There is little systematic assessment of how total health expenditure is distributed across diseases and comorbidities. The objective of this study was to use statistical methods to disaggregate all publicly funded health expenditure by disease and comorbidities in order to answer three research questions: (1) What is health expenditure by disease phase for noncommunicable diseases (NCDs) in New Zealand? (2) Is the cost of having two NCDs more or less than that expected given the independent costs of each NCD? (3) How is total health spending disaggregated by NCDs across age and by sex? Methods and findings
We used linked data for all adult New Zealanders for publicly funded events, including hospitalisation, outpatient, pharmaceutical, laboratory testing, and primary care from 1 July 2007 to 30 June 2014. These data include 18.9 million person-years and $26.4 billion in spending (US$ 2016). We used case definition algorithms to identify if a person had any of six NCDs (cancer, cardiovascular disease [CVD], diabetes, musculoskeletal, neurological, and a chronic lung/liver/kidney [LLK] disease). Indicator variables were used to identify the presence of any of the 15 possible comorbidity pairings of these six NCDs. Regression was used to estimate excess annual health expenditure per person. Cause deletion methods were used to estimate total population expenditure by disease. A majority (59%) of health expenditure was attributable to NCDs. Expenditure due to diseases was generally highest in the year of diagnosis and year of death. A person having two diseases simultaneously generally had greater health expenditure than the expected sum of having the diseases separately, for all 15 comorbidity pairs except the CVD-cancer pair. For example, a 60–64-year-old female with none of the six NCDs had $633 per annum expenditure. If she had both CVD and chronic LLK, additional expenditure for CVD separately was $6,443/$839/$9,225 for the first year of diagnosis/prevalent years/last year of life if dying of CVD; additional expenditure for chronic LLK separately was $6,443/$1,291/$9,051; and the additional comorbidity expenditure of having both CVD and LLK was $2,456 (95% confidence interval [CI] $2,238–$2,674). The pattern was similar for males (e.g., additional comorbidity expenditure for a 60–64-year-old male with CVD and chronic LLK was $2,498 [95% CI $2,264–$2,632]). In addition to this, the excess comorbidity costs for a person with two diseases was greater at younger ages, e.g., excess expenditure for 45–49-year-old males with CVD and chronic LLK was 10 times higher than for 75–79-year-old males and six times higher for females. At the population level, 23.8% of total health expenditure was attributable to higher costs of having one of the 15 comorbidity pairs over and above the six NCDs separately; of the remaining expenditure, CVD accounted for 18.7%, followed by musculoskeletal (16.2%), neurological (14.4%), cancer (14.1%), chronic LLK disease (7.4%), and diabetes (5.5%). Major limitations included incomplete linkage to all costed events (although these were largely non-NCD events) and missing private expenditure.
The costs of having two NCDs simultaneously is typically superadditive, and more so for younger adults. Neurological and musculoskeletal diseases contributed the largest health system costs, in accord with burden of disease studies finding that they contribute large morbidity. Just as burden of disease methodology has advanced the understanding of disease burden, there is a need to create disease-based costing studies that facilitate the disaggregation of health budgets at a national level. Author summary
Few studies have estimated disease-specific health system expenditure for many diseases simultaneously, keeping within the total envelope of health expenditure. Most cost of illness studies focus on a single or small set of disease(s) and overestimate costs due to attribution of comorbidities.
Few studies have estimated whether having two or more diseases increases or decreases health system expenditure, over and above that expected from having the diseases separately.
What did the researchers do and find?
Using nationally linked health data for all New Zealanders, the additional or excess costs from having one or more chronic diseases were calculated using regression equations.
Nearly a quarter of all health expenditure (23.8%) on chronic noncommunicable disease was attributable to costs from having two or more diseases (i.e., costs due to comorbid conditions, over and above separate costs from single diseases).
Of the remaining three quarters of health expenditure, its attribution across six chronic diseases (as though they were the only disease a person had) were: heart disease and stroke, 18.7%; musculoskeletal, 16.2%; neurological, 14.4%; cancer, 14.1%; chronic lung, liver, or kidney disease, 7.4%; and diabetes, 5.5%.
Health system expenditure due to musculoskeletal and neurological diseases is sizeable, suggesting these diseases need more policy and planning consideration and research than they currently receive.
The additional costs from having two or more diseases, over and above the costs of having disease separately, reinforce the need for policy and planning to anticipate the effects of aging populations with comorbidity.
Click here to view original web page at Health system costs for individual and comorbid noncommunicable diseases: An analysis of publicly funded health events from New Zealand