Post on 17-Jan-2016
Field Assessment of BAC Data to Study College
Drinking
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Dennis L. Thombs, Ph.D.
R. Scott Olds, H.S.D.
Kent State University
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Citations:Citations:
Thombs DL, Olds RS, & Snyder BM Thombs DL, Olds RS, & Snyder BM (2003). (2003). Field Assessment of BAC Data Field Assessment of BAC Data to Study to Study Late-Night College Drinking. Late-Night College Drinking. Journal of Journal of Studies on Studies on Alcohol, Alcohol, 64(3):322-33064(3):322-330
Olds RS & Thombs DL (2003). Blood Olds RS & Thombs DL (2003). Blood Alcohol Concentrations of College Alcohol Concentrations of College Women and Men Returning Home at Women and Men Returning Home at Night. Night. Alcohol Research, Alcohol Research, 8(6):271-8(6):271- 275275
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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
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Research Questions To what extent does the 5+/4+ measure To what extent does the 5+/4+ measure
detect higher levels of intoxication?detect higher levels of intoxication?
Do sex differences exist in late-night Do sex differences exist in late-night college drinking?college drinking?
To what extent does estimated BAC To what extent does estimated BAC predict actual BAC in a field setting?predict actual BAC in a field setting?
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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
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Late-Night Breath Sampling Protocol
Students were briefly interviewed Students were screened so data collected
from: a) residents;b) no more drinking that night; andc) no consumption in past 15
minutes Students were told prior to breath test
that they would not be given BAC feedback
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Recruitment 1,976 intercepts made during the
Spring Semester, 2002
641 (32.4%) immediately declined Most common reasons: a) foul
weather, b) “in a hurry,” c) with a date, d) “I have done it before”
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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
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Sample Profile 56% were men & 91% fresh./sophomores56% 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
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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
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Evaluation of the 5+/4+ “Binge Drinking”
Measure 44.6% of intercepted students reported 44.6% of intercepted students reported
consuming 4 or 5 drinks that nightconsuming 4 or 5 drinks that night Mean BAC of women “binge drinkers” Mean BAC of women “binge drinkers”
= .086 (g/dl)= .086 (g/dl) Mean BAC of men “binge drinkers” = .084 Mean BAC of men “binge drinkers” = .084
(g/dl)(g/dl)
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Evaluation of the 5+/4+ “Binge Drinking”
Measure Only 52% of the “binge drinkers” (both Only 52% of the “binge drinkers” (both
sexes) had BACs sexes) had BACs >> .08 (g/dl) .08 (g/dl) Only 34% of the “binge drinkers” (both Only 34% of the “binge drinkers” (both
sexes) had BACs sexes) had BACs >> .10 (g/dl) .10 (g/dl) Only 6% of the “binge drinkers” (both Only 6% of the “binge drinkers” (both
sexes) had BACs sexes) had BACs >> .15 (g/dl) .15 (g/dl)
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Sex Differences Although number of drinks (self-Although number of drinks (self-
report) distinguished between women report) distinguished between women (mean = 2.7) and men (5.3), there (mean = 2.7) and men (5.3), there was little difference in observed BAC was little difference in observed BAC (women = .04 vs. men = .05) (women = .04 vs. men = .05)
This suggests that college women This suggests that college women and men tend to self-titrate to similar and men tend to self-titrate to similar levels of intoxicationlevels of intoxication
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Figure 1. Figure 1. Medians, Interquartiles, and Ranges of Medians, Interquartiles, and Ranges of Estimated BAC Within Actual BAC Groups (n = 567). Estimated BAC Within Actual BAC Groups (n = 567).
Actual BAC mg/dl
150+140130120110100908070605040302010
Estim
ate
d B
AC
mg
/dl
200190180170160150140130120110100908070605040302010
0
Note that students with BACs equal to 0 mg/dl were excluded from 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 the figure. The number of students in the actual BAC groups ranged from 21 to 56.from 21 to 56.
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BAC Estimation in the Field
Students with BACs < .07 (g/dl) tended to overestimate their intoxication level
Students with BAC from .070-.099 (g/dl) tended to accurately estimate their intoxication level
Students with BAC > .10 (g/dl) tended to underestimate their intoxication level
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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
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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
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ConclusionsConclusions The 5+/4+ measure classifies many college The 5+/4+ measure classifies many college
students as “binge drinkers” even though their students as “binge drinkers” even though their BACs are below conventional levels used to BACs are below conventional levels used to define drunkenness define drunkenness
Underestimation of one’s intoxication is most Underestimation of one’s intoxication is most likely to occur at elevated BACslikely to occur at elevated BACs
Although college men tend to consume a greater Although college men tend to consume a greater quantity of alcohol, college women appear to quantity of alcohol, college women appear to drink to the same levels of intoxication as men drink to the same levels of intoxication as men