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Lowering the drinking age has resulted in more young men being hospitalised with assault injuries, University of Otago research has found.
Lead researcher Kypros Kypri said the research was more evidence that Parliament failed New Zealanders when it bungled a vote in 2012 on raising the alcohol purchasing age.
He believed raising the drinking age should be looked at again and any movement would have a greater impact on Dunedin than elsewhere, because of the proportion of young people in the city.
''You would expect that anything that affects alcohol consumption among young people will be especially effective in Dunedin because of that.''
The study, published in theAmerican Journal of Public Health, looked at patients admitted to New Zealand hospitals with assault injuries on weekends four years before, and up to 12 years after, the alcohol purchasing age was reduced to 18 in 1999.
It found the rate of increase for hospital admissions due to assaults was a fifth higher for 18- and 19-year-old men and a quarter higher for 15- to 17-year-old males than 20- and 21-year-old men, who were unaffected by the change.
Previous studies had shown reducing the purchasing age had resulted in increased traffic injuries, but no other study had looked at assaults.
''There had been no such studies of the effects on assault which is an increasingly important problem in New Zealand and other countries that have liberalised access to alcohol among young people.''
While there were straightforward ways to reduce alcohol-related traffic injuries - such as changing blood-alcohol rules - evidence suggested it was more difficult to reduce the number of alcohol-related assaults.
Restricting the availability and promotion of alcohol were two key ways to reduce the numbers of alcohol-related assaults.
Among females, the differences between the three age groups over time were not statistically significant. Report co-author Jennie Connor said there was ''insufficient statistical power to properly examine the effect of the law change on females''.
''This is partly because the assault rate is so much lower among females than males, but it is also likely that the dynamics of assault are quite different when females are injured.
''While girls and young women are drinking more than ever, they still account for only one in five or six assault hospitalisations.
''Assault remains predominantly a problem affecting young men and is likely to be contributing to the gender gap in health.''