Impacts of New Zealand's lowered minimum purchase age on context-specific drinking and related risks

AimsThe minimum purchase age (MPA) for alcohol in New Zealand (NZ) was reduced from 20 to 18 years in 1999. We assessed the degree to which this change was associated with alterations in uses of drinking contexts, drinking and related problems. MethodsNZ National Alcohol Surveys among people 14+ years of age provided demographics, frequencies and amounts consumed in drinking places, and problem measures for 1995, 2000 and 2004. Censored regression estimates of parameters of a context-specific dose-response model identified MPA-associated changes in drinking and problems. ResultsThe lowered MPA was associated with more frequent drinking at pubs/nightclubs among the newly of-age 18-19-year-olds (b=15.26, P=0.009), moderated drinking quantities at these places (b=-0.94, P=0.034) and greater quantities consumed at home (b=1.01, P=0.010) and others' homes (b=0.87; P=0.029). Drinking frequency and quantity in the 16-17-year age group increased at home (b=22.11, P=0.040 and b=1.22, P=0.002) and others' homes (b=11.65, P=0.002 and b=0.91, P=0.021). Problems associated with drinking contexts changed post-MPA (G(2)27.45, P0.002), specifically increased association with drinking in pubs/nightclubs (b=0.09, P<0.001) across both age groups. ConclusionsThe 1999 change in New Zealand's minimum purchase age for alcohol from 20 to 18 years appears to have been associated with substantive changes in uses of drinking contexts, drinking and associated drinking problems among 16-19-year-olds.