Barnett, 2008; Wei, Clark, & Barnett, under review), so for the estimations of BAC we assumed a 2-hour drinking period. Results Samples were collected on eight weekends over 12 weeks of the semester. No samples were collected on the other four weekends due to holidays or no identified parties with alcohol. A total of 23 parties were identified, and two samples were collected at each for a total of 46 samples. There was no indication at any time that the general student body or any party hosts were aware of the study. All samples were collected on a Friday or Saturday between 10:45 p.m. and 12:45 a.m. 1 Twelve parties (52.2%) were registered with the college. Review of party registration records showed that 36 parties were registered that semester, so one-third of these parties were sampled. Of all sampled parties, 12 (52.2%) had a per-drink charge, and 15 (65.2%) posted information about the alcohol in the 1 Some samples were collected after the midnight hour but were coded as being collected on the day the party started.

3 154 BRIEF REPORTS mixed drinks. There was almost complete overlap between registered parties and those with a per-drink charge; 91.7% of registered parties had a per-drink charge, compared with only 9.1% of the unregistered parties, 2 (1, N 23) 15.68, p.001. Given this overlap, no further analyses were conducted on per-drink charges. There was no relation between party registration and posting information about alcohol type; 58.3% of registered parties and 54.5% of nonregistered parties posted information, 2 (1, N 23) 0.03, nonsignificant (ns). Approximately half (n 11; 47.8%) of the sampled drinks were already mixed; the rest were prepared on request. There was no difference in preparation approach by registration status, 2 (1, N 23) 1.11, ns. Only one drink was not selected because it contained fruit. Alcohol Concentration of Samples The mean percent alcohol for sample 1 was 8.23% (SD 4.66%, median 6.90%, range 4.60% to 22.80%); the mean percent alcohol for sample 2 was 7.83% (SD 4.14%, median 6.70%, range 3.70% 19.70%). A paired samples t test on the two samples was nonsignificant, t(22) Given the lack of differences between samples 1 and 2, their average value (M 8.03%, SD 3.90%, median 6.85%, range 4.35% 20.10%) was used in subsequent analyses. Week of the semester was not significantly related to sample concentration (r.39, p.07). The concentrations of samples collected on Fridays (n 10; M 9.39%, SD 5.00%) and Saturdays (n 13; M 7.00%, SD 2.54%) were not significantly different, t(21) 1.38, ns, although the effect size of this difference was large (Cohen s d.61). No significant difference in sample concentration was found between registered (n 12; M 8.40%, SD 4.46%) and unregistered parties (n 11; M 7.64%, SD 3.35%), t(21) 0.45, ns, Cohen s d.19. The parties that posted information about the type(s) of alcohol being served (n 15; M 8.61%, SD 4.79%), and those that did not (n 8; M 7.29%, SD 2.34%), had significantly different variances so a t-test for unequal variances was conducted, t(18.24) 0.87, ns, Cohen s d.34. Alcohol concentration between premixed (M 7.26%, SD 2.75%) and prepared on request (M 8.74%, SD 4.73%) samples did not differ, t(21) 0.90, ns, Cohen s d.38. Estimated Volume of Drinks Sampled drinks contained an average of 9.26 oz. (274 ml) for sample 1 (SD 2.18, median 10, range 4 12) and 8.59 oz. (254 ml) for sample 2 (SD 2.61, median 9, range 3 12), a nonsignificant difference, t(21) The average volume across samples was 8.86 oz. (262 ml) (SD 2.10, median 8.5). Drink size was significantly and negatively related to alcohol concentration, r.45, p.05. Conversion to Standard Drinks and Estimation of BAC Given the wide range of concentrations and the negative association between concentration and drink size, we divided the concentration values into three ranges of low (n 8), medium (n 8) and high (n 7). Table 1 shows the conversion of 1 party cup to standard drink units using the average concentration and Table 1 Conversion of Party Drinks to Standard Drink Units at Low, Medium, and High Concentrations Low (n 8) Medium (n 8) High (n 7) Alcohol concentration 5.36% 6.87% 12.42% Party drink volume 9.56 oz oz oz. Standard drink units average drink sizes in the low, medium, and high ranges of concentration. Using the three ranges of average drink sizes, one party drink was the equivalent of 0.85 to 1.61 standard drinks. Using all samples combined, the median drink size of 8.5 oz. and the median concentration of 6.85% for all samples, the standard drink unit equivalent was The estimated BACs for men and women for the lowest, medium, and highest average concentration ranges are presented in Figure 1. Projected BACs for a heavy drinking episode of 4 drinks for women and 5 drinks for men at the three concentrations ranged from.086 to.193 for the average size woman and.069 to.160 for the average size man. Discussion This study is the first, to our knowledge, to analyze actual mixed drink samples from on-campus college parties. The majority of mixed drinks sampled had alcohol concentrations that were between beer (5%) and wine (12%), and the average value of 8.03% was in the range for the concentration of premixed cocktails (8% 9%; Kerr, Greenfield, & Tujague, 2006). A few of the samples were very strong relative to the average; the highest measured concentration was 22.8%, which is half as strong as liquor (80 proof; 40%). The median concentration drink in a median size cup closely reflected one standard drink unit. However, because concentrations had a wide range, the variation in standard drink units also ranged widely, indicating individual drinkers consuming the same volume in ounces of the measured concentrations would vary a great deal in the number of standard drinks consumed. The range of alcohol concentration in sampled drinks may make it very difficult for students to accurately count drinks and anticipate the effect of the consumed alcohol. We showed how the range of alcohol concentrations in sampled drinks is reflected in a wide range of estimated BACs for men and women. For example, an average size man could consume from approximately 1.5 to 7.5 cups of the median size drink (8.5 oz.), depending on the concentration level of the drink, to reach an estimated BAC of.08%. We did not find any of our measured party characteristics to be related to higher concentrations. However, some statistical relationships approached significance and warrant further consideration. Specifically, the negative correlation between alcohol concentration and week of the semester approached significance ( p.07), and the difference between Friday and Saturday night samples was not statistically significant but had a large effect size. Both of these analyses might reach statistical significance in a larger sample. These findings indicate that drink strength may be higher earlier in the semester and earlier in the weekend, which

4 BRIEF REPORTS 155 Panel A estimated BAC Drink Concentration 12.42% 6.87% 5.36% Number of Cups of Mixed Party Drink Panel B estimated BAC Drink Concentration 12.42% 6.87% 5.36% Number of Cups of Mixed Party Drink Figure 1. (A) Estimated blood alcohol concentration (BAC) for a 128-lb woman drinking over two hours for three ranges of alcohol concentration. (B) Estimated blood alcohol concentration for a 156-lb man drinking over two hours for three ranges of alcohol concentration. Cup size was the average volume for party drinks within each concentration range. The vertical line denotes a heavy drinking episode. might reflect student interest in getting more intoxicated after a period of lower consumption (i.e., summer, weekdays). Limitations We were unable to predict how many registered and unregistered parties there would be in the semester, so we did not collect a probability or random sample, but tried to sample as many parties as possible. Because college authorities do not monitor unregistered events, there is no way to estimate the number of unregistered parties in the sampled semester, and we are therefore unable to evaluate whether balancing the parties according to registration status biased the sample. However, because we did not establish any differences between registered and unregistered parties, and the t values for these comparisons were very low, we would not anticipate that applying (as yet unknown) weights to address sampling error would change our findings. Drink sizes were estimated by researchers, and we do not have an estimate of the reliability of this approach; this was an exploratory study in which it was important to not disclose the data collection process to party hosts, but a more precise measurement method or reliability estimates would be critical for future studies. Samples from other types of drinks (beer, wine) were not collected, but their concentration and volume measurement is more standardized. Samples that contained particulates were excluded and drinks did not contain ice. It is not known whether these drinks would differ in alcohol concentration. For the BAC estimations we used the national 50th percentile for weight and assumed a 2-hour drinking period based on data about the drinking behavior of students at the university. Although these are justifiable assumptions, others would yield different results. It is likely that drinkers adjust how many mixed drinks they consume such that they drink a smaller amount of higher concentration drinks; measuring the actual BACs of drinkers would be necessary to establish whether stronger drinks are associated with higher BACs. Finally, results from this study may not generalize to off-campus parties or to college campuses with different service and party policies.

5 156 BRIEF REPORTS Implications for Prevention, Policy, and Future Research Information from this study may be useful for education efforts and for establishing policies about alcohol service at college parties. Informing students about the variability in mixed drinks and that it is difficult to keep accurate track of the number of drinks when the alcohol concentration is unknown may raise awareness and reduce the possible risks associated with consuming mixed party drinks. Unfortunately, there are no known predictors of parties that serve higher strength drinks, making it difficult to inform party hosts and attendees about party types or server practices that are related to greater risk. In this study the bartenders were not professionally trained; they were college students trained in party management but not in drink preparation. Training in drink measurement for student bartenders may reduce the variation in ethanol content in mixed drinks. Without such training, our findings indicate that students may not consistently know how to prepare mixed drinks that are equivalent to standard drink units. The general student body may also benefit from education about alcoholic drinks, including education about standard drink measurement and alcohol concentration in different types of alcohol. Women may require specific education about the risks associated with drinking mixed drinks, given the potential for women to reach higher BACs and the evidence that women are less knowledgeable about drink strength (Martin et al., 1991). Additional research on alcohol content in party drinks is needed, including information about college party attendance and alcohol service, and on the prevalence of different types of drink service. Given the relatively small number of samples and the short time frame of sample collection, recording host characteristics (e.g., Greek status) in this study might have identified individual organizations; larger studies could establish whether particular groups on campus have different party drink strength. Finally, it is not known how well students are able to estimate the strength of mixed drinks. Comparing actual alcohol concentration to student predictions could provide information that could be useful in prevention programming. References Barnett, N. P. (2008). [Length of typical drinking episodes in college students]. Unpublished raw data. Clapp, J. D., Lange, J., Wong, M. J., Shillington, A., Johnson, M., & Voas, R. (2000). Deconstructing contexts of binge drinking among college students. American Journal of Drug and Alcohol Abuse, 26, Demers, A., Kairouz, S., Aldaf, E., Gliksman, L., Newton-Taylor, B., & Marchand, A. (2002). Environmental management: A comprehensive strategy for reducing alcohol and other drug use among Canadian undergraduates. Social Science and Medicine, 55, Ham, L. S., & Hope, D. A. (2003). College students and problematic drinking: A review of the literature. Clinical Psychology Review, 23, Harford, T. C., Weschsler, H., & Seibring, M. (2002). Attendance and alcohol use at parties and bars in college: A national survey of current drinkers. Journal of Studies on Alcohol, 63, Hasking, P., Shortell, C., & Machalek, M. (2005). University students knowledge of alcoholic drinks and their perception of alcohol-related harm. Journal of Drug Education, 35, Hingson, R., Heeren, T., Winter, M., & Wechsler, H. (2005). Magnitude of alcohol-related mortality and morbidity among U.S. college students ages 18 24: Changes from 1998 to Annual Review of Public Health, 26, Johnston, L. D., O Malley, P. M., Bachman, J. G., & Schulenberg, J. E. (2007). Monitoring the future national survey results on drug use, Volume II: College students and adults ages (NIH Publication No ). Bethesda, MD: National Institute on Drug Abuse. Kerr, W. C., Greenfield, T. K., & Tujague, J. (2006). Estimates of the mean alcohol concentration of the spirits, wine, and beer sold in the United States and per capita consumption: Alcoholism: Clinical and Experimental Research, 30, Kuczmarski, R. J., Ogden, C. L., Grummer-Strawn, L. M., Flegal, K. M., Guo, S. S., Wei, R., et al. (2000). CDC growth charts: United States. Advance data from vital and health statistics; no Hyattsville, MD: National Center for Health Statistics. Retrieved September 10, 2007, from Martin, C. S., Liepman, M. R., Nirenberg, T. D., & Young, C. M. (1991). Young adults knowledge of the strength of different alcoholic beverages. Journal of Drug Education, 21, Matthews, D. B., & Miller, W. R. (1979). Estimating blood alcohol concentration: Two computer programs and their applications in therapy and research. Addictive Behaviors, 4, National Institute on Alcohol Abuse and Alcoholism. (2000). Tenth special report to the U.S. Congress on alcohol and health (NIH Publication No ). Washington, DC: National Institutes of Health. National Institute of Alcohol Abuse and Alcoholism, Task Force of the National Advisory Council on Alcohol Abuse and Alcoholism. (2002). A call to action: Changing the culture of drinking at U.S. colleges (NIH Publication No ). Washington, DC: NIH. O Malley, P. M., & Johnston, L. D. (2002). Epidemiology of alcohol and other drug use among American college students. Journal of Studies on Alcohol, 14 (Suppl), U.S. Department of Health and Human Services. (2007). The surgeon general s call to action to prevent and reduce underage drinking. Washington, DC: U.S. Department of Health and Human Services, Office of the Surgeon General. Wechsler, H. (1996). Alcohol and American college campus: A report from the Harvard school of public health. Change, 28, Wechsler, H., Lee, J. E., Nelson, T. F., & Kuo, M. (2002). Underage college students drinking behavior, access to alcohol, and the influence of deterrence policies. Journal of American College Health, 50, Wei, J., Barnett, N. P., & Clark, M. Alcohol consumption and attendance at alcohol-free and alcohol-service parties among college students. Manuscript submitted for publication. White, A. M., Kraus, C. L., McCracken, L. A., & Swartzwelder, H. S. (2003). Do college students drink more than they think? Use of a free-pour paradigm to determine how college students define standard drinks. Alcoholism: Clinical and Experimental Research, 27, Received March 14, 2008 Revision received July 11, 2008 Accepted July 19, 2008