After repeated use of the mobile app, heavy drinkers reduced their blood-alcohol concentrations prior to testing
Researchers analyzed data from tens of thousands of people who used low-cost mobile breathalyzers to test their blood-alcohol concentration when drinking. The analysis revealed that the repeated use of these devices corresponded to changes in drinking behavior and improved accuracy of self-assessments of blood-alcohol levels.
The findings are reported in the American Journal of Psychiatry.
While the study doesn’t prove that the breathalyzers caused the changes in behavior or awareness, it does suggest that mobile health devices may help heavy drinkers, in particular, self-monitor and reduce the potential harms of excessive drinking, said Yang Lu, a Ph.D. student who led the study with University of Illinois Urbana-Champaign psychology professor Catharine Fairbairn, the principal investigator of the Alcohol Research Laboratory at the U. of I.
The study relied on data from more than 32,000 people who tested their own blood-alcohol concentration, or BAC, by using a popular mobile breathalyzer and associated software. These users had consented to have their anonymous data made available to scientists. Those selected for the new study had used the mobile breathalyzers at least three times between 2016 and 2022. On average, participants used the device 40 times over a period of seven months.
The breathalyzer instructions asked users to wait 15 minutes after taking their last drink of alcohol before blowing into the device. Prior to taking the test, they were invited to guess their blood-alcohol concentration. For the new study, those guesses were compared with readings from the device.
“Most people tend to underestimate their blood-alcohol levels,” Yang said. “When I speak with clients who struggle with alcohol use, they’re often surprised by their BAC results. They don’t realize how much they’re drinking compared to others, and their perception of intoxication becomes quite distorted over time.”
The introduction of mobile health devices like mobile breathalyzers allows people to monitor their own health status in real time, in this case tracking how their intoxication levels change as they engage in their typical drinking behaviors, Fairbairn said.
“We’re seeing a movement away from the clinic and into people’s smartphones for how they want to manage their behavior and their health,” she said. “This data allows scientists and health care professionals to figure out whether these mobile health tools are helping or hurting.” Having such a large dataset of people’s alcohol-related behaviors outside the laboratory provided an ideal opportunity to study their real-world decision making and perceptions.
The study found that nearly 70% of participants underestimated their blood-alcohol concentration when first using the breathalyzer.
“That’s particularly concerning, especially for the heavy drinkers, because they don’t realize that their true BACs are actually higher,” Lu said. “That may lead to more impaired decisions about driving, about risk-taking.”
With increasing use of the breathalyzer, participants were better able to predict their blood-alcohol levels. Their accuracy increased by 2.38% across the average duration of use in the study, the researchers found. This suggests that the use of the breathalyzer enhanced their awareness of their own level of intoxication, Fairbairn said. Such awareness is key to making better decisions around drinking, she said. Further research is needed to confirm and extend the results, she said.
The study also found important differences between the heavy drinkers, who tended to underestimate their blood-alcohol levels, and the light drinkers, who overestimated them. Both groups increased the accuracy of their self-assessments over time, and both altered their drinking behavior as they used the breathalyzer.
“Among heavy-drinking participants, BAC levels decreased on average from 0.106% to 0.096%, whereas the reverse trend was observed for lighter-drinking participants, whose levels increased from 0.058% to 0.067%,” the researchers wrote.
Because this was not a randomized-controlled trial where all variables would be accounted for and user experience standardized, the findings do not prove that having access to a private breathalyzer test caused the changes in behavior, Fairbairn said. But it does suggest that DIY approaches to monitoring blood-alcohol levels could be influencing their self-awareness and behavior.
“The prevailing wisdom is that monitoring your behavior will make your behavior better,” she said. “And we did find evidence to support that. We found that people increase their accuracy in estimating their BAC over time, and the most potentially vulnerable populations, heavy drinkers, did decrease their drinking over time. But we also found nuance in this, in that the light drinkers actually slightly edged upward.”
The findings suggest that people are relying on familiar concepts such as a blood-alcohol concentration of 0.08% as the legal driving limit and may aim to be under that limit but not far off, the researchers said. However, that notion remains to be tested.
“These initial findings are very promising for the potential harm-reduction utility of mobile breathalyzers and other objective-feedback tools,” Lu said. “We are continuing to explore how people use and learn from such devices.”
