Effects of Mixing Energy Drinks With Alcohol on Driving-Related Skills

Abstract

Background: Energy drinks (EDs) reduce sleepiness and fatigue and improve driving performance whereas alcohol does just the opposite. Although it is a trendy combination among young people, the effects of alcohol mixed with EDs on driving performance have been poorly studied. The aim was to assess if there is an interaction between the effects of both drinks on driving-related skills as well as perceptions about driving ability.

Methods: We conducted a randomized, double-blind, and placebo-controlled 4-way crossover clinical trial. Participants were 16 healthy volunteers. Interventions of 60 g of ethanol and 750 mL of Red Bull (RB) were administered in 2 separated doses. Conditions were alcohol + RB placebo, alcohol + RB, alcohol placebo + RB, and both placebos. Objective performance was assessed using a tracking test and simple reaction time, N-Back, and movement estimation tasks. Additionally, willingness to drive, other subjective effects, and ethanol and caffeine blood concentrations were also measured.

Results: Alcohol increased the time outside the road in the tracking test and increased simple reaction time, but the addition of RB had no main or interaction effects on performance. Nonetheless, driving-related skills after alcohol + RB were better than after alcohol alone. Willingness to drive increased with the combination of drinks. RB also reduced alcohol-induced sedation whereas drunkenness did not change. These effects were seen even though alcohol + RB increased alcohol (14.8%) and caffeine plasma concentrations (17.6%).

Conclusions: Mixing EDs with alcohol predisposes consumers to drive under alcohol influence, perhaps in part because EDs counteract its detrimental effects on driving-related skills. Clinicaltrials.gov: NCT02771587.

Keywords: Alcohol; addiction; caffeine; driving-related skills; energy drinks; interaction; pharmacokinetics.

Figure 1.

Time course of effects for driving-related skills (differences to baseline). Data points and error bars represent mean and SD values for 16 participants. Conditions: alcohol (60 g); alcohol (60 g) + RB (240 mg caffeine); RB (240 mg caffeine); placebo. * P < .05 and ** P < .01 indicate alcohol significant differences with A/RB. Filled symbols indicate a significant difference from placebo (P < .05). The significance is only reported for the comparison of more interest (A vs A/RB) and also between all conditions and placebo. Other comparisons are not included in the figure to make it easy to understand.

Figure 2.

Time course of subjective effects (differences to baseline). Data points and error bars represent mean and SD values for 16 participants. Conditions: alcohol (60 g); alcohol (60 g) + RB (240 mg caffeine), RB (240 mg caffeine), placebo. *P < .05 and **P < .01 indicate alcohol significant differences with alcohol + RB. Filled symbols indicate a significant difference from placebo (P < .05). The significance is only reported for the comparison of more interest (A vs A/RB) and between all conditions and placebo. Other comparisons are not included in the figure to make it easy to understand.

Figure 3.

Time course of plasma concentrations of alcohol and caffeine. Data points and error bars represent mean and SD values for 16 participants. Amount of alcohol of 10 μmol/mL corresponds to 46.07 mg/dL and 20 μmol/mL to 92.1 mg/dL. Conditions: alcohol (60 g); alcohol (60 g) + RB (240 mg caffeine), RB (240 mg caffeine), placebo. *P < .05 and **P < .01 indicate significant differences among both conditions.