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