P4-17. Excess costs of non-infectious comorbidities among people living with HIV – estimates from Denmark, Sweden and Norway

Frida Hjalte [1], Paul S. Calara [1], Anders Blaxhult [2], Marie Helleberg [3], Karoline Wallace [4], Peter Lindgren [1,5]
Affiliates: [1] The Swedish Institute for Health Economics (IHE), Lund, Sweden. [2] Venhälsan, Department of Infectious Diseases, Södersjukhuset, Stockholm, Sweden. [3] Center of Excellence for Health, Immunity and Infections, Department of Infectious Diseases, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark. [4] Gilead Sciences, Solna, Sweden. [5] Department of Learning, Informatics, Management and Ethics, Karolinska Institutet, Stockholm, Sweden.

Background
People living with HIV (PLHIV) have an increased risk of comorbidities with non-communicable diseases such as cardiovascular disease, chronic kidney disease and osteoporotic fractures, compared to the general population. After the introduction of effective combination antiretroviral therapy (cART) the life expectancy of PLHIV has improved and is now approaching that of the general population. As the HIV-infected population ages the burden of comorbidities is expected to rise.
The prevalence of comorbidities may be associated with substantial costs for society but to date there have been limited studies on the costs and resource utilization associated with comorbidities among PLHIV.
The objective of this study was to estimate the excess cost of myocardial infarction, stroke, osteoporotic fractures and chronic kidney disease among HIV-infected persons in Denmark, Sweden and Norway.

Methods
The population attributed risk approach (PAR) approach was used to analyse the impact of HIV on the share of the total costs of a given comorbidity. Excess direct costs (medical resource utilization) and indirect costs (production loss) for one year were calculated for myocardial infarction, stroke, osteoporotic fractures and chronic kidney disease. These costs were calculated separately for Denmark, Sweden and Norway for each of the four comorbidities and stratified by age and sex. First, the total cost of illness (COI) for each comorbidity in the Danish, Swedish and Norwegian population was derived by multiplying the number of cases in one year with the associated average cost per patient. Next, the proportion of the COI attributable to HIV was calculated using the PAR approach to estimate the number of patients with a particular comorbidity and HIV. The PAR equation was informed by relative risks reported from a Danish cohort study and HIV prevalence data relevant for each country. The COI for each comorbidity was then multiplied by the corresponding PAR estimate in order to derive the excess cost attributed to HIV. Country-specific sources of epidemiological and cost data were used when available.

Results
The excess direct and indirect costs per HIV-infected person in the course of one year for myocardial infarction, stroke, osteoporotic fractures and chronic kidney disease attributable to HIV was estimated to €520 in Denmark, €390 in Sweden and €360 in Norway. This results in an estimated total excess cost of €3.4 million for Denmark, €2.6 million for Sweden and €2.0 million for Norway for one year. Chronic kidney disease accounted for around 65 percent of the total excess costs, followed by osteoporotic fractures which accounted for approximately 16 percent. Myocardial infarction and stroke had least impact on total excess costs, around 12 and 7 percent respectively. The total excess costs were highest in the 50-59 year old age group.

Conclusions
The high prevalence of comorbidities in the HIV-infected population is associated with excess costs. These costs are likely to increase over time as the number of older HIV-infected persons continues to grow. Additional studies are needed to give more insights to the extent and the predictors of these excess costs. Also, studies on the impact and cost-effectiveness of prophylactic interventions, as well as any methods to improve early diagnosis and treatment of comorbidities among PLHIV are warranted.