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College students may be unable to accurately estimate whether they are above legal limit to drive after drinking

Adults aged 21 to 24 years are at elevated risk of driving after drinking in the U.S.; tolerance and external factors (e.g., number of drinks consumed) may make it difficult for individuals to accurately assess their own levels of intoxication. A new field research study compared self-estimates and objective measures of breath alcohol concentration (BrAC) levels among 510 bar patrons near universities in Florida and Texas. Participants were asked to estimate their BrAC levels using a graphic scale, report the number of drinks consumed, perceived intoxication levels, and other data. After recording this information, research assistants measured participants’ BrAC levels and provided feedback on their current levels of intoxication. Results showed only 38.6% of participants accurately estimated their BrAC levels within 0.02g/dl and 23.5% underestimated their BrAC levels by more than 0.04 g/dl. Nearly one-fifth of the 62.9% of participants who had BrAC levels at or above 0.08g/dl believed they were below the legal driving limit. After statistical analyses, the authors concluded participants with measured BrAC levels over 0.10 g/dl tended to underestimate their BrAC levels, especially those with measured BrAC levels of 0.20 g/dl or higher. Reported number of drinks consumed and perceived drunkenness were positively associated with BrAC self-estimates.

Take away: This study offers further evidence that intoxicated individuals are unable to accurately estimate their breath alcohol concentration (BrAC) levels. Individuals in this sample with measured BrAC levels above the legal limit to drive tended to underestimate their levels of intoxication.

Citation: Rossheim ME, Barry AE, Thombs DL, et al. (2017). Factors associated with self-estimated breath alcohol concentration among bar patrons [published online ahead of print July 6 2017], Alcoholism: Clinical and Experimental Research doi: 10.1111/acer.13428

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