Background: Previous research on alcohol mixed with energy drinks (AmED) suffers from measurement problems. Missing from the research literature are studies that assess caffeine-alcohol co-ingestion in natural drinking environments. Methods: This field study collected data in a U.S. college bar district from 328 randomly selected patrons. Anonymous data were obtained from face-to-face interviews and self-administered surveys, and from breath tests. Results: Cola-caffeinated alcoholic beverage consumers left bars in a more highly intoxicated state than those who consumed alcohol only. There was no significant difference between the intoxication level of the AmED group and the cola-caffeinated alcoholic beverage group. Results from a multivariate regression model indicated that quantity of caffeinated alcoholic beverage consumption had a significant, positive association with bar patron intoxication after adjusting for potential confounders. Conclusions: Findings indicate that caffeine may have a dose-dependent relationship with alcohol intoxication in the bar/nightclub setting. In addition, results revealed that cola-caffeinated alcoholic drinks may pose similar levels of risk to bar patrons as those associated with AmED beverage consumption. Product labeling requirements about alcohol risks may need to be extended not only to energy drinks, but to caffeinated soft drinks as well.
- Breath alcohol concentration
- Energy drinks