People with chronic health conditions cost the accident compensation system 59 per cent more than healthy people without those conditions, researchers have found.
Although only a minority of people suffer from any of the conditions, their non-accident-related conditions account for 10.7 per cent of total accident compensation costs, or $276 million a year.
The findings, obtained by Accident Compensation Corporation clients Bruce Van Essen and Bronwyn Pullar under the Official Information Act, raise fears that ACC may try to avoid paying for costs that are arguably due to chronic health conditions.
"I can't understand why you would go to all that trouble to collect data and not use it," said Ms Pullar, who blew the whistle on ACC's poor privacy processes after she was sent almost 7000 ACC files about other people by accident in 2012.
A Wellington legal specialist on ACC cases, John Miller, said ACC was already increasingly refusing to accept compensation claims by pointing to "degeneration" that existed before an accident, often due to aging.
"It's going to continue and probably get worse and ACC is looking at shifting some of those costs on to the health sector," he said.
The findings come from a series of reports dating back to 2009.
The first 2009 report by CBG Health Research, headed by Internet Party leader Laila Harre's husband Dr Barry Gribben, found that people with any of six chronic health conditions had nearly twice as many ACC-funded health consultations as people without any of those conditions.
A 2010 internal ACC report found that diabetes and coronary heart disease alone increased ACC costs by $100 million a year.
A final 2012 report, again by CBG Health Research, calculated the costs of nine common health conditions which between them affect 40 per cent of New Zealanders.
It found increased ACC costs ranging from 3 per cent for people with asthma to 84 per cent for people with mental health conditions, with an average excess across all nine conditions of 59 per cent.
All the studies found that the increased costs were due to people with chronic health conditions both having more accidents and taking longer to recover from them and get back to work.
The reasons were often complicated. For example, people with chronic health conditions were more likely to become unemployed, which increased their chances of developing mental health and/or alcohol and drug problems, which in turn affected their accident and recovery rates.
Most of the health conditions also became more common with age. CBG calculated that our aging population would increase the share of ACC costs due to chronic health conditions from 10.7 per cent to 12.7 per cent by 2025.
An ACC spokeswoman said better understanding of the effects of chronic health conditions would "allow for better rehabilitation outcomes for clients" as well as possible "policy measures to address the additional cost burden to ACC".
Mr Miller said the research showed the need for a "holistic" approach to address people's chronic conditions at the same time as their accident-related injuries. He said ACC was best-placed to coordinate such an approach because it assigned everyone a personal case manager.
What it costs
How much common health conditions increase ACC costs
Mental illness +84%
Coronary heart disease +57%
Heart failure +42%
High blood pressure +41%
Average: any of the above +59%