Heavy drinking impairs balance and motor coordination, which is why increased body sway is a useful indicator to both police and bartenders that a person may be intoxicated. People often drink alcohol at the same time that they ingest stimulant drugs such as caffeine or nicotine, yet it is unclear how these stimulants affect alcohol-induced balance impairment. This study examined whether combining a high-caffeine energy drink with alcohol can influence expected alcohol-induced increases in body sway.
Sixteen social drinkers (8 women, 8 men) between the ages of 21 and 30 years participated in four "blinded" sessions during which they drank alcohol, soft drinks, and energy drinks alone or in combination. Following alcohol consumption, participants were assessed for balance stability (both with their eyes open and closed), and reported their ratings of sedation, stimulation, fatigue and impairment. Blood pressure and pulse rate were also recorded.
Energy drinks appeared to influence alcohol-induced body sway. Specifically, when participants had their eyes open, their alcohol-induced increases in body sway were smaller if energy drinks had been consumed as well. Conversely, when participants had their eyes closed, alcohol-induced body sway was not influenced by energy-drink consumption, indicating that visual feedback plays an important role in the influence of energy drinks on alcohol-induced motor impairment. The authors recommended further research to determine whether the same findings apply when alcohol is consumed in combination with other types of stimulant drugs.