The effect of lowering the legal blood alcohol concentration limit on driving under the influence (DUI) in southern Taiwan: a cross-sectional retrospective analysis

OBJECTIVES: We aimed to profile the epidemiological changes of driving under the influence (DUI) in southern Taiwan after the legal blood alcohol concentration (BAC) limit was lowered from 50 to 30 mg/dL in 2013. SETTING: Level 1 trauma medical centre in southern Taiwan. PARTICIPANTS: Data from 7447 patients (4375 males and 3072 females) were retrieved from the trauma registry system of a single trauma centre to examine patient characteristics (gender, age and BAC), clinical outcome variables (Abbreviated Injury Score, Injury Severity Score and mortality) and vehicular crash-related factors (vehicle type, airbag use in car crashes, helmet use in motorcycle crashes and time of crash) before and after the BAC limit change. RESULTS: Our results indicated that the percentage of DUI patients significantly declined from 10.99% (n=373) to 6.64% (n=269) after the BAC limit was lowered. Airbag use in car crashes (OR: 0.30, 95% CI 0.10 to 0.88, p=0.007) and helmet use in motorcycle crashes (OR: 0.20, 95% CI 0.15 to 0.26, p<0.001) was lower in DUI patients compared with non-DUI patients after the BAC limit change, with significant negative correlation. DUI behaviour increased crash mortality risk before the BAC limit change (OR: 4.33, 95% CI 2.20 to 8.54), and even more so after (OR: 5.60, 95% CI 3.16 to 9.93). The difference in ORs for mortality before and after the change in the BAC legal limit was not significant (p=0.568). CONCLUSION: This study revealed that lowering the BAC limit to 30 mg/dL significantly reduced the number of DUI events, but failed to result in a significant reduction in mortality in these trauma patients.