Our high quality public health data means New Zealand can tackle a globally "surprising lack'' of costing studies on patients with multiple diseases, Prof Tony Blakely says.
A just-published University of Otago study led by Prof Blakely made the point that one plus one equals more than two for health spending in patients with multiple conditions.
The research showed that caring for patients with two or more chronic diseases cost the health system more than it would to treat each disease in isolation.
Prof Blakely, of the university's Wellington campus, is the first author of the study on the health costs generated by individual diseases in patients and the extra costs of treating patients with multiple noncommunicable diseases.
This study is one of the first to assess the cost of multimorbidity on the public health system, and was published in the journal PLOS Medicine.
The researchers said that internationally there was a "surprising lack'' of disease-attributed costing studies that examined multiple diseases in the same patients.
"Governments and health systems managers can improve planning and prioritisation, knowing where the money goes, '' the study said.
Cost effectiveness studies also "usually needed costs by disease to model cost offsets from preventing disease''.
Prof Blakely said that Otago researchers had already been having discussions with the Ministry of Health over issues raised in the study.
"We should be making the best use of our [public health] data,'' he added.
What stood out in the research was the "high cost of musculoskeletal and neurological diseases'' and this was "greater than the priority we give them in planning and health services research''.
Across all chronic diseases, health spending was "unsurprisingly highest'' in the year of diagnosis and the year of death.
Costs in the year of death, if dying from chronic kidney disease, musculoskeletal, or diabetes were "particularly prominent'', ranging from $13,000 to more than $30,000.
Researchers studied health data for all adult New Zealanders and found 59% of publicly-funded health spending was attributable to non-communicable or chronic diseases.
Almost a quarter (23.8%) of that was spent on caring for patients with two or more diseases was above and beyond what the diseases cost individually, Prof Blakely said.
"If there were no additional costs due to the complexity of having two or more diseases at the same time, we would spend a quarter less on chronic conditions.'' The study found that the extra "comorbidity cost'' arising from multiple diseases in the same patient was "far more prominent at younger ages'', and further research to understand this age variation was "warranted''.
The extra cost with younger patients could arise from young people with multiple diseases being "treated more aggressively'' than old people with the same conditions, or that young people with more than one disease would have more severe disease than than their young counterparts with only one disease.
The research offered an insight into the extra financial burden posed by patients suffering from multiple conditions and would be useful for health planners in future.
New Zealand's high quality public health data meant that our researchers could do analytical work "that many other countries can't,'' he added in an interview.
More research was needed and multimorbidity was "likely to be an increasing driver of health spending in future, as people live longer,'' he said.
The researchers analysed nationally-linked health data for all adult New Zealanders, including all publicly funded hospitalisation, outpatient, medicines, laboratory and primary care over seven years (July 1, 2007 - June 30, 2014).
They calculated annual health spending per person and analysed the association of this spending to whether a person had any of six chronic diseases - cancer, cardiovascular disease, diabetes, musculoskeletal, neurological and lung/liver/kidney diseases - or a combination of any of them.
Apart from the "extra'' co-morbidity costs, the remaining three quarters of spending on chronic diseases consisted of heart disease and stroke (18.7%), musculoskeletal disorders (16.2%), neurological conditions (14.4%), cancer (14.1%), lung/liver/kidney disease (7.4%), and diabetes ( 5.5%).