Inconsistencies between actual and estimated blood alcohol concentrations in a field study of college students: do students really know how much they drink?
BACKGROUND
Alcohol use by college students is commonly measured through the use of surveys. The validity of such data hinge on the assumption that students are aware of how much alcohol they actually consume. Recent studies call this assumption into question. Students tend to overestimate the appropriate sizes of standard drinks, suggesting that they might underestimate how much alcohol they consume. If this is true, then students' actual blood alcohol concentrations (BACs) should be higher than BACs estimated based on self-report data. The present study examined this issue


METHODS
Breathalyzer readings and self-reported drinking data were collected from 152 college students during the fall of 2004. Estimated BACs were calculated by means of a standard formula, and the relation between actual and estimated BACs was examined. Factors contributing to discrepancies between the two values were identified


RESULTS
Estimated BAC levels were significantly higher, not lower, than breath BAC measures. The accuracy of estimated BACs decreased as the number of drinks and amount of time spent drinking increased. Being male and drinking only beer predicted greater accuracy of estimated BACs


CONCLUSIONS
Although laboratory data suggest that students underestimate how much they drink, the hypothesis was not supported by data collected in the field. It appears that students might actually overestimate rather than underestimate their levels of consumption when surveyed in the midst of a night of drinking. The findings corroborate observations made by other researchers and suggest that the findings of laboratory studies on college drinking do not necessarily extend to real-world settings.
Kraus
Courtney L
CL
Department of Psychiatry, Duke University Medical Center, Durham, NC 27710, USA.
Salazar
Natasha C
NC
Mitchell
Jamie R
JR
Florin
Whitney D
WD
Guenther
Bob
B
Brady
David
D
Swartzwelder
Scott H
SH
White
Aaron M
AM
D000328:Adult; D000428:Alcohol Drinking / Q000097:blood* / Q000523:psychology; D000431:Ethanol / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D012044:Regression Analysis; D012737:Sex Factors; D013334:Students; D014495:Universities
D000431:Ethanol