This is the first known investigation to assess event-level
associations between energy drink consumption and alcohol-related
risk behaviors in a natural drinking environment. We hypothesized
that consuming energy drinks mixed with alcohol would be
associated with significant increases in the odds of: (1) exiting a bar
in a highly intoxicated state and (2) intending to drive upon leaving a
bar. In support of the first study hypothesis, multivariable analysis
found that exiting bar patrons who reported consuming energy drinks
mixed with alcohol were 3.32 times more likely to have a
BrAC≥0.080 g/210 L, after adjusting for demographic characteristics,
alcohol dependence risk, and consumption of energy drinks and
alcohol at different times in the same night (not mixed together).
Furthermore, analyses indicated that patrons who consumed alcohol
mixed with energy drinks, on average, exited a bar later in the
evening, engaged in drinking for a longer period of time, consumed
more total drinks and more grams of ethanol, and had higher levels of
alcohol intoxication, compared to patrons who did not consume
energy drinks that night or who consumed energy drinks and alcohol
at different times in the same night (not mixed together).
In support of the second study hypothesis, results from multivariable
analysis revealed that bar patrons who reported consuming
energy drinks mixed with alcohol were 4.26 times more likely to
report an intention to drive a motor vehicle from the bar district.
These findings suggest that consuming energy drinks mixed with
alcohol may reduce perceptions of alcohol impairment, and thus,
increase one's confidence in operating a vehicle under the influence
of alcohol. One clinical study found that, compared to consumption
of an alcoholic beverage alone, consumption of an energy drink
mixed with alcohol did not reduce objective impairment of motor
coordination and visual reaction time, but did significantly reduce
subjective symptoms of alcohol intoxication such as headache,
weakness, dry mouth, and impaired motor coordination (Ferreira
et al., 2006). These results are consistent with other studies investigating
the combined ingestion of caffeine and alcohol (Liguori &
Robinson, 2001; Marczinski & Fillmore, 2006). Thus, consumers of
energy drinks mixed with alcohol may misinterpret their level of
inebriation and attempt to drive a car or perform other potentially
hazardous activities.
These findings corroborate previous studies using different
methods and suggest that at the event-level, combining the stimulant
effect of energy drinks with alcohol reduces the symptomatic lethargy
associated with drunkenness, which may lead drinkers to underestimate
their levels of intoxication and consume larger quantities
of alcohol (Finnegan, 2003; Reissig et al., 2009). However, a second
potential explanation for these findings may involve chronic heavy
drinking; that