Bourbon is likely to cause worse hangovers than vodka, though both are equally likely to impair cognitive functions in the morning, according to a new study by Professor of Community Health Damaris Rohsenow.
The study, to be published in the March issue of Alcoholism: Clinical and Experimental Research, points to the amounts of "congeners," toxic organic compounds used in fermentation and found in bourbon, as significant to the degree of hangover. Though congeners only appear in very small quantities in alcoholic beverages, bourbon contains 37 times the amount of congeners as vodka, according to the study.
According to a press release from the journal, the researchers recruited 95 heavy drinkers aged 21 to 33 who did not have any history of alcohol abuse and paid them to sleep several nights at their labs at Boston University. The participants would drink the minimum amount of bourbon or vodka needed to induce a hangover on one night, and consume a placebo another night.
Rohsenow said the researchers studied the sleep patterns of the participants and asked them to fill out an acute hangover scale — rating the severity of their hangovers — once their blood alcohol levels had returned to normal. The researchers then asked the participants to take several cognitive tests requiring vigilant attention and quick, accurate decision-making, Rohsenow said.
According to Rohsenow, participants ranked the bourbon hangovers as worse, but performance in cognitive tests was equally hindered regardless of beverage.
Rohsenow also said many participants did not realize that their cognitive performance was diminished.
"People were not aware that their performance was impaired the next morning," Rohsenow said, adding that this held true even for the 25 to 30 percent of heavy drinkers who claim to not experience hangovers.
"Many times, people cannot judge their own ability to be safe," Rohsenow said.
