Waikato Hospital Emergency Department head John Bonning said in order for alcohol-related admissions to decrease, bars need to close earlier.

A Waikato doctor is fed up with the number of drunks who turn up at his emergency department. They're not just diverting attention from truly sick people, they're assaulting his staff.

"We get vomited on, occasionally hit, frequently verbally abused - there's a lot of swearing," Waikato Hospital Emergency Department head John Bonning said.

"And it's just so frustrating when you have to divert care from the elderly, who are potentially more deserving, to deal with [drunk] people that really have preventable issues going on. There're a lot of very deserving sick elderly people that get into trouble with their medical problems.

"Obviously it's a part of our job, but we deal with a number of people that are really, really intoxicated."

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Bonning said a study into the effects of alcohol on emergency departments in Australia and New Zealand shows more than 90 per cent of staff reported being physically or verbally assaulted by drunk patients.

He said the holiday period saw one in eight patients present with alcohol-related injuries or illness.

"We're incredibly busy over the holiday period. Christmas Day is usually quiet, but then it absolutely blows out after that and for a variety of reasons.

"There are no alternatives - GPs are all closed and there are very few medical centres open."

Bonning said young people are over-represented among the drunks.

He once attended to a young, intoxicated man, who was detained at a police station.

"The guy actually said to me, 'I wish I hadn't drunk so much last night, I wouldn't be in the trouble that I'm in now.'

"And another snapshot story I have is, on a couple of consecutive Saturday nights, I found seven people under 20 years old in the emergency department because of alcohol."

Information obtained under the Official Information Act shows 174 people aged 15 to 17 were admitted to the Waikato Hospital emergency department over a five year period.

Alcohol was by far the most commonly used recreational drug between 2011 and 2015.

Fifteen youths were admitted to the department for codeine use, nine for cannabis, seven for mushrooms and one for ecstasy.

And in the same period, there were 35 children aged 10 to 14 who ended up in the ED for using alcohol.

The Australasian study concluded that 8.3 per cent of all presentations in any one 24-hour period is alcohol related, and this increased to 12 per cent from 6pm to 6am Friday, Saturday and Sunday. Seventeen per cent of those had suffered unintentional injury while intoxicated and 14 per cent had been injured due to someone else's intoxication (such as assaults and motor vehicle accidents).

Bonning said the key to fewer alcohol-related admissions is to have bars and pubs close earlier. He gave Sydney's popular nightlife spot Kings Cross as an example.

"They closed the bars earlier and it was completely dead after midnight, but people weren't fighting each other and stealing each other's possessions.

"Most people use alcohol responsibly. But it's those that get into fights, fall over or get behind the wheel of a car or assault other people that are really causing the major problems."

He said the recent studies have confirmed what health professionals have known all along.

"Every hour you close after midnight results in a 20 per cent reduction in serious assaults. That is a real figure.

"It shows that you really shouldn't have bars open after 4am. And the more you drink, the more likely you are to partake in these at-risk behaviours.

"So the community needs to understand the issue, they need to understand the problems of [bars and pubs] opening late."

Bonning said there are ongoing studies into the effects of alcohol on our health departments, the next to take place on Australia Day.

"Australians drink quite a lot on that day, and New Zealand will be set up as the control site, hoping that it's just a normal day in New Zealand," he said. "It should be interesting."

He said the bottom line for him is a "broken-record phrase".

"If you're going to drink alcohol, do so in moderation and make safe choices. Don't fall over, don't get into a fight and don't get behind the wheel of a car.

"When you think that the care of some people might need to suffer because of these [drunk] people, please, don't come into our emergency department with the effects of alcohol because there are other more deserving people that we need to work on."