Factors Associated with Self-Estimated Breath Alcohol Concentration Among Bar Patrons

Few studies have examined the context in which drinkers underestimate their breath alcohol concentration (BrAC) in natural drinking environments. This study examined factors associated with bar patrons' self-estimated BrAC in high-risk college town settings.

Guided interview and BrAC data were collected from 510 participants recruited as they exited bars located close to large universities: 1 in Florida and 1 in Texas.

Participants with the highest measured BrACs underestimated their BrAC levels the most. Findings from multivariable linear regression analysis indicated that BrAC (std β = 0.014, p < 0.001), number of alcoholic drinks consumed (std β = 0.006, p < 0.01), and perceived drunkenness (std β = 0.024, p < 0.001) had significant positive associations with BrAC self-estimates, where the regression coefficients were scaled by values approximately equal to each variable's interquartile range. Among the 321 participants with BrAC levels ≥ 0.08 g/dl, 21.2% believed their BrAC was below the legal per se driving limit of 0.08 g/dl. Results from a logistic regression analysis indicated that higher levels of perceived drunkenness were associated with better self-recognition that one's BrAC level exceeded the legal driving threshold (OR = 3.312, p < 0.001). Further, participants under 26 years of age had reduced odds of recognizing that their BrAC was greater than 0.079 g/dl (OR = 0.245, p < 0.05).

These findings highlight the inaccuracy of self-estimated BrAC when drinking, particularly among younger drinkers. Adjusting for BrAC, situational factors were strongly associated with self-estimated BrAC. Future research is needed to better understand how altering drinking environments may improve accuracy of BrAC self-estimates and deter driving after drinking.