The economic burden of kidney disorders in Korea

Abstract

Aims: To estimate the economic burden of kidney disorders in Korea.

Materials and methods: The economic burden of kidney disorders was estimated using a prevalence-based approach. Related kidney diseases in patients with kidney disorders (RPWKD) were defined using codes from the tenth International Classification of Disease (E70–E90, F30–F48, F60–F69, F90–F99, K65–K67, N00–N08, N17–N19, and N30–N39). All diseases in patients with kidney disorders (APWKD) were defined as kidney disorders that involved all disease codes. Economic costs were divided into direct costs (medical costs and non-medical costs) and indirect costs (productivity loss because of morbidity and premature mortality).

Results: The prevalence of kidney disorders increased from 0.08% (2008) to 0.11% (2011). The total economic burden of RPWKD also substantially increased from $898.9 million (2008) to $1.43 billion (2011). This ∼59.4% increase in the economic burden was equal to 0.12% of the Korean gross domestic product. The economic burden of APWKD also increased during the study period: $1.06 billion (2008), $1.23 billion (2009), $1.44 billion (2010), and $1.46 billion (2011).

Conclusions: The present study provides the first data regarding the economic burden of kidney disorders in Korea. The findings support the need for early intervention services and prevention programs to prevent, identify, and manage kidney disorders.

Keywords:

• Kidney disorders
• economic burden
• cost analysis
• prevalence-based approach
• Korea

Introduction

Korea has a disability registry system¹. There were 2,494,460 registered disabled individuals in 2014². Kidney disorder is a type of disability and the number registered with kidney disorder was 70,434 (2.82%)². Furthermore, this increased from 60,110 in 2011 to 70,434 in 2014. According to the Act on welfare of persons with disabilities in Korea, kidney disorders were defined as chronic renal failure (ICD-10: N18) requiring hemodialysis, peritoneal dialysis for more than 1 month, or continuous treatment through kidney transplantation¹.

There are various causes of kidney disorders, although the primary cause is chronic kidney disease. In Japan, the prevalence of chronic kidney disease among adults is estimated as ∼19.1% (19 million people)³. The prevalence of chronic kidney disease in over 35-year-old Korean urban people is 13.8%⁴, which is similar to global prevalence (8–16%)⁵, but higher than US prevalence (11%)⁶. In Australia, 11.2% of the population has stage ≥3 chronic kidney disease⁷. The number of kidney disease cases has increased from 72,000 in 2007 to 158,000 in 2014, with an average annual increase of 11.8% during those 7 years⁸, in Korea.

The increasing prevalence of chronic kidney disease is associated with reduced quality-of-life and increased healthcare costs⁹.

With an aging society, the incidence and prevalence of chronic disease will be increased. Therefore, the prevalence of chronic kidney disease as one of the chronic diseases will be increased in the elderly population^10,11. These increases will generate increasing medical costs and economic burdens, which warrants a better understanding of these factors.

In the US, patients with chronic kidney disease have 1.8-fold greater medical costs, compared to patients without chronic kidney disease. Furthermore, in 2010, the 65 million patients with end-stage kidney disease were expected to generate > $280 billion in medical costs¹². In Australia, the medical costs of chronic kidney disease equal ∼5.7% of total medical costs⁷. Similarly, Korea has an alarming economic burden that is associated with chronic kidney disease, with total direct and indirect costs estimated at >5,000 billion Korean won (∼ $5 billion) in 2011. Moreover, the total economic burden of kidney disorders in 2011 was equal to ∼0.4% of the Korean gross domestic product ($1,162 billion)¹³. The total economic burden of chronic kidney disease had increased from $609.1 million (2007) to $1.28 billion (2014), with an annual growth rate of 11.2%⁸. Thus, the costs of chronic kidney disease are substantial.

The economic burden and medical costs that are associated with chronic kidney disease are related to the estimated kidney replacement costs^14–20 and the estimated costs to society because of productivity loss¹³. However, to the best of our knowledge, no studies have evaluated the economic burden of kidney disorders in Korea. Therefore, the present study aimed to evaluate this burden and its trend, by analyzing data from the health insurance database and causes of death from the Korean National Statistical Office.

Methods

Data sources and methods

The economic burden of kidney disorders was estimated using a prevalence-based approach. Since 1988, Korea has maintained a National Disability Registry (NDR) that includes individuals with kidney disorders, where the population’s disability types and severities are recorded by local governments. There are currently 15 types of disability, which are graded using a severity scale of 1–6¹. Therefore, we were able to search the database for individuals with kidney disorders who were registered between 2008 and 2011.

In this study, we had the operational definition of RPWKD. RPWKD divided into primary and secondary disease. Primary disease was a disease leading directly to the kidney disorders and secondary disease meant a disease caused by the persistence of the kidney disorders. For selecting the RPWKD, we reviewed the clinical theories of chronic kidney disease and consulted with an internist.

We used blocks of categories of the tenth International Classification of Disease (ICD-10) recommended by WHO (May, 1990). Selected disease categories are E70–E90, F30–F48, F60–F69, F90–F99, K65–K67, N00–N08, N17–N19, and N30–N39. In addition, the NDR is linked to the database of the Korean National Health Insurance Corporation (NHIC), which allowed us to examine the related direct medical costs. In this context, Korea has a national health insurance system that is exclusively administered by the NHIC, which can provide nationally representative claims data regarding medical care costs¹⁴. However, the NHIC claims data do not include non-covered indirect costs. Therefore, we connected data from the NDR to causes of death data from the Korean National Statistical Office. Based on the 2011 national survey of persons with disabilities (Ministry of Employment and Labor survey regarding labor conditions)²¹, we were also able to estimate the indirect costs of kidney disorders. Therefore, we were able to calculate the direct costs (medical and non-medical costs) and indirect costs (lost productivity from morbidity and premature mortality) that were associated with kidney disorders.

The resources for this study are summarized in Table 1. Indirect costs (i.e. lost productivity) were calculated by applying an annual discount rate of 3%. All costs were converted from Korean won into US dollars ($1 = 1,127.5 won). Based on the annual consumer price index, all costs were applied inflation each year. This study’s design was approved by the Institutional Review Board of the Korean National Rehabilitation Center (NRC-2014-04-027). All statistical analyses were performed using SAS software (version 9.4; SAS Institute Inc., Cary, NC).

Table 1. Data source.

Cost item	Resource
Direct costs
Direct medical costs
Inpatient care costs  Outpatient care costs	The Korea National Health Insurance Corporation (KNHIC) (2008 ∼ 2011)
Non-covered services costs	N Rehabilitation Hospital in Seoul (2008 ∼ 2011)
Assistive device costs	National Survey on Persons with disabilities (2011)
Direct non-medical costs
Transportation costs	National Survey on Persons with disabilities (2011)
Nursing costs	National Survey on Persons with disabilities (2011)
Indirect costs
Productivity costs (productivity loss due to morbidity)	Ministry of Employment and Labor Statistics’ survey report on labor conditions (2008 ∼ 2011) National Survey on Persons with disabilities (2011)
Premature death costs (productivity loss due to premature mortality)	The Korea National Statistical Offices’ records of causes of death (2008 ∼ 2011) National Survey on Persons with disabilities (2011)

Direct costs

Direct costs that were associated with kidney disorders included medical costs that were covered by the NHIC (costs related to inpatient and outpatient treatment), costs of assistive devices, and costs that were not covered by the NHIC.

Direct medical costs

Direct medical costs of healthcare for kidney disorders as the primary disease were calculated by extracting data from the NHIC (2008–2011). However, these data are inherently limited, as they only account for costs that are covered to healthcare providers for insurance-covered services. The costs of non-covered services were estimated by applying the percentage of non-covered services (10.8%) at a Korean national rehabilitation hospital in 2012. The costs of purchasing and maintaining assistive devices for kidney disorders were estimated as $691.69 using the survey on disabilities (2011). This was calculated using the annual consumer price index (Supplementary 1). In the following equation, DMC was defined as the direct medical costs, IC was defined as inpatient costs, NCR_i was defined as non-covered inpatient costs, OC was defined as outpatient costs, NCR_o was defined as non-covered outpatient costs, and RC was defined as the costs of rehabilitation and assistive devices. $$\mathrm{A}\mathrm{n}\mathrm{n}\mathrm{u}\mathrm{a}\mathrm{l}\mathrm{ }\mathrm{d}\mathrm{i}\mathrm{r}\mathrm{e}\mathrm{c}\mathrm{t}\mathrm{ }\mathrm{m}\mathrm{e}\mathrm{d}\mathrm{i}\mathrm{c}\mathrm{a}\mathrm{l}\mathrm{ }\mathrm{c}\mathrm{o}\mathrm{s}\mathrm{t}\mathrm{s}=\mathrm{ }\sum _{\mathrm{m}=1}^{12}{\mathrm{D}\mathrm{M}\mathrm{C}}_{\mathrm{m}}$$ (1) $$\mathrm{D}\mathrm{M}\mathrm{C}=\left[{\mathrm{I}\mathrm{C}}_{\mathrm{m}}+\frac{\left({\mathrm{I}\mathrm{C}}_{\mathrm{m}}\mathrm{ }\times \mathrm{ }{\mathrm{N}\mathrm{C}\mathrm{R}}_{\mathrm{i}}\right)}{\left(1\mathrm{ }-\mathrm{ }{\mathrm{N}\mathrm{C}\mathrm{R}}_{\mathrm{i}}\right)}\right]+\left[{\mathrm{O}\mathrm{C}}_{\mathrm{i}}+\frac{\left({\mathrm{O}\mathrm{C}}_{\mathrm{m}}\mathrm{ }\times \mathrm{ }{\mathrm{N}\mathrm{C}\mathrm{R}}_{\mathrm{o}}\right)}{\left(1\mathrm{ }-\mathrm{ }{\mathrm{N}\mathrm{C}\mathrm{R}}_{\mathrm{o}}\right)}\right]+{\mathrm{R}\mathrm{C}}_{\mathrm{m}}$$(1)

Direct non-medical costs

Direct non-medical costs were defined as transportation and nursing costs, which were obtained from the 2011 national survey of persons with disabilities. The nursing cost is the cost of hiring caregivers or cared by the family (Supplementary 1). One-way transportation costs were defined as $1.71 and were multiplied by the number of clinic visits for both inpatients and outpatients, which was based on the assumption that the guardian accompanied the patient (Supplementary 1). Inpatient nursing costs were estimated by the number of inpatient days multiplied by the daily nursing costs, and outpatient nursing costs were estimated as being 1/3 of the corresponding costs for inpatient nursing²². The total nursing costs were calculated by adding the inpatient and outpatient nursing costs. In the following equation, NMC was defined as the direct non-medical costs, TF_i was defined as the one-way transportation costs for inpatients, TF_o was defined as the one-way transportation costs for outpatients, F_i,ag was defined as the frequency of inpatient stays per age group, F_o,ag was defined as the frequency of outpatient visits per age group, WC was defined as the caregiver’s wage, and I_each year/2011 was defined as the price index for each year as a proportion of the price index in 2011. $$\mathrm{A}\mathrm{n}\mathrm{n}\mathrm{u}\mathrm{a}\mathrm{l}\mathrm{ }\mathrm{d}\mathrm{i}\mathrm{r}\mathrm{e}\mathrm{c}\mathrm{t}\mathrm{ }\mathrm{n}\mathrm{o}\mathrm{n}-\mathrm{m}\mathrm{e}\mathrm{d}\mathrm{i}\mathrm{c}\mathrm{a}\mathrm{l}\mathrm{ }\mathrm{c}\mathrm{o}\mathrm{s}\mathrm{t}\mathrm{s}=\mathrm{ }\sum _{\mathrm{m}=1}^{12}{\mathrm{N}\mathrm{M}\mathrm{C}}_{\mathrm{m}}$$ (2) $$\mathrm{N}\mathrm{M}\mathrm{C}=\sum _{\mathrm{a}\mathrm{g}=0}^9{(\mathrm{T}\mathrm{F}}_{\mathrm{i}}\times {\mathrm{F}}_{\mathrm{i},\mathrm{\hspace{0.17em}}\mathrm{a}\mathrm{g}}\times 2\times \raisebox{1ex}{${\mathrm{I}}_{\mathrm{e}\mathrm{a}\mathrm{c}\mathrm{h}\mathrm{\hspace{0.17em}}\mathrm{y}\mathrm{e}\mathrm{a}\mathrm{r}}$}\!\left/ \!\raisebox{-1ex}{$2011$}\right.)+\mathrm{\hspace{0.17em}}\sum _{\mathrm{a}\mathrm{g}=0}^9\left({\mathrm{T}\mathrm{F}}_{\mathrm{o}}\times {\mathrm{F}}_{\mathrm{o},\mathrm{\hspace{0.17em}}\mathrm{a}\mathrm{g}}\times 2\times \raisebox{1ex}{${\mathrm{I}}_{\mathrm{e}\mathrm{a}\mathrm{c}\mathrm{h}\mathrm{\hspace{0.17em}}\mathrm{y}\mathrm{e}\mathrm{a}\mathrm{r}}$}\!\left/ \!\raisebox{-1ex}{$2011$}\right.\right)+\sum _{\mathrm{a}\mathrm{g}=0}^9\left(\mathrm{W}\mathrm{C}\times {\mathrm{T}\mathrm{F}}_{\mathrm{i},\mathrm{\hspace{0.17em}}\mathrm{a}\mathrm{g}}\times \raisebox{1ex}{${\mathrm{I}}_{\mathrm{e}\mathrm{a}\mathrm{c}\mathrm{h}\mathrm{\hspace{0.17em}}\mathrm{y}\mathrm{e}\mathrm{a}\mathrm{r}}$}\!\left/ \!\raisebox{-1ex}{$2011$}\right.\right)+\sum _{\mathrm{a}\mathrm{g}=0}^9\left(\mathrm{W}\mathrm{C}\times {\mathrm{F}\mathrm{C}}_{\mathrm{o},\mathrm{\hspace{0.17em}}\mathrm{a}\mathrm{g}}\times \raisebox{1ex}{${\mathrm{I}}_{\mathrm{e}\mathrm{a}\mathrm{c}\mathrm{h}\mathrm{\hspace{0.17em}}\mathrm{y}\mathrm{e}\mathrm{a}\mathrm{r}}$}\!\left/ \!\raisebox{-1ex}{$2011$}\right.\times \frac{1}{3}\right)$$(2)

Indirect costs

Indirect costs were evaluated based on the human capital approach, in which the opportunity costs of morbidity and mortality are quantified as productivity loss related to absence from work (because of hospitalization and/or outpatient visits) and premature death²³. Disability wages were applied to the internal disabled average salary. Individuals who were 0–19 and ≥70 years old were excluded from these calculations, as they were not expected to participate in economic activity. Thus, our calculations only considered individuals who were 20–69 years old (Supplementary 2).

Productivity loss related to morbidity

Inpatient productivity costs were calculated by multiplying the days of hospitalization and the average salary. Outpatient productivity costs were calculated by multiplying the number of outpatient visits by the average visit time and the average salary. The average time for outpatient visits was defined as 3 h (including travel time), and this value was assumed to be 1/3 of working time²².

Productivity loss related to premature death

The productivity loss cost due to premature death was defined as expected income until 69-year-old if they alive. We searched the databases for records of disability-related deaths (according to each disability type), and calculated the corresponding productivity losses from premature death. Expected future earnings were discounted by 3% annually, to reflect the present value of future productivity²⁴.

The economic burden of all diseases in patients with kidney disorders (APWKD)

We also performed analysis of the economic burden of all disease that includes all healthcare utilization data used by PWPD.

Sensitivity analysis

We performed two sensitivity analyses to estimating the indirect cost. (1) An annual discount rate was adjusted from 3% to 5% for estimating the costs of productivity loss of premature death. (2) The individual’s wage replaced disabilities wage with non-disabilities wage for estimating the costs of productivity lost. The wage of the non-disabled is based on the survey data on the wage structure of the National Statistical Office (Supplementary 3).

Results

Prevalence of treatment for kidney disorders

Our analyses revealed that, in 2011, there were 53,347 cases of related kidney diseases in patients with kidney disorders (RPWKD), which was a 36% increase compared to the 39,266 cases in 2008. The prevalence of treatment increased by 33.95% from 79.48/100,000 population in 2008 to 106.46/100,000 population in 2011. The prevalence of treatment was highest among individuals who were 50–59 years old and 60–69 years old during all four study years (2008–2011) (Table 2).

Table 2. Treated prevalence of people with kidney disorders in Korea in 2008–2011 (unit: per 100,000) prevalence rate at the end of the year.

Age group (years)	Year
	2008			2009			2010			2011
	Male	Female	All	Male	Female	All	Male	Female	All	Male	Female	All
0 ∼ 9	1.04	0.88	0.96	1.04	0.87	0.96	0.96	0.73	0.85	0.90	0.57	0.74
10 ∼ 19	5.57	3.27	4.49	5.30	3.48	4.44	4.45	3.02	3.77	4.28	3.26	3.80
20 ∼ 29	23.62	14.79	19.34	22.89	14.02	18.61	20.83	13.91	17.50	18.87	12.75	15.93
30 ∼ 39	65.91	46.52	56.40	66.98	48.19	57.77	65.47	45.61	55.74	62.94	44.83	54.06
40 ∼ 49	122.41	94.55	108.73	126.79	96.02	111.67	126.70	96.27	111.75	127.53	95.95	112.03
50 ∼ 59	198.99	161.50	180.28	214.81	171.05	192.99	226.39	174.34	200.41	236.02	177.84	206.96
60 ∼ 69	248.36	180.79	212.55	291.39	209.95	248.47	322.88	230.81	274.61	352.25	253.61	300.76
70 ∼ 79	188.90	107.88	137.61	251.88	143.74	183.84	313.35	174.60	226.54	399.65	218.32	286.83
Total	88.89	70.03	79.48	100.15	78.60	89.40	109.23	84.85	97.06	119.98	92.90	106.46

RPWKD economic burden

The total economic burden of kidney disorders in 2011 was $1.43 billion, which was a 1.59-fold increase from $898.9 million in 2008. The total economic burden of kidney disorders in 2011 accounted for 0.12% of the Korean gross domestic product ($1,162 billion) and 1.77% of national healthcare expenditures ($80.88 billion). The economic burdens per person were $22,890 in 2008, $23,490 in 2009, $25,300 in 2010, and $26,860 in 2011. The per capita annual medical costs were 26.62-fold greater than those of the general population ($914 in 2011).

Burdens according to gender, age, and cost item

During 2008–2011, men exhibited a 1.28–1.30-fold greater burden, compared to women. Women in their 60s exhibited the greatest burden in 2008–2009, although this changed to women in their 50s during 2010–2011. Patients who were 50–59 years old exhibited the greatest overall burden during the study period (2008–2011) (Table 3).

Table 3. Total economic burden of people with kidney disorders in Korea (unit: million US $).

Age group (years)	Year
	2008		2009		2010		2011
	Costs	%	Costs	%	Costs	%	Costs	%
Male
0–19	3.58	0.71	3.54	0.61	3.01	0.44	2.66	0.33
20–29	16.56	3.28	14.79	2.53	15.04	2.18	13.24	1.63
30–39	53.52	10.61	54.43	9.32	55.21	8.02	55.45	6.84
40–49	112.06	22.21	119.83	20.51	126.66	18.39	133.88	16.53
50–59	148.04	29.34	171.82	29.41	203.21	29.50	240.49	29.69
60–69	129.32	25.63	156.20	26.74	189.77	27.55	221.85	27.38
70+	41.45	8.22	63.57	10.88	95.84	13.92	142.53	17.59
Total	504.53	100	584.17	100	688.73	100	810.11	100
Female
0–19	2.22	0.56	2.32	0.51	2.25	0.42	2.08	0.33
20–29	9.35	2.37	8.71	1.90	8.37	1.56	8.33	1.34
30–39	36.78	9.33	36.23	7.90	36.48	6.81	37.49	6.02
40–49	82.36	20.88	85.44	18.64	90.94	16.97	93.61	15.03
50–59	114.72	29.09	133.50	29.12	149.49	27.89	169.58	27.23
60–69	105.13	26.66	126.09	27.50	151.05	28.18	173.81	27.91
70+	43.83	11.11	66.13	14.43	97.38	18.17	137.93	22.15
Total	394.39	100	458.42	100	535.96	100	622.83	100
All
0–19	5.80	0.65	5.85	0.56	5.26	0.43	4.75	0.33
20–29	25.91	2.88	23.50	2.25	23.41	1.91	21.58	1.51
30–39	90.31	10.05	90.65	8.70	91.69	7.49	92.94	6.49
40–49	194.42	21.63	205.27	19.69	217.60	17.77	227.49	15.88
50–59	262.76	29.23	305.33	29.29	352.69	28.80	410.07	28.62
60–69	234.44	26.08	282.29	27.08	340.82	27.83	395.66	27.61
70+	85.29	9.49	129.70	12.44	193.22	15.78	280.46	19.57
Total	898.93	100	1,042.60	100	1,224.69	100	1,432.94	100

During the study period, direct medical costs among women accounted for >80% of their total annual economic burden (80.29–84.09%). Among men, the proportion of direct medical costs increased during the study period: 76.56% in 2008, 78.38% in 2009, 80.89% in 2010, and 81.54% in 2011. Indirect costs among men accounted for 21.18% of their burden in 2008 and 15.81% in 2011. Indirect costs among women accounted for 17.37% of their burden in 2008 and 13.15% in 2011. The proportions for both men and women gradually decreased during the study period (Table 4).

Table 4. Cost of people with kidney disorders in Korea (unit: million US $).

Variable	Year
	2008		2009		2010		2011
	Costs	%	Costs	%	Costs	%	Costs	%
Male
Direct medical care	386.26	76.56	457.87	78.38	557.14	80.89	660.56	81.54
Paid by insurer	296.32	58.73	357.92	61.27	449.73	65.30	530.32	65.46
Copayment by patients	45.92	9.10	45.12	7.72	36.06	5.24	43.14	5.33
Non-covered services	35.79	7.09	43.24	7.40	54.35	7.89	64.08	7.91
Assistive devices	8.22	1.63	11.59	1.98	17.00	2.47	23.02	2.84
Direct non-medical care	11.40	2.26	13.97	2.39	17.31	2.51	21.50	2.65
Transportation	4.03	0.80	4.82	0.82	5.75	0.84	6.93	0.85
Nursing costs	7.36	1.46	9.15	1.57	11.56	1.68	14.57	1.80
Indirect	106.88	21.18	112.33	19.23	114.28	16.59	128.05	15.81
Lost productivity	12.84	2.54	15.77	2.70	19.63	2.85	23.76	2.93
Premature death	94.04	18.64	96.56	16.53	94.65	13.74	104.30	12.87
Total	504.53	100	584.17	100	688.73	100	810.11	100
Female
Direct medical care	316.64	80.29	372.57	81.27	445.41	83.10	523.74	84.09
Paid by insurer	241.19	61.16	288.97	63.04	357.20	66.65	417.20	66.98
Copayment by patients	39.08	9.91	38.33	8.36	30.28	5.65	35.90	5.76
Non-covered services	29.18	7.40	34.96	7.63	43.22	8.06	50.49	8.11
Assistive devices	7.18	1.82	10.31	2.25	14.71	2.74	20.15	3.24
Direct non-medical care	9.24	2.34	11.21	2.45	13.85	2.58	17.16	2.75
Transportation	3.19	0.81	3.70	0.81	4.33	0.81	5.13	0.82
Nursing costs	6.05	1.54	7.51	1.64	9.51	1.78	12.03	1.93
Indirect	68.51	17.37	74.64	16.28	76.70	14.31	81.93	13.15
Lost productivity	10.30	2.61	12.33	2.69	14.86	2.77	17.66	2.84
Premature death	58.21	14.76	62.31	13.59	61.85	11.54	64.27	10.32
Total	394.39	100.00	458.42	100.00	535.96	100.00	622.83	100.00
All
Direct medical care	702.9	78.19	830.44	79.65	1,002.55	81.86	1,184.30	82.65
Paid by insurer	537.52	59.80	646.9	62.05	806.94	65.89	947.52	66.12
Copayment by patients	85	9.46	83.45	8.00	66.34	5.42	79.05	5.52
Non-covered services	64.97	7.23	78.2	7.50	97.57	7.97	114.57	8.00
Assistive devices	15.41	1.71	21.89	2.10	31.71	2.59	43.17	3.01
Direct non-medical care	20.64	2.30	25.18	2.42	31.16	2.54	38.65	2.70
Transportation	7.22	0.80	8.52	0.82	10.08	0.82	12.05	0.84
Nursing costs	13.42	1.49	16.66	1.60	21.07	1.72	26.6	1.86
Indirect	175.39	19.51	186.97	17.93	190.98	15.59	209.99	14.65
Lost productivity	23.14	2.57	28.11	2.70	34.48	2.82	41.41	2.89
Premature death	152.25	16.94	158.87	15.24	156.5	12.78	168.57	11.76
Total	898.93	100	1,042.60	100	1,224.69	100	1,432.94	100

Among the cost items, the highest proportions were for direct medical costs during the study period: 78.19% in 2008, 79.65% in 2009, 81.86% in 2010, and 82.65% in 2011. The proportion of direct medical costs has increased. In contrast, the proportions of indirect costs decreased from 19.5% ($175.39 million) in 2008 to 14.7% ($209.99 million) in 2011 (Figure 1). Both direct and indirect medical costs have increased, but, due to the relatively low increase, the indirect medical costs ratio decreased.

Figure 1. Proportion of the annual economic burden between 2008 and 2011.

The proportion of direct costs in the total economic burden increased from 78.2% ($702.90 million) in 2008 to 82.6% ($1.18 billion) in 2011. Direct medical costs increased 1.87-fold from $20.64 million in 2008 to $38.65 million in 2011, while indirect medical costs increased 1.2-fold from $175.39 million in 2008 to $209.99 million in 2011. Most of the direct medical costs were covered by the insurer, and the covered proportion increased from 59.80% in 2008 to 66.12% in 2011. Patient co-payments decreased from 9.46% in 2008 to 5.52% in 2011. Lost productivity because of premature death accounted for the highest percentage of the economic burden (16.94% in 2008 and 11.76% in 2011) (Table 4).

APWKD economic burden

The prevalence of APWKD increased 1.36-fold from 44,093 persons in 2008 to 60,055 persons in 2011. Total costs for APWKD were $1.06 billion in 2008, $1.23 billion in 2009, $1.44 billion in 2010, and $1.46 billion in 2011. The cost of APWKD was 1.02-fold greater than the cost of RPWKD in 2011 ($1.46 billion vs $1.43 billion) (Table 5). The per capita economic burdens were $24,089 in 2008, $24,906 in 2009, $26,692 in 2010, and $24,316 in 2011. The per capita annual medical costs were 26.62-fold greater than those among the general population ($914 in 2011). The total costs of APWKD increased 137% from $1.06 billion in 2008 to $1.46 billion in 2011 (Table 5).

Table 5. Cost of people with kidney disorders in Korea (ALL) (unit: million US $).

Variable	Year
	2008		2009		2010		2011
	Costs	%	Costs	%	Costs	%	Costs	%
All
Direct medical care	850.81	80.04	1,001.23	81.28	1,199.38	83.14	1,201.60	82.28
Paid by insurer	638.53	60.12	764.07	62.02	945.42	65.54	945.42	64.74
copayment by patients	104.23	9.81	103.54	8.40	84.31	5.84	84.31	5.77
Non-covered services	77.14	7.26	92.31	7.49	114.26	7.92	114.26	7.82
Assistive devices	30.90	2.91	41.31	3.35	55.39	3.84	57.60	3.94
Direct non-medical care	27.66	2.60	33.77	2.74	40.92	2.84	21.50	1.47
Transportation	9.51	0.90	11.30	0.92	13.20	0.92	13.73	0.94
Nursing costs	18.15	1.71	22.47	1.82	27.72	1.92	28.83	1.97
Indirect	183.68	17.29	196.89	15.98	202.26	14.02	216.16	14.80
Lost productivity	31.42	2.96	38.03	3.09	45.76	3.17	47.59	3.26
Premature death	152.25	14.33	158.87	12.90	156.50	10.85	168.57	11.54
Total	1,062.14	100.00	1,231.89	100.00	1,442.56	100.00	1,460.32	100.00

Sensitivity analysis

The results of the sensitivity analyses are provided in Table 6. (1) Compared to the baseline analysis (discount rate 3%), applying a discount rate of 5% resulted in 2% decreases in total costs each year. (2) Using non-disabled individuals’ income, the total costs increased $1.59 billion in 2008 compared with base analysis. In 2011, that is an estimated $2.17 billion more than base analysis (Table 6).

Table 6. Sensitivity analysis of economic burden of people with kidney disorders in Korea (unit: million US $).

Year	Variable
	Direct medical costs	Direct non-medical costs	Indirect costs	Total	Difference with base analysis (%)
2008
Base analysis	702.90	20.64	175.39	898.93
Sensitivity analysis 1	702.90	20.64	153.57	877.10	–2%
Sensitivity analysis 2	702.90	20.64	866.16	1,589.69	77%
2009
Base analysis	830.44	25.18	186.97	1,042.60
Sensitivity analysis 1	830.44	25.18	164.52	1,020.14	–2%
Sensitivity analysis 2	830.44	31.79	860.37	1,715.99	65%
2010
Base analysis	1,002.55	31.16	190.98	1,224.69
Sensitivity analysis 1	1,002.55	31.16	169.10	1,202.81	–2%
Sensitivity analysis 2	1,002.55	31.16	865.64	1,899.34	55%
2011
Base analysis	1,184.30	38.65	209.99	1,432.94
Sensitivity analysis 1	1,184.30	38.65	186.47	1,409.42	–2%
Sensitivity analysis 2	1,184.30	38.65	950.72	2,173.68	52%

Base analysis: the costs of premature death were estimated with a discount rate of 3% (current standard discount rate)

Sensitivity analysis 1: the costs of premature death were estimated with a discount rate of 5%.

Sensitivity analysis 2: estimation of cost of lost productivity loss using non-disabled income.

Discussion

The present study used a prevalence-based approach to estimate the economic burden of kidney disorders based on data from Korean national databases (2008–2011). Our analyses revealed that the economic burden of 53,347 PWKD in 2011 was 35.86% greater than that of the 39,266 people in 2008, and the treated-prevalence rate increased by 33.95% from 79.48/100,000 population in 2008 to 106.46/100,000 population in 2011. The prevalence of RPWKD increased by 136% from 39,266 people in 2008 to 53,347 people in 2011.

The total economic burden of kidney disorders in 2011 was $1.43 billion, which was a 1.59-fold increase from $898.9 million in 2008. The total economic burden of kidney disorders in 2011 accounted for 0.12% of the Korean gross domestic product ($1,162 billion)²⁵ and 1.77% of national healthcare expenditures ($80.88 billion)⁸. In Korea, the total economic burden of kidney disorders during 2011 was similar to that of lung cancer in 2005 ($1.47 billion)²⁶. However, the economic burden of kidney disorders in 2011 was 1.59-fold greater than that in 2008, and chronic kidney disease had an estimated cost of > $5 billion in 2011¹³. Thus, the economic burden of chronic kidney disease in 2011 was 3.1-fold greater than that of RPWKD. This difference is not directly proportional to the number of people who are affected by each illness, as kidney disorders have unique costs of medical expenses after enrolment exemption. There are also differences in the medical costs for each chronic kidney disease-related code, such as end-stage kidney disease, kidney replacement therapy, and kidney transplantation. The difference in these results was that only the patients with kidney disease as a major cause were included in the study.

In Canada, the cost of chronic kidney disease totaled $1.9 billion in 2000²⁷, and the annual cost of chronic kidney disease (stages 3–5) in the UK during 2009–2010 accounted for 1.3% of the National Health Service expenditures¹⁹. In Australia, the total health expenditures for chronic kidney disease during 2004–2005 were AUD$> 89.87 billion, which was 1.7% of the health budget and similar to the expenditures in other Organization for Economic Co-operation and Development countries²⁸. Based on the present study, the costs of diseases related to kidney disease in Korea accounted for 1.77% of the national health expenditures. Although it is difficult to compare different studies’ findings, based on methodological and currency differences, we found that kidney disorders were associated with a relatively high disease burden.

Interestingly, men exhibited a 1.28–1.30-fold greater economic burden that was related to kidney disorders, compared to women. This is logical, because the NDR contains a greater proportion of men. Furthermore, the prevalence of chronic kidney failure among adult patients (> 20 years old) was 10.4% for men and 11.8% for women²⁹. Thus, the prevalence of chronic kidney disease is higher among Korean men, compared to Korean women, and similar results have been observed in Japan³⁰, Singapore³¹, and Iran³².

The greatest overall costs according to age group were observed among 50–59-year-old patients (men and women combined) and 50–59-year-old men. Hemodialysis, peritoneal dialysis, or kidney transplantation are considered kidney replacement therapy^33–35. These procedures are most common among people who are in their 50s, with procedures being more common in men than in women. In Korea, ∼ 78.2% of PWKD cases received hemodialysis or peritoneal dialysis, and patients in their 50s are most likely to receive start dialysis¹¹. Based on Korean organ transplant data, most kidney transplants were in their 50s³⁶. Therefore, it appears that the corresponding economic burden will continue to increase, based on the results of this study.

The socioeconomic cost of end-stage kidney failure in Canada was $1.9 billion in 2000. The proportions were 69% for direct medical costs ($1.3 billion), 23% for productivity loss costs ($434 million) because of death, and 8% for productivity loss costs ($149 million) because of morbidity. Furthermore, in the study of the Kidney Center in Italy, the annual socio-economics costs per person of chronic kidney disease (stages 4–5) patients were 55.8% direct medical costs, direct non-medical costs 37.3%, and indirect costs 6.8%.

This study also had the largest proportion of direct medical costs, which means that people with chronic kidney disease are thought to have greater healthcare utilization because of their continuous dialysis and treatment³⁷. In addition, if chronic kidney disease progresses and leads to decreased kidney function, the related costs can increase because of various complications, such as hypertension, anemia, malnutrition, bone disease, and neuropathy³⁸. Thus, to reduce economic costs, it is also necessary to prevent complications and establish policies for healthcare after the patient has developed chronic kidney disease.

Indirect costs decreased by 19.5% ($197.7 million) in 2008 and 14.7% ($236.7 million) in 2011. In addition, the lost productivity cost increased (2.96% to 3.26%), while the lost productivity cost because of death decreased (14.33% to 11.54%). Nevertheless, women exhibited a lower proportion of death-related lost productivity cost (10.32%) in 2011, compared to men (12.87%). This difference may be explained by the fact that Korean men are more likely to be employed and receive higher wages, compared to women^39,40.

In the present study, the economic burdens of APWKD were $1.06 billion in 2008, $1.23 billion in 2009, $1.44 billion in 2010, and $1.46 billion in 2011. In addition, the economic burden of APWKD was 1.91–18.16% greater than that of RPWKD in 2011. The economic burden per person with APWKD was $24,316, and the per-capita annual medical costs were 26.62-fold greater than those of the general population ($914 in 2011).

This study had several limitations. First, we excluded the pharmaceutical costs of outpatient prescriptions and applied non-covered service at a single center because we could not access the related data. Second, we only considered cases with a primary diagnosis of a kidney disorders, and the inclusion of cases with a secondary diagnosis would likely increase the estimated economic burden. Third, different researchers will have different opinions regarding the major diseases that are associated with disability, which can create bias in the calculation of the economic burden of disease. Finally, the results were not presented according to the primary diseases of kidney disorders, and further research is needed to address this issue.

Conclusions

The present study is the first to calculate the economic burden of PWKD in Korea from 2008 to 2011, using nationally representative data. We defined the major diseases that were related to disability and the corresponding disease burdens. Thus, our findings could be used to establish policies that can help decrease the medical expenses of registered persons with disabilities. The economic burden of kidney disorders increased during the 4-year study period, and it is expected to steadily increase because of the aging population. Thus, proactively addressing the causes of disease before the development of disabilities is an important approach to reducing their economic burden. Furthermore, it is necessary to continuously manage health costs according to the characteristics of patients with the disorder (e.g. according to age, gender, and disease type). Further studies are needed to examine the medical costs of patients with disabilities, the development of secondary diseases, and the cost-effectiveness of medical services according to disability type. Policies are also needed to reduce the economic burden of disability and to improve health outcomes.

Transparency

Declaration of funding

This study was funded by Grant #14-A-03 from the Korea National Rehabilitation Research Institute.

Declaration of financial/other interests

The authors have no conflicts of interest to disclose. JME peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Acknowledgments

The study’s design was approved by the Institutional Review Board of the Korea National Rehabilitation Center.