The hazardous (mis)perception of Self-estimated Alcohol intoxication and Fitness to drivE—an avoidable health risk: the SAFE randomised trial

Köchling, Jöran; Geis, Berit; Chao, Cho‐Ming; Dieks, Jana-K.; Wirth, Stéfan; Hensel, Kai O. · 2021 · OpenAlex-citations

DOI: 10.1186/s12954-021-00567-4

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Summary

This study addresses the critical public health issue of alcohol-related road traffic accidents, focusing on the accuracy with which social drinkers can self-estimate their blood alcohol concentration (BrAC) relative to legal driving limits. The research was motivated by the widespread inability of individuals to correctly judge their fitness to drive after consuming alcohol, a factor that significantly contributes to avoidable morbidity and mortality. The primary objective was to evaluate the precision of self-estimated intoxication levels and to identify specific risk factors associated with misjudgment. The researchers conducted a prospective, randomized controlled crossover trial involving 90 social drinkers (mean age 23.9 years, 50% female). Participants were matched by age, sex, BMI, and drinking behavior, then randomized into study and control groups. Over two separate intervention days, subjects consumed either beer or wine until reaching a maximum BrAC of 0.11%. The study group was informed when they reached the legal driving limit (BrAC = 0.05%), while the control group received no such information. Breath alcohol concentrations were monitored repeatedly using breathalyzers, and participants were asked to report when they subjectively believed they had reached the legal limit. Statistical analyses, including paired t-tests and repeated measures ANCOVA, were used to assess estimation accuracy and identify predictors of inaccuracy. The results revealed significant inaccuracies in self-estimation. Between 39% and 53% of participants exceeded the legal driving limit while believing they were still permitted to drive. Specifically, on study day 1, 39% of those who thought they had reached the limit had actually exceeded it; this proportion rose to 53% on study day 2. Self-estimation accuracy improved significantly on the second study day (p = 0.009), suggesting a learning effect. A strong positive correlation was observed between increasing BrAC levels and the degree of underestimation, meaning participants became increasingly unaware of their intoxication as their alcohol levels rose. Multiple regression analysis identified fast drinking rates and higher peak alcohol levels as independent risk factors for inaccurate self-estimation. Conversely, the type of beverage (beer vs. wine) did not significantly impact estimation accuracy. The study concludes that social drinkers are frequently unaware when they exceed legal driving limits, posing a substantial safety hazard. The findings indicate that self-estimation of intoxication is a learnable skill, as awareness of the issue improved accuracy in subsequent trials. The authors recommend implementing dedicated awareness programs, social media campaigns, and government communications to mitigate this risk. Additionally, the study highlights a positive correlation between national legal driving limits and alcohol-related traffic deaths across various countries, underscoring the global relevance of improving public understanding of alcohol impairment.

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• public messaging

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• Applied Guidance: countermeasure evaluation