Abstract
Introduction and Aims
In December 1999, New Zealand lowered the alcohol minimum purchasing age from 20 to 18 years. We tested hypotheses that this change was associated with long‐term increases in traffic injury attributable to alcohol‐impaired driving among 18‐ to 19‐year‐olds (target age group) and 15‐ to 17‐year‐olds (affected by ‘trickle‐down’).
Design and Methods
We undertook a controlled before‐and‐after comparison of rates of fatal and non‐fatal traffic injury to persons of any age attributable to impaired drivers aged 18–19 years and 15–17 years, versus 20‐ to 21‐year‐olds. Crash data including assessment of driver alcohol impairment were recorded by New Zealand Police. The pre‐change period was 1996–1999. Post‐change periods were 2000–2003, 2004–2007 and 2008–2010. Outcomes were population‐based and vehicle travel‐based rates.
Results
Compared with the change in injury rates attributable to alcohol‐impaired 20‐ to 21‐year‐old male drivers, injuries attributable to 18‐ to 19‐year‐old male drivers increased in all post‐change periods and significantly so in the second post‐change period (incidence rate ratio [IRR] 1.3, 95% confidence interval [CI] 1.1 to 1.5). For 15‐ to 17‐year‐old male drivers, rates increased in all post‐change periods compared with 20‐ to 21‐year‐olds, and more so in the second (IRR 1.2, 95% CI 1.1 to 1.4) and third (IRR 1.2, 95% CI 1.1 to 1.4) periods. There was a short‐term relative increase in harm attributable to 18‐ to 19‐year‐old female drivers (IRR 1.5; 1.1 to 2.0). Results were similar for vehicle travel‐based rates.
Discussion and Conclusions
Reducing the alcohol minimum purchasing age was followed by long‐term increases in the incidence of traffic injury attributable to male 15‐ to 19‐year‐old alcohol‐impaired drivers. [Kypri K, Davie G, McElduff P, Langley J, Connor J. Long‐term effects of lowering the alcohol minimum purchasing age on traffic crash injury rates in New Zealand. Drug Alcohol Rev 2017;36:178–185]