The acute effects of caffeinated versus non-caffeinated alcoholic beverage on driving performance and attention/reaction time.

AIMS: Marketing that promotes mixing caffeinated 'energy' drinks with alcoholic beverages (e.g. Red Bull with vodka) targets young drinkers and conveys the expectation that caffeine will offset the sedating effects of alcohol and enhance alertness. Such beliefs could result in unwarranted risk taking (e.g. driving while intoxicated). The aim of this study was to assess the acute effects of caffeinated versus non-caffeinated alcoholic beverages on a simulated driving task and attention/reaction time.

DESIGN: We conducted a 2 × 2 between-groups randomized trial in which participants were randomized to one of four conditions: beer and non-alcoholic beer, with and without caffeine added. Caffeine was added in the same proportion as found in a commercially available caffeinated beer (69 mg/12 oz of beer at 4.8% alc. by vol).

PARTICIPANTS: Participants were 127 non-dependent, heavy episodic, young adult drinkers (age 21-30) who were college students or recent graduates. The target breath alcohol level was 0.12 g%.

MEASURES: Driving performance was assessed with a driving simulator; sustained attention/reaction with the Psychomotor Vigilance Task (PVT).

FINDINGS: Across the driving and attention/reaction time we found main effects for alcohol, with alcohol significantly impairing driving and sustained attention/reaction time, with mainly large statistical effects; however, the addition of caffeine had no main or interaction effects on performance.

CONCLUSION: The addition of caffeine to alcohol does not appear to enhance driving or sustained attention/reaction time performance relative to alcohol alone.