Field Assessment of BAC Data to Study College Drinking

2 Dennis L. Thombs, Ph.D. R. Scott Olds, H.S.D. Kent State University

3 Citations: Thombs DL, Olds RS, & Snyder BM (2003). Field Assessment of BAC Data to Study Late-Night College Drinking. Journal of Studies on Alcohol, 64(3): Olds RS & Thombs DL (2003). Blood Alcohol Concentrations of College Women and Men Returning Home at Night. Alcohol Research, 8(6):

4 Rationale The study of college drinking has rarely relied on objective measures of intoxication. Self-report measures of alcohol use, particularly those assessing quantity of consumption, are frequently viewed with skepticism

5 Research Questions To what extent does the 5+/4+ measure detect higher levels of intoxication? To what extent does the 5+/4+ measure detect higher levels of intoxication? Do sex differences exist in late-night college drinking? Do sex differences exist in late-night college drinking? To what extent does estimated BAC predict actual BAC in a field setting? To what extent does estimated BAC predict actual BAC in a field setting?

6 Late-Night Breath Sampling Protocol KSU students intercepted as they returned to residence halls – 10:00 p.m. to 3:00 a.m. Wednesday through Saturday nights for 15 weeks of Spring Semester, 2002 Area sampling procedure used to intercept a representative sample of residence hall students

7 Late-Night Breath Sampling Protocol Students were briefly interviewed Students were screened so data collected from: a) residents; b) no more drinking that night; and c) no consumption in past 15 minutes Students were told prior to breath test that they would not be given BAC feedback

8 Recruitment 1,976 intercepts made during the Spring Semester, (32.4%) immediately declined Most common reasons: a) foul weather, b) “in a hurry,” c) with a date, d) “I have done it before”

9 Screening Results Among 1,335 participants, 265 (19.8%) were screened out of data collection Most of these individuals indicated they were not KSU students A total of 1,020 students were screened and provided complete data

10 Sample Profile 56% were men & 91% fresh./sophomores 56% were men & 91% fresh./sophomores Most common drinking site was the dorms Most common drinking site was the dorms Time to last drink: mean = 38 min.(sd=60) Time to last drink: mean = 38 min.(sd=60) Correlation between BAC and number of minutes since last drink was weak (r = -.15, n = 1,020, p <.001) - suggesting observed intoxication levels approximated peak BACs for the night Number of intercepts (sample mean = 4.4, sd = 7.6) was not related to BAC

11 BAC by Night of Week Wednesdays: Mean =.02 (5% >.10 g/dl) n = 227 Thursdays: Mean =.05 (19% >.10 g/dl) n = 380 Fridays: Mean =.05 (16% >.10 g/dl) n = 229 Saturdays: Mean =.06 (21% >.10 g/dl) n = 184

12 Evaluation of the 5+/4+ “Binge Drinking” Measure 44.6% of intercepted students reported consuming 4 or 5 drinks that night 44.6% of intercepted students reported consuming 4 or 5 drinks that night Mean BAC of women “binge drinkers” =.086 (g/dl) Mean BAC of women “binge drinkers” =.086 (g/dl) Mean BAC of men “binge drinkers” =.084 (g/dl) Mean BAC of men “binge drinkers” =.084 (g/dl)

13 Evaluation of the 5+/4+ “Binge Drinking” Measure Only 52% of the “binge drinkers” (both sexes) had BACs >.08 (g/dl) Only 52% of the “binge drinkers” (both sexes) had BACs >.08 (g/dl) Only 34% of the “binge drinkers” (both sexes) had BACs >.10 (g/dl) Only 34% of the “binge drinkers” (both sexes) had BACs >.10 (g/dl) Only 6% of the “binge drinkers” (both sexes) had BACs >.15 (g/dl) Only 6% of the “binge drinkers” (both sexes) had BACs >.15 (g/dl)

14 Sex Differences Although number of drinks (self-report) distinguished between women (mean = 2.7) and men (5.3), there was little difference in observed BAC (women =.04 vs. men =.05) Although number of drinks (self-report) distinguished between women (mean = 2.7) and men (5.3), there was little difference in observed BAC (women =.04 vs. men =.05) This suggests that college women and men tend to self-titrate to similar levels of intoxication This suggests that college women and men tend to self-titrate to similar levels of intoxication

15 Figure 1. Medians, Interquartiles, and Ranges of Estimated BAC Within Actual BAC Groups (n = 567). Note that students with BACs equal to 0 mg/dl were excluded from the figure. The number of students in the actual BAC groups ranged from 21 to 56.

16 BAC Estimation in the Field Students with BACs <.07 (g/dl) tended to overestimate their intoxication level Students with BAC from (g/dl) tended to accurately estimate their intoxication level Students with BAC >.10 (g/dl) tended to underestimate their intoxication level

17 BAC Estimation in the Field Estimated BAC accounted for only 20% of the variance in actual BAC Among the 159 students with BACs >.10 (g/dl), only 55% estimated their BAC to equal or exceed same level

18 Conclusions Findings from this field assessment suggest that some of the concerns about self-report survey methods are warranted Investigators studying college drinking should incorporate night-night BAC data into assessment batteries

19 Conclusions The 5+/4+ measure classifies many college students as “binge drinkers” even though their BACs are below conventional levels used to define drunkenness The 5+/4+ measure classifies many college students as “binge drinkers” even though their BACs are below conventional levels used to define drunkenness Underestimation of one’s intoxication is most likely to occur at elevated BACs Underestimation of one’s intoxication is most likely to occur at elevated BACs Although college men tend to consume a greater quantity of alcohol, college women appear to drink to the same levels of intoxication as men Although college men tend to consume a greater quantity of alcohol, college women appear to drink to the same levels of intoxication as men