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Keywords:

  • Cost;
  • Osteoarthritis;
  • Chinese;
  • Joint replacement

Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. SUBJECTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES

Objective

To determine the direct and indirect cost of osteoarthritis (OA) according to disease severity, and to estimate the total cost of the disease in Hong Kong.

Methods

This study is a retrospective, cross-sectional, nonrandom, cohort design, with subjects stratified according to disease severity based on functional limitation and the presence or absence of joint prosthesis. Subjects were recruited from primary care, geriatric medicine, rheumatology, and orthopedic clinics. There were 219 patients in the mild disease category, 290 patients in the severe category, and 65 patients with joint replacement. A questionnaire gathered information on demographic and socioeconomic characteristics, function limitation, use of health and social services, and effect on occupation and living arrangements over the previous 12 months. Costs were calculated as direct and indirect.

Results

Low education and socioeconomic class were associated with more severe disease. OA affected family or close relationships in 44%. The average cost incurred as a result of side effects of medication is similar to the average cost of medication itself. Excluding joint replacement, the direct costs ranged from Hong Kong (HK) dollar $11,690 to $40,180 per person per year and indirect costs, HK $3,300–$6,640. The direct costs are comparable to those reported in Western countries; however, the ratio of direct to indirect costs is much higher than 1, in contrast to the greater indirect versus direct costs reported in whites. The total cost expressed as a percentage of gross national product is also much lower in Hong Kong.

Conclusions

The socioeconomic impact of OA in the Hong Kong population is comparable to Western countries, but the economic burden is largely placed on the government, with patients having relatively low out-of-pocket expenditures.


INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. SUBJECTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES

Osteoarthritis (OA) constitutes a major disease and disability burden worldwide, particularly in aging populations in developed regions, being the fifth largest contributor to disability life years (1). Osteoarthritis is probably the most common form of arthritis in Hong Kong, although there are no well-designed epidemiologic studies to document this. Nevertheless, with the graying of the population, the number of people with OA may be expected to increase. For example, a 1991 stratified random survey of the Hong Kong population aged 70 years and older showed that arthritis was the most common medical condition, affecting 30% of this age group, and was more common in women (40%) than men (12%) (2). Of those with joint pain, 68% of women and 42% of men reported limitation in activities as a result. The most common sites of joint pain in order of frequency were knees, back (thoracic and lumber regions), ankle/foot, and shoulder. Joint pain was associated with functional impairment, depressive symptoms, increased doctor consultations, and sleep problems. The use of nonsteroidal antiinflammatory drugs (NSAIDs) varied from 6% to 17% depending on age and sex (3). Although it is uncertain what proportion of NSAID use is due to OA, it is likely that this represents a large proportion, particularly in the older population. It has also been estimated that about 4% of hospital admission is due to adverse drug reactions, NSAIDs being 1 of the 3 most common drug classes giving rise to these adverse drug reactions (4). It is also a major risk factor for gastrointestinal hemorrhage (5).

Despite the magnitude of the problem, little attention has been drawn to the disease because there is a tendency to regard it as an inevitable part of aging and because of the limited therapeutic options available. Although studies have been carried out to examine the risk factors for OA (6), no data is available regarding the socioeconomic impact of the disease on the Hong Kong Chinese population. Although the cost incurred in the treatment of OA may be less than other forms of arthritis, such as rheumatoid arthritis, the greater prevalence of OA makes it more costly to health care providers (7). In many countries, OA has been estimated to incur significant economic, social, and psychological costs (8). A study was carried out in Hong Kong to estimate the direct, indirect, and intangible cost of OA. The estimates of direct costs, indirect costs, and social impact of the disease are reported here.

SUBJECTS AND METHODS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. SUBJECTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES

This study is a retrospective, cross-sectional, nonrandom, cohort design, with the subjects stratified by disease severity and presence or absence of joint prosthesis. To ensure that the sample would consist of sufficient numbers of patients with varying degrees of disease severity as well as those who have had joint replacement surgery, a convenience sample of patients with a diagnosis of OA were recruited from 4 different types of clinic (family medicine, rheumatology, orthopedics, and geriatric medicine) in 3 different geographic regions of Hong Kong. Subjects who were not able to respond to a questionnaire (e.g., as a result of aphasia from stroke, presence of dementia) were excluded. Consecutive subjects in each of these clinics were identified by the clinic doctor from a review of the charts and referred to the interviewer. After informed consent, a questionnaire was administered by the interviewer during clinic attendance. All patients approached participated. The questionnaire consisted of information on demographic and socioeconomic characteristics, duration of OA, and information on disease severity based on functional limitation (American College of Rheumatology 1991 revised criteria [9]). Patients were classified as having mild disease if their functional status was class I (able to perform usual activities of daily living, including self care, vocational, and avocational) or class II (limitation in avocational activities), and severe if the functional status was class III (able to perform usual self care activities, but limited in vocational and avocational activities) or class IV (limited in ability to perform usual self care, vocational, and avocational activities).

Hong Kong has a dual system with public and private provision for both ambulatory and hospital inpatient care. Public care is heavily subsidized, with patients usually paying Hong Kong (HK) $29 (HK $1 = US $0.128) for a general outpatient consultation, HK $44 for a specialist outpatient consultation, and HK $68 per inpatient day for general wards in public hospitals. Fee income accounts for only about 2.5% of the recurrent operating expenses in public hospitals (10). In the private sector, fees run from HK $145 to HK $350 per outpatient consultation depending on the location and specialty of the physician services, and HK $500–$3,600 for bed charge per inpatient day in private hospitals depending on ward class and specialties (11). In the survey, we obtained information on the types of healthcare facilities the patient had been utilizing, including both private and public care; if the patient utilized a private facility, we recorded the fees reported by the patients. For public care, nominal charges were not a good measure of economic costs because care was heavily subsidized. We thus used average per diem cost estimated by the government authority as a measure of cost to the public care provider.

Details relating to direct cost of the disease were collected for the previous 12 months, consisting of use of all types of hospital or clinic services (investigations, drug or nondrug treatments, transport to hospital or clinic, social services support, need for employment of care taker, need for residential care, use of alternative medicine). Details of direct costs cover both societal and individual perspectives. Cost estimates for service units provided by the government are obtained from government sources. Direct cost estimates also include patients' out-of-pocket expenses incurred in relation to the illness. These include travelling expenses, money spent on purchasing arthritis aids or home alterations, and hospital inpatient and outpatient charges. Information relating to indirect cost estimates include days of sick leave because of the disease, days off work incurred by relatives or friends in helping the patient, and loss of job because of the disease. We used the human capital approach to assess productivity loss. Information regarding patients' individual wage rates was obtained. If patients changed jobs due to OA, the difference between preceding wage rates and ensuing wage rates was calculated to measure the productivity loss. If patients quit their jobs due to OA, the lost earnings based upon preceding wage rates were calculated as productivity loss. Two specific questions to assess the social impact of the disease were included: “Does your osteoarthritis affect your family or other close relationships?” and “Did your osteoarthritis cause you to change your living arrangements?” These questions had been included in an Australian study on patient expenditures and social impact of living with OA, and inclusion of these questions enables a comparison between Hong Kong Chinese and Australians (12).

Costs were calculated separately as direct and indirect. They were further subdivided into costs for the government, costs borne by the patient (out-of-pocket expenses), various categories of expenditure, and by disease severity and joint replacement groups. Based on prevalence data of OA for Hong Kong, the total cost to the government incurred by the disease is estimated by multiplying the cost per subject calculated in this study by the estimated total number of people with different disease severity and joint replacement. The total cost is also expressed as a percentage of the gross national product (GNP). To consider the impact of varying assumptions of prevalence on overall costs, the cost estimation based on the prevalence of knee OA was further assessed in sensitivity analyses. We conducted a 2-way sensitivity analysis, allowing the assumption on fraction of severe OA to vary by 5 percentage points, and proportion of OA patients who seek help to vary by 10 percentage points.

Statistical analysis.

Patient information was recorded and the database was constructed initially in a Microsoft (Redmond, WA) Excel spreadsheet. Data and statistical analysis was performed in SAS (Cary, NC) (13). Overall, there were 574 patients each with 719 variables on socioeconomic, morbidity, health, and various healthcare resource uses. Characteristics between the different arthritis groups are compared using the chi-square test for categorical variables and multiple range analysis of variance for continuous variables.

RESULTS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. SUBJECTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES

The demographic characteristics of the study sample by OA category are shown in Table 1. Subjects with no formal education and in the not working category had more severe disease. The effect of education is independent of sex, although there were more women with no formal education compared with men. Similarly, those not working had more severe disease independent of sex, although there were more women who were not working. The predominant site of OA involvement was the knees (82%; Table 2). Disease severity was associated with duration of disease, frequency of hospital admissions, use of aids, the total number of analgesic medications taken, and use of social services (Table 3). Many (47%) had tried alternative therapy. The therapeutic side effects were considerable: 42% experienced gastrointestinal side effects as a result of therapy, 28% needed to take gastrointestinal medication for these side effects, and 11% required endoscopy. Some sex differences were noted: women receive medical treatment for a longer duration in the mild disease category and experienced more gastrointestinal discomfort compared with men (Table 3). For those who had undergone joint replacement surgery, the pattern of clinic attendance appeared different between men and women. For men, outpatient clinic attendance was confined to specialist clinics, whereas women continued to attend a government primary care clinic as well as private clinics. In the severe disease category, more women employed domestic helpers compared with men. Those in the severe disease category took more days off work (Table 4). Overall, the disease had a considerable social impact in that it affected family or close relationships in 44% of the subjects, and changes in living arrangement had to be made in 15.5% of the subjects (Table 5). Social impact was related to disease severity.

Table 1. Demographic characteristics of the studied sample by disease severity
 Mild n = 219Severe n = 290Prosthesis n = 65Total n = 574P, χ2
M n (%)F n (%)All n (%)M n (%)F n (%)All n (%)M n (%)F n (%)All n (%)Total n (%)
  • *

    P < 0.05 by chi-square test between men and women within the same category.

  • P < 0.001 by chi-square test between men and women within the same category.

  • P < 0.001 by chi-square test between the 3 groups, same sex.

  • §

    P < 0.01 by chi-square test between men and women within the same category.

  • P < 0.01 by chi-square test between the 3 groups, same sex.

Age group, years           
 <5015 (24.2)24 (15.3)39 (17.8)10 (16.9)27 (11.7)37 (12.8)3 (20.0)4 (8.0)7 (10.8)83 (14.5)0.068
 50–6923 (37.1)70 (44.6)93 (42.5)28 (47.5)76 (32.9)104 (35.9)4 (26.7)19 (38.0)23 (35.4)220 (38.3) 
 70+24 (38.7)63 (40.1)87 (39.7)21 (35.6)128 (55.4)149 (51.4)8 (53.3)27 (54.0)35 (53.8)271 (47.2) 
Sex           
 Male  62 (28.3)  59 (20.3)  15 (23.1)136 (23.7)0.111
 Female  157 (71.7)  231 (79.7)  50 (76.9)438 (76.3) 
Education level           
 No formal14 (22.6)*57 (36.3)71 (32.4)8 (13.6)134 (58.0)142 (49.0)6 (40.0)34 (68.0)40 (61.5)253 (44.1)<0.001
 Primary20 (32.3)56 (35.7)76 (34.7)23 (39.0)58 (25.1)81 (27.9)3 (20.0)10 (20.0)13 (20.0)170 (29.6) 
 Secondary and above28 (45.1)44 (28.0)72 (32.9)28 (47.4)39 (16.9)67 (23.1)6 (40.0)6 (12.0)12 (18.5)151 (26.3) 
Occupation           
 White collar4 (6.4)15 (9.6)19 (8.7)7 (11.9)§9 (3.9)16 (5.5)1 (6.7)0 (0.0)1 (1.5)36 (6.3)<0.001
 Blue collar22 (35.5)18 (17.0)40 (18.3)10 (17.0)20 (8.6)30 (10.4)1 (6.7)1 (2.0)2 (3.1)72 (12.5) 
 Not working36 (58.1)124 (79.0)160 (73.0)42 (71.2)202 (87.4)244 (84.1)13 (86.7)49 (98.0)62 (95.4)466 (81.2) 
Mean annual income HK$1,000           
 Mean ± SD (n)  193.6 ± 221.0 (58)  112.6 ± 76.6 (42)  118.0 ± 65.8 (3)158.3 ± 177.0 (103)0.071
Table 2. Disease characteristics by sex
 Men, n = 136Women, n = 438Total n = 574
Mild n = 62Severe n = 59Prosthesis n = 15Mild n = 157Severe n = 231Prosthesis n = 50
  • *

    P < 0.001 by chi-square test comparing between 3 groups, same sex.

  • P < 0.05, by multiple range test comparing severe group, same sex.

  • P < 0.05 by multiple range test comparing prosthesis group, same sex.

  • §

    P < 0.05 by analysis of variance comparing 3 groups, same sex.

Site of osteoarthritis       
 Hip, n (%)5 (8.1)9 (15.3)2 (13.3)7 (4.5)24 (10.4)11 (22.0)*58 (10.1)
 Knee, n (%)45 (72.6)44 (74.6)13 (86.7)134 (85.4)195 (84.4)41 (82.0)472 (82.2)
Duration of osteoarthritis, years, Mean ± SD6.5 ± 6.939.8 ± 9.5212.5 ± 6.1§10.6 ± 10.2111.1 ± 9.6914.6 ± 8.76§10.6 ± 9.56
Disease severity, n (%)       
 I10 (16.1)0017 (10.8)01 (2.0)28 (4.9)
 II52 (83.9)04 (26.7)140 (89.2)08 (16.0)204 (35.5)
 III051 (86.4)11 (73.3)0206 (89.2)34 (68.0)302 (52.6)
 IV08 (13.6)0025 (10.8)7 (14.0)40 (7.0)
Table 3. Utilization of health and social services (items contributing to direct costs)
 Men, n = 136Women, n = 438Total n = 574
Mild n = 62Severe n = 59Prosthesis n = 15Mild n = 157Severe n = 231Prosthesis n = 50
  • *

    P < 0.05 by multiple range test comparing severe group, same sex.

  • P < 0.05 by multiple range test comparing prosthesis group, same sex.

  • P < 0.05 by t-test comparing sex, same osteoarthritis (OA) group.

  • §

    P < 0.01 by analysis of variance (ANOVA) comparing 3 groups, same sex.

  • P < 0.05 by ANOVA comparing 3 groups, same sex.

  • #

    P < 0.001 by chi-square test comparing 3 groups, same sex.

  • **

    P < 0.05 by chi-square test comparing 3 groups, same sex.

  • ††

    P < 0.05 by chi-square test comparing sex, same OA group.

  • ‡‡

    P < 0.01 by chi-square test comparing 3 groups, same sex.

Years of medical treatment, mean ± SD (n)5.3 ± 6.23* (57)9.4 ± 9.44 (54)11.4 ± 6.89§ (15)8.4 ± 8.20 (147)9.3 ± 7.56 (218)11.1 ± 7.42 (50)8.8 ± 7.89 (541)
Frequency of clinic attendance in the past 12 months, mean ± SD (n)       
 Accident and emergency department1.6 ± 1.34 (5)1.7 ± 1.08 (16)1.5 ± 0.71 (2)1.4 ± 0.52 (8)2.1 ± 1.83 (35)1.8 ± 0.98 (6)1.8 ± 1.45 (72)
 Specialist outpatient clinic3.5 ± 2.86 (37)3.6 ± 2.47 (45)3.6 ± 2.34 (14)2.9 ± 1.57* (107)3.5 ± 2.03 (175)3.7 ± 2.21 (46)3.4 ± 2.1 (424)
 Government primary care clinic2.0 ± 1.08 (13)2.1 ± 1.36 (8) 3.2 ± 1.91 (23)4.9 ± 3.97 (38)4.3 ± 1.53 (3)3.7 ± 3.11 (85)
 Private clinic4.4 ± 3.09 (12)10.9 ± 13.82 (12) 6.9 ± 8.86 (34)7.5 ± 9.45 (67)8.6 ± 12.65 (7)7.5 ± 9.54 (132)
Frequency of hospital admission in the past 12 months       
 HA hospital, n (%)1 (1.6)6 (10.2)††4 (26.7)6 (3.8)24 (10.4)17 (34.0)58 (10.1)
 Duration of hospitalization, days, mean ± SD228.0 ± 26.635.5 ± 21.754.8 ± 3.4336.4 ± 73.9451.7 ± 50.3336.1 ± 56.64
 Private hospital, n (%)00††001 (0.4)01 (0.2)
Total number of investigations, mean ± SD (n)1.9 ± 2.02 (62)2.5 ± 2.49 (59)3.1 ± 1.98 (15)2.4 ± 2.61 (157)2.8 ± 2.85 (231)3.4 ± 2.81 (50)2.6 ± 2.67 (574)
Joint replacement surgery, n (%)       
 Knee  10 (66.7)  34 (68.0)44 (7.7)
 Hip  5 (33.3)  16 (32.0)21 (3.7)
Aids received, n (%)7 (11.3)27 (45.8)††14 (93.3)#27 (17.3)127 (55)47 (94)#249 (43.4)
Home alterations, n (%)5 (8.0)17 (28.9)††3 (20)11 (7)45 (19.4)14 (28)95 (16.5)
No. of physiotherapy sessions in the past 12 months, mean ± SD (%)12.9 ± 17.41 (7)11.7 ± 12.95 (15)36.5 ± 41.72 (2)13.1 ± 23.65 (19)19.6 ± 26.76 (61)37.5 ± 55.03 (15)19.7 ± 30.36 (119)
No. of occupational therapy sessions in the past 12 months, mean ± SD (n)   1 (1)11.0 ± 7.89 (8)41.0 ± 20.69 (4)18.8 ± 18.75 (13)
No. of analgesic medication currently taken, n (%)       
 019 (30.6)9 (15.3)††7 (46.7)**38 (24.2)49 (21.2)18 (36.0)140 (24.4)
 122 (35.5)27 (45.8)††3 (20.0)67 (42.7)82 (35.5)15 (30.0)216 (37.6)
 219 (30.6)18 (30.5)††4 (26.7)47 (29.9)89 (38.5)13 (26.0)190 (33.1)
 ≥32 (3.2)5 (8.5)††1 (6.7)5 (3.2)11 (4.8)4 (8.0)28 (4.9)
No. experiencing side effects from medication, n (%)       
 Gastric discomfort12 (19.4)17 (28.8)††6 (40.0)61 (38.9)100 (43.3)16 (32.0)212 (36.9)
 Gastric ulcer3 (4.8)3 (5.1)††4 (26.7)‡‡6 (3.8)15 (6.5)031 (5.4)
No. requiring medication because of side effects, n (%)11 (17.7)15 (25.4)††5 (33.3)48 (30.6)67 (29.0)15 (30.0)161 (28.0)
No. requiring endoscopy because of side effects, n (%)5 (8.1)3 (5.1)††5 (33.3)‡‡14 (8.9)33 (14.3)5 (10.0)65 (11.3)
No. using alternative therapy, n (%)19 (30.6)24 (40.7)††8 (53.3)73 (46.5)118 (51.1)28 (56.0)270 (47.0)
No. receiving support from social services5 (8.1)19 (32.2)††7 (46.7)#21 (13.4)66 (28.6)20 (40.0)138 (24.0)
No. entering residential care2 (3.2)4 (6.8)††1 (6.7)4 (2.5)17 (7.4)5 (10.0)33 (5.7)
Table 4. Items contributing to indirect costs*
 Men, n = 136Women, n = 438)Total n = 574
Mild n = 62Severe n = 59Prosthesis n = 15Mild n = 157Severe n = 231Prosthesis n = 50
  • *

    OA = osteoarthritis.

  • P < 0.05 by multiple range test comparing severe group, same sex.

  • P < 0.05 by chi-square test comparing sex, same OA group.

  • §

    P < 0.01 by chi-square test comparing 3 groups, same sex.

Days taken sick leave because of OA, mean ± SD (n)5.6 ± 7.68 (13)23.3 ± 28.29 (8) 4.3 ± 3.02 (19)20.8 ± 25.4 (16)30 (1)12.3 ± 19.1 (57)
Friends/relatives need to take leave, n (%)2 (3.2)5 (8.5)011 (7.0)28 (12.1)4 (8.0)50 (8.7)
Family member needs to give up work, n (%)0001 (0.6)7 (3.0)1 (2.0)9 (1.6)
Ever changed job because of OA, n (%)3 (4.8)1 (1.7)1 (6.7)1 (0.6)2 (0.9)08 (1.4)
Quit job because of OA, n (%)08 (13.6)2 (13.3)3 (1.9)10 (4.3)4 (8.0)27 (4.7)
Employ a domestic helper because of OA, n (%)01 (1.7)1 (6.7)4 (2.5)28 (12.1)6 (12.0)§40 (7.0)
Table 5. Social impact of osteoarthritis (OA)
 Men, n = 136Women, n = 438Total n = 574
Mild n = 62Severe n = 59Prosthesis n = 15Mild n = 157Severe n = 231Prosthesis n = 50
  • *

    P < 0.01 by chi-square test comparing 3 groups, same sex.

  • P < 0.001 by chi-square test comparing 3 groups, same sex.

OA affect family or other close relationship, n (%)16 (25.8)32 (54.2)5 (33.3)*49 (31.2)126 (54.5)26 (52.0)254 (44.3)
OA cause changes to living arrangements, n (%)4 (6.5)11 (18.6)3 (20.0)9 (5.7)50 (21.6)12 (24.0)89 (15.5)

The direct costs to the government and patients' out-of-pocket expenses are listed in Table 6. The disease incurred considerable out-of-pocket costs to the patient, ranging from HK $4,860 to $11,180 per annum depending on disease severity, with the highest expenditure in the joint replacement group. The ratio of government cost to out-of-pocket expenditure increased with disease severity, being highest in the joint replacement group. The ratio of direct to indirect costs also increased with disease severity, being highest in the prosthesis group (Table 7). In those who have had hip/knee replacements, the main cost drivers are hospital costs (HK $49,960), outpatient physiotherapy (HK $5,670), and outpatient physician services (HK $3,310) besides the operation (HK $116,380). In addition, those patients also drew disability allowance and Comprehensive Social Security Assistance benefits due to OA (HK $13,880 per person per annum).

Table 6. Direct costs estimated with full sample as denominator*
 Mild conditionSevere conditionProsthesis
  • *

    Data are in Hong Kong dollars (HKD). 1 US dollar = 7.8 HKD. Quartiles are in parentheses. Costs are estimated from the perspective of government unless stated otherwise. Costs are expressed as average cost per patient per annum.

n21929065
Hospital costs, inpatient439 (0;0)11138 (0;0)48,740 (0;32,580)
Hospital costs, inpatient, patient out-of-pocket214 (0;0)950 (0;0)1196 (0;710)
Operation, hip/knee surgery/replacement0 (0;0)0 (0;0)116,380 (60,000;135,000)
Outpatient costs1,045 (195; 1370)1,520 (650;1,950)1,690 (910;2,280)
Outpatient costs, patient out-of-pocket2,840 (37;150)960 (74;190)1,620 (74;220)
Physiotherapy and occupational therapy700 (0;0)2290 (0;910)5,670 (0;910)
Prescription medications, excluding traditional Chinese medicine1,630 (0;2,200)2,080 (250;3,140)2,150 (0;2,830)
Cost of traditional Chinese medicine, patient out-of-pocket507 (0;0)490 (0;160)260 (0;0)
Long-term care, living in old age home1,210 (0;0)1,140 (0;160)1,110 (0;0)
Costs arising from side effects of medication1,110 (0;0)4,180 (0;0)440 (0;0)
Costs arising from side effects of medication, patient out-of-pocket160 (0;0)450 (0;0)0 (0;0)
Total average cost to the government10,12035,700195,630
Total average cost to the patient4,86011,11011,180
Table 7. Direct and indirect cost estimates for different disease categories*
 DirectIndirectRatio of direct to indirect cost
  • *

    Data are average costs per person per year in Hong Kong dollars (HKD). 1 US dollar = 7.8 HKD.

Mild11,6903,3003.5:1
Severe40,1806,6406.1:1
Prosthesis, first year342,04012,25027.9:1
Prosthesis, subsequent year146,6903,64040.3:1

Overall, 8 (1.4%) patients had changed jobs because of OA. The mean value of difference between preceding wage rates and ensuing wage rates for these 8 patients was HK $62,000 (SD $67,400) per annum. Twenty-seven (4.7%) patients quit their jobs due to OA, with mean value of wage loss of HK $80,700 (SD $87,200). Fifty-seven (9.9%) patients needed to take leave from their work to see the doctor. The mean productivity loss due to sick leave was HK $3,900 (SD 6,100). Fifty (8.7%) patients needed relatives or friends to take leave from their work to accompany him/her to see the doctor. Based upon the number of days taken off work and the wage rates reported, the mean productivity loss was evaluated at HK $2,410 (SD $6,030). Nine (1.6%) patients reported that a family member needed to give up work to look after him/her, with mean wage loss of $53,570 (SD $43,300) per annum.

An estimate was made on the total population cost of OA in Hong Kong. Using data on age-adjusted prevalence of knee OA in men and women obtained in a recent door-to-door survey (Lau E et al, unpublished observations), the number of people with OA is estimated to be approximately 200,000. Assuming that 20% of people with OA belong to the severe category and 90% of these seek medical help; 80% of people with OA belong to the mild category and 50% of these seek help; and subjects with joint replacement live for 5 years, the total annual cost is HK $3.5 billion (Table 8). This represents 0.28% of the GNP at current market prices. The 2-way sensitivity analysis, allowing the assumptions on fraction of severity OA and proportion of patients who seek help to vary simultaneously, indicated that the total annual cost ranged from HK $3.2 billion to HK $3.9 billion for various combinations of assumptions.

Table 8. Estimate of cost of OA for the Hong Kong population*
TypeCost/person HKDNo.Year total HKD
  • *

    OA = osteoarthritis; HKD = Hong Kong dollar. One-year total cost (3.5 billion) is 0.28% of the gross national product (HKD 1,258.6 billion).

Prosthesis, first year354,290700248 million
Prosthesis150,3302,800421 million
Severe OA46,82036,0001,685 million
Mild OA14,99080,0001,199 million
All120,0003.5 billion

DISCUSSION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. SUBJECTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES

Musculoskeletal complaints are common among elderly populations, having significant impact on functional ability. In the US, the prevalence of knee pain among the 60–90+ age group was 18% in men and 24% in women, and was associated with difficulties in performing physical functional activities (14). Among Chinese subjects, the prevalence of knee OA in those aged 60 years and over was similar to that for American men, but higher for women (15). In Hong Kong Chinese subjects aged 70 and older, 41% complained of musculoskeletal pain, the knees being the most common joint affected (25–27% in men and 48–50% in women) (3). Musculoskeletal pain was associated with physical and psychological dysfunction. Yet there are few articles of full economic evaluations on musculosketal diseases as a group, and few examine OA separately (16). No economic evaluation of OA had been reported in Chinese populations. Such information would be important in view of the aging population, the relatively high prevalence of the condition, and limited health care resources.

The association between disease severity and socioeconomic status in this study is compatible with observations among whites, where age, being single, unemployment, and low income have been associated with severity of disease (16). In a study of risk factors for OA in Hong Kong Chinese, obesity, joint injury, climbing stairs, and lifting heavy weights frequently were identified as significant risk factors (6). These factors may be more prevalent among those in the lower socioeconomic groups, accounting for the observed association between disease severity and socioeconomic status. The markedly greater involvement of knees compared with hips in this survey is compatible with previous studies showing lower prevalence of hip OA in Asians (17, 18). This difference may result in different economic impact of OA between white and Chinese populations because it is uncertain whether OA involving the knee or hip results in greater functional disability. However, it is likely that if only the knees are involved compared with both hip and knees, the latter would incur greater costs. It is possible that OA may incur greater costs in whites because the prevalence of hip OA is higher than in Chinese, although the prevalence of knee OA is similar.

There are sex differences in the socioeconomic impact of OA in this population. Women received medical treatment for a longer duration compared with men in the mild disease category, and they also experienced more gastrointestinal discomfort. This difference may be a reflection of sex differences in the natural history of OA. The fact that women need to employ domestic help more than men in the severe disease category is probably a reflection of the fact that men in general are supported by women in domestic chores in this society, whereas women are not. This tendency may also explain the finding that men in this survey did not utilize occupational therapy services. This observation is compatible with the observation among Australians, that women spent more on medications and receive more assistance from family and friends, thus incurring greater cost (19). After joint replacement surgery, men appeared to only require specialist outpatient followup and not primary care or private clinic consultations, in marked contrast to women, where the pattern of clinic attendance was similar to those who have not had surgery. It is possible that there are sex differences in the effect of surgery, or that women tend to have arthritis affecting more sites, or that they have a greater number of comorbidities.

Two questions evaluating the social impact of OA used in the Australian study were also used in this survey. Between 25% and 54% of subjects in this survey considered that the disease affected their family or close relationships, compared with 29% in the Australian study (19). Between 6% and 22% of subjects stated that the disease resulted in changes to their living arrangements, compared with 20% of Australians. The social impact appears comparable between Hong Kong Chinese and Australians. However, the 2 groups are not strictly comparable because of probable differences in disease severity profile.

It can be seen that OA incurs considerable direct costs to both government and individuals, increasing with disease severity. For mild OA, the out-of-pocket cost is approximately 50% of the cost paid by the government. However, for severe OA, the government contributes roughly 3 times the amount paid by the individual, with the latter not increasing significantly compared with the mild disease group. With increasing severity of disease, the economic burden is gradually shifted to the government. The costs associated with joint replacement are largely borne by the government. This is a reflection of the virtually free health care system provided by the government, which covers primary to tertiary care, including drugs, investigations, clinic attendance, hospital stays, and operations. Patients pay a nominal fee between HK $40 and $70 to receive these services. For those who are totally reliant on social welfare, the average out-of-pocket expenditure is high, representing approximately 20–50% of their annual income from social security. However, this is probably an overestimate because in the calculation of out-of-pocket expenses, the amount paid to the government's health services is included, and for these subjects, the government's fees are waived. Compared with the direct costs of medical services for OA patients provided by a health maintenance organization, the average cost per patient per year was US $543 (HK $4,235), with similar proportions for hospital care, medication, and ambulatory care (7). Although a direct comparison cannot be made because of different years of evaluation and sample structure (our study recruited roughly equal numbers of patients in different disease categories), the proportions of costs for hospital care, ambulatory care, and medication are similar. In another study in the US, OA subjects incur an average of US $282 (HK $2,200) in indirect and nonmedical costs (20). Differences in the structure, management, and financing of the Hong Kong health care system; differences in method of calculation of loss of productivity (work disability not included in this study); and the long recall period (possibility resulting in underestimation of productivity loss), may account for the difference in the ratio of direct to indirect cost of OA and the total cost to the government as a percentage of the GNP. In the US, Canada, UK, France, and Australia, indirect costs exceed direct costs, and the total cost varies from 1% to 2.5% of the GNP (8). In Hong Kong, direct costs far exceed indirect costs, and the total costs represent only 0.28% of the GNP at current prices.

It is interesting to note that the costs incurred from the side effects of medication is similar to the cost of prescription medication, and in the severe OA category, actually exceeds the cost of medication. The problem of side effects of NSAIDs, which are commonly used for OA in Hong Kong, had been documented in this population previously (4, 5). The use of cyclooxygenase 2 (COX-2) inhibitors may have a role in reducing the cost of the disease. A recent Swedish study evaluating the economic and health impact of the introduction of celecoxib for the treatment of OA and rheumatoid arthritis concluded that its use could improve health care at reduced costs (21). A Canadian study concluded that for those aged ≥65 years, the incremental cost of using COX-2 inhibitors in place of current treatment alternatives would not impose an excessive incremental impact on a Canadian provincial health care budget (22).

Joint replacement surgery has been shown to reduce out-of-pocket costs to patients with OA, and improve their quality of life (23, 24), although the improvement is greater in patients with hip compared with knee replacement. Our finding shows that the costs for patients with joint replacement are not lower than for the mild or the severe disease category. Various factors may account for this finding. Patients still attend orthopedic outpatient clinics regularly after surgery; there may be other joints involved; and rehabilitation may not be optimal.

There are limitations to this study. The retrospective design may result in inaccuracies in the information, particularly because the majority of the subjects belong to the older age group and the recall period is long—12 months or more. The numbers of radiographic examinations, physician visits, or days off work may not be exact. However, whenever possible, the data is cross-checked with the patient records. In Hong Kong, there are multiple health care providers in the government or private sectors, and patients often consult more than 1 provider simultaneously. This represents a logistic problem in cross-checking consultation episodes. There is no central patient-held medical record. The diagnosis of OA is from medical records, and not made by a rheumatologist or orthopedic surgeon in all cases, the milder category being cared for in the primary care setting. This might result in overdiagnosis in the mild disease category. On the other hand, OA is a relatively common condition among older patients who have many comorbidities, which tend to receive more attention, and this may result in under recruitment to the study, affecting the profile of use of health service. Although the interviewer recorded use of services as a result of arthritis only, the existence of comorbidities will indirectly affect our evaluation. For example, a patient with OA and chronic lung disease may require a longer period of rehabilitation after joint replacement surgery. It would not be practical to exclude subjects with comorbidities becuase a large number of elderly subjects would be excluded from the economic evaluation. In spite of these limitations, the study included enough numbers to allow evaluations in different disease severity groups, examination of sex differences, a broad recruitment base from primary to tertiary settings, and an estimate of out-of-pocket expenses in addition to costs to the government.

As in Western countries, socioeconomic impact to OA patients is similar. However, direct costs are much higher than indirect costs in Hong Kong, and the total government expenditure as a percentage of the GNP is lower, compared with available data from Western countries. This pattern may well change in the future with falling economic productivity and the introduction of a new health care financing system that will increase individual out-of-pocket health expenditure.

REFERENCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. SUBJECTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES
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