Information about the economic impact of illness has become central to health policy debates, affecting the allocation of research funding among conditions and the choice of therapies for specific conditions. Because of the growing importance of cost of illness studies in health policy, the literature concerning the cost of all forms of musculoskeletal conditions for the US as a whole (1–8) and for other nations (9–13), as well as the cost of specific musculoskeletal conditions, including various forms of arthritis and other rheumatic conditions (AORC) (14–37), has been expanding rapidly.
In general, the studies of the economic impact of all forms of musculoskeletal conditions have been derived from population-based surveys, but not directly observed individual-level medical care expenditures or employment status and earnings. In contrast, studies that have tracked the actual costs or expenditures for individuals have used clinical-based samples and are, thus, not representative of the general population. In the present study, we used the results of the Medical Expenditures Panel Survey (MEPS), which melds the methods of the 2 kinds of studies by using a population-based sampling frame and then prospectively tracking actual expenditures and employment and earnings among respondents.
The specific goals of the study were as follows: 1) to provide estimates of all medical care expenditures on behalf of all persons with any form of AORC in the US in 1997, estimates of the increment in expenditures that was specifically attributable to the AORC among persons ages 18 years and older, and estimates of the fraction of total medical care expenditures attributable to the AORC and 2) to provide estimates of lost earnings among persons with AORC ages 18–64 years and estimates of the increment in lost earnings attributable to the AORC among persons of these ages.
A method developed by the investigators in an earlier study concerning all forms of musculoskeletal disease (7) was used to estimate the increment in medical care expenditures attributable to AORC. An expansion of that method was used to estimate the increment in earnings losses.
SUBJECTS AND METHODS
Data from the MEPS, a joint endeavor of the Agency for Healthcare Research and Quality and the National Center for Health Statistics, was used in the present study. MEPS is designed to provide data on health care use, medical care expenditures, sources of payment, and insurance coverage for a representative sample of the civilian noninstitutionalized population of all ages in the US. MEPS also tracks the employment status and earnings of that sample.
The full MEPS data include survey responses from this sample of households (MEPS-H), information from their providers about their medical conditions, information from their healthcare plans about the specifics of these plans, and a separate sample of nursing home residents (38). The MEPS-H sample is derived from the previous year's National Health Interview Survey respondents, who are, in turn, derived from a clustered, random sample of the civilian noninstitutionalized population, with an oversample of African Americans and Hispanics. Data for nursing home residents were not included in the analyses. In the present study, we used data from the 1997 MEPS-H, which included 14,147 households with 34,551 persons (39).
MEPS-H data are collected through 6 rounds of interviews over a 2.5-year period. The first 3 interviews, which cover expenditures, employment, and earnings over an entire year, provided the data used in this analysis. The interviews are used to collect information on health and functional status, health care utilization and expenditures, employment and earnings, as well as basic demographic information. The health status section elicits data on the specific medical conditions each respondent has. The information from the self-report of the respondents is then used to code conditions to 3-digit levels using the International Classification of Diseases, Ninth Revision (ICD-9) system. The utilization and expenditures and the employment and earnings sections elicit information about the previous 4 months in order to improve the reliability of responses.
In the MEPS, expenditure data derive from a combination of the MEPS-H interviews and information obtained from providers. Expenditures in MEPS are defined as the actual expenditures for the medical care services used, regardless of the source of payment (38–40). In contrast to studies of the costs of illness in which costs are tabulated even if uncompensated care is provided, on the assumption that resources are being consumed regardless of payment, in studies of medical care expenditures, the analyst is studying the actual exchange of money. Because MEPS is based on expenditures rather than costs, there are health care encounters enumerated in the survey for which no expenditures were made.
In an entirely fee-for-service system, one could track all expenditures among respondents. However, in many forms of managed care, charges are not rendered when services are provided and, hence, there are no expenditures specific to the medical care encounters. Accordingly, in such instances, MEPS-H imputes expenditures based on the charges incurred within the fee-for-service sector for similar services provided to similar individuals.
We first partitioned the 1997 MEPS-H data into the following chronic condition groups, based on ICD-9 codes: persons with only AORC (ICD-9 codes 274, 354, 390, 391, 443, 446, 710–716, 719–721, and 725–729), persons with both AORC and non-AORC chronic conditions, persons with 1 non-AORC condition, persons with ≥2 non-AORC chronic conditions, and persons with no chronic conditions. The definition of AORC is based on a standard developed by the National Arthritis Data Workgroup (6). Because MEPS-H data used only 3-digit ICD-9 codes, we could only use the Workgroup's 3-digit ICD-9 codes. For a few Workgroup ICD-9 codes for which the presence of a fourth digit is normally necessary, we used the corresponding 3-digit ICD-9 code if we thought it would be composed primarily of the Workgroup's targeted condition. Chronic conditions in general are defined by the protocol devised by Hoffman et al (41), which was designed to provide a conservative estimate of prevalence. Of all 34,551 MEPS respondents, 4,776 met the criteria for any form of AORC.
Because MEPS-H is based on a 2-stage cluster sample rather than a simple random sample of the noninstitutionalized population, it is necessary to weight the data to make inferences for the US population. In MEPS-H, the sampling weights also take into account nonresponse in the households targeted for inclusion and attrition among respondents after completion of the first interview (42). We used SUDAAN software to account for the cluster sampling design in all analyses requiring the calculation of the standard error of estimates (43).
Description of expenditures
We began by enumerating medical care expenditures on behalf of persons of all ages by condition group and by category of health services, as well as the distribution of total health care expenditures. In the foregoing analysis, we tabulated all expenditures among persons in the condition groups, regardless of whether the condition in question accounted for the expenditures. In the tables for these analyses, we indicate the estimates that had low statistical reliability, that is, a relative standard error >30%.
Analysis of increment in health care expenditures
In order to assess the incremental contribution of AORC to health care expenditures, we estimated a series of regressions separately for adults with and without AORC. We then simulated the expected level of expenditures for the AORC group as if they did not have the AORC by applying the parameter estimates derived from the group without the condition to the data for the group with the condition. The increment was then calculated as the difference between these 2 values (44).
To make these calculations with respect to expenditures for ambulatory care, inpatient care, prescription drugs, and residual expenditures, we followed the 2-stage method outlined by Duan et al (45). This method accounts for the distribution of health expenditures in which many persons have no health expenditures or relatively low expenditures, while a small proportion has very high expenditures. In this method, one first uses a logistic regression to estimate the probability that an individual has any expenditures and then uses ordinary least-squares regression on the logarithm of the expenditure to estimate the level of expenditures among those with strictly positive expenditures.
We estimated the incremental contribution of AORC to total expenditures by a 4-stage model, which has also been described by Duan et al (45). The first stage uses a logistic regression to predict the probability of any medical expenditures. The second stage uses a separate logistic regression to predict the probability of any hospital expenditures given the presence of medical expenditures. The third stage uses an ordinary least-squares regression to predict the logarithm of the level of total costs among persons without hospitalizations, and the fourth stage uses ordinary least-squares regression to predict the logarithm of total costs among persons with hospitalizations. Total expenditures include ambulatory and inpatient care, prescription drugs, and a residual category that comprises home healthcare, vision aids, dental visits, and medical devices.
For both the 2-stage and 4-stage models, the log transformation is used in the ordinary least-squares regressions to account for the skewed distribution of expenditures. The resulting estimate, when transformed back to the original units by exponentiation, is biased downward (that is, the expected value of the estimate is lower than the expected value of the population mean). Duan (46) has shown that a simple adjustment called the smearing estimate can be used to adjust for this bias. The smearing coefficient is the mean of the exponentiated residuals from the regression on the log-transformed variable.
All the regression models included independent variables for the presence or absence of AORC and the following 9 other high-cost chronic conditions: hypertension, other forms of heart disease, pulmonary disease, stroke, other neurologic conditions, diabetes, cancer, mental illness, and musculoskeletal conditions other than AORC.
In addition to the indicator variables for conditions, we included variables for age categories (45–64 years and ≥65 years, with 18–44 years as the reference category), sex (female versus male), race (white versus nonwhite), ethnicity (Hispanic versus non-Hispanic), marital status (single, widowed, separated, and divorced, with currently married as the reference category), level of formal education (high school graduate, some college, college graduate, and some graduate school, with less than high school as the reference category), and health insurance status (only public insurance or no insurance, with those having any private insurance as the reference category).
For the 2-stage model, the final estimated expenditure for each individual was obtained by exponentiating the predicted logarithm of expenditures, multiplying that value by the smearing coefficient, and multiplying that, in turn, by the predicted probability of a positive expenditure from the logistic regression. The calculations for the 4-stage model were similar. All of these analyses were limited to the 22,376 MEPS respondents who were 18 years of age or older and who had complete data for all covariates used in the multistage models, of whom 4,457 met the study criteria for any form of AORC.
Calculation of attributable fractions
Attributable fractions, which are the proportion of all health care expenditures in the entire population that would not occur if no one had AORC, were calculated by dividing the increment in total medical care expenditures attributable to AORC by the total medical care expenditures for the entire population. We cross-validated the estimates of attributable fractions in each of 12 cells defined by age and sex. In the cross-validation studies, we estimated 10 different values for the attributable fraction within each cell. We estimated the models on nine-tenths of the data and used that model to calculate the attributable fraction in the other one-tenth of the data. The largest range of estimates within a cell was 8 percentage points, but in most of the cells, the range was ≤3 percentage points.
Estimation of employment and earnings losses
The estimations of earnings losses were limited to persons ages 18–64 years with a history of ever being employed as recorded in MEPS. Earnings losses were estimated only for persons who were ages 18–64 years, both for the substantive reason that labor force participation rates decline precipitously at age 65 years, as individuals reach the earliest age of eligibility for full Social Security retirement benefits, and for the methodologic reason that estimates among persons ages ≥65 years, based on a relatively small sample size, would not be reliable.
To estimate earnings losses, we tabulated the actual employment status of persons with and without AORC who were between the ages of 18 years and 64 years, and, among those who were employed, the hours of work. The absolute level of lost wages was then calculated as the sum of 2 products. The first product was the cost of lost wages among those who were not working at all. This product is equal to the difference in the employment rates of persons with and without AORC times the number of persons with AORC times the mean wage among all employed persons with AORC. The second product was the cost of lost wages among those who continued to work. This product is equal to the difference in the hours of work per year by employed persons with and without AORC divided by the mean hours of work of all persons (yielding the percentage reduction in hours) times the number of persons with AORC times the mean wage among all employed persons with such conditions.
Analysis of increment in earnings losses
We then estimated the increment of earnings losses in a manner analogous to the estimate of the increment in expenditures. Specifically, we began by estimating separate logistic regressions of the probability of employment among persons with and without AORC and then estimated separate ordinary least-squares regressions of the level of annual earnings among the members of the 2 groups with earnings. The regressions included the following independent variables: age (35–44 years, 45–54 years, and 55–64 years, with 18–34 years as a reference), sex, race (white versus nonwhite), ethnicity (Hispanic versus non-Hispanic), marital status (single, widowed, separated, and divorced, with married as the reference category), education level (high school graduate, some college, college graduate, and some graduate school, with less than high school as the reference category), and indicator variables for the same comorbid conditions as described in the direct cost analyses above.
After the regressions were completed, we applied the parameter estimates derived from regressions on persons without AORC to the data from those with such conditions to simulate the expected level of earnings among such persons if they did not have AORC. The increment in earnings losses was then calculated as the difference between the AORC values and simulated non-AORC values. In the ordinary least-squares regressions, the natural logarithm of earnings was used; the results were then transformed back to absolute dollar amounts using separate smearing estimates calculated among persons with and without AORC in a manner analogous to the estimations of medical care expenditures described above.
In order to assess the extent to which estimates of the prevalence and economic impact of AORC were sensitive to the inclusion of potentially problematic ICD-9 codes within the AORC rubric, we eliminated the following ICD-9 codes from the rubric: codes 354 (mononeuritis of the upper extremity; 85% of 255 sample cases were carpal tunnel syndrome in later analyses), 390 and 391 (acute rheumatic fever), and 443 (other peripheral vascular disease; 39% of 25 sample cases were Raynaud's syndrome in later analyses). The elimination of these conditions from the AORC rubric reduced the prevalence of AORC by 3.1% (from 38.4 to 37.2 million) and reduced aggregate medical expenditures by 2.4% (from $186.9 billion to $182.4 billion), while increasing the average expenditure level by 0.8% (from $4,865 to $4,902). Because the results were relatively insensitive to the elimination of these codes and because relying on the definition of AORC from the National Arthritis Data Workgroup uses a standard that permits comparison with other studies (6, 47), we report below the estimates based only on that definition.
We also calculated the sensitivity of the estimate of the increment in direct costs to the inclusion of different forms of several of the independent variables, including age (inclusion of age and age-squared), education (truncation of education at “college graduate”), and comorbidity (inclusion of count of all chronic conditions, rather than disease-specific indicator variables). In no instance did the estimate of the increment in direct costs vary by more than 7.1%. In a similar manner, we calculated the sensitivity of the estimate of the increment in direct costs to the form of the comorbidity variable. Replacement of the chronic condition indicator variables with the count of chronic conditions increased the estimate of the increment in indirect costs by 14.6%.
Medical care expenditures.
Distribution of conditions.
In 1997, 38.423 million persons (14.2% of the civilian noninstitutionalized population) reported any form of AORC. Of those, 32.788 million (12.1% of the entire population and 85.3% of all persons with AORC) also reported having 1 or more non-AORC conditions (Table 1). In that same year, 131.749 million persons (48.6%) reported non-AORC conditions in the absence of AORC and another 101.106 million (37.3%) reported no chronic conditions whatsoever (all told, there were 232.855 million persons without AORC in 1997).
Table 1. Noninstitutionalized population of all ages, by arthritic condition status, US, 1997
|All arthritic conditions||38.423||14.2||100.0|
| Arthritic conditions only||5.635||2.1||14.7|
| Arthritic and nonarthritic conditions||32.788||12.1||85.3|
|All nonarthritic conditions||131.749||48.6|| |
| 1 nonarthritic condition only||58.609||21.6|| |
| ≥2 nonarthritic conditions||73.14||27.0|| |
|No chronic/comorbid conditions||101.106||37.3|| |
A higher proportion of persons with AORC than without AORC were women and white, while a slightly smaller percentage were of Hispanic origin. Such persons were also >2 decades older on average, and reflecting this, they were more likely to be widowed, separated, or divorced and less likely to never have been married (data on characteristics of persons with and without AORC not presented in tables).
Distribution of expenditures.
The 38.423 million persons with any form of AORC had average total medical care expenditures in 1997 of $4,865 ($1,074 among the 5.635 million without non-AORC, $5,516 among the 32.788 million with such conditions). This is much higher than the average of $2,397 among persons with non-AORC conditions or than the $500 among those without chronic conditions (Table 2). The 3 largest components were inpatient costs (39%), ambulatory care (29%), and prescription drugs (14%).
Table 2. Health care expenditures (by type) of the noninstitutionalized population of all ages, by arthritic condition status, US, 1997
|Arthritic conditions||967 (20)||428 (9)||1,394 (29)||103 (2)||1,905 (39)||398 (8)||687 (14)||377 (8)||4,865|
| Arthritic conditions only||290 (27)||123 (11)||413 (38)||35 (3)||320 (30)**||15 (1)**||81 (8)||210 (20)||1,074|
| Arthritic and nonarthritic conditions||1,083 (20)||480 (9)||1,563 (28)||115 (2)||2,177 (39)||464 (8)||792 (14)||406 (7)||5,516|
|Nonarthritic conditions||488 (20)||198 (8)||687 (29)||82 (3)||951 (40)||99 (4)||330 (14)||248 (10)||2,397|
| 1 nonarthritic condition||269 (24)||96 (8)||365 (32)||59 (5)||379 (33)||29 (3)||121 (11)||188 (16)||1,142|
| ≥2 arthritic conditions||664 (20)||280 (8)||944 (28)||101 (3)||1,409 (41)||155 (5)||498 (15)||296 (9)||3,403|
|No chronic conditions||115 (23)||36 (7)||151 (30)||30 (6)||149 (30)||9 (2)**||23 (5)||137 (27)||500|
|All Persons||417 (20)||170 (8)||587 (29)||66 (3)||787 (39)||108 (5)||266 (13)||225 (11)||2,039|
Overall, in 1997, persons with any form of AORC accounted for $186.9 billion in expenditures, the equivalent of ∼2.3% of the gross domestic product for the US in that year, with all but $6.1 billion accounted for by persons reporting AORC as well as non-AORC (Table 3). The 38.423 million persons with any form of AORC represent 14.2% of the US population but account for 34% of all medical care expenditures in the MEPS.
Table 3. Distribution of total health expenditures of the noninstitutionalized population of all ages, by arthritic condition status, US, 1997
|Arthritic conditions||0||60||575||1,644||4,306||20,041||191,297||4,865||186.9 (34)|
| Arthritic conditions only||0||0||98||349||910||3,703||65,316||1,074||6.1 (1)|
| Arthritic and nonmusculoskeletal conditions||0||154||799||2,004||5,114||22,332||191,297||5,516||180.9 (33)|
|Nonarthritic conditions||0||0||223||635||1,847||9,644||351,156||2,397||315.8 (57)|
| 1 nonarthritic condition||0||0||108||337||854||4,494||337,262||1,142||66.9 (12)|
| ≥2 arthritic conditions||0||78||424||1,068||2,870||13,735||351,156||3,403||248.9 (45)|
|No chronic conditions||0||0||0||89||319||1,958||136,109||500||50.5 (9)|
|All persons||0||0||83||394||1,415||8,478||351,156||2,039||553.2 (100)|
Increment in expenditures and attributable fractions.
The $186.9 billion in expenditures among persons with AORC are only partially attributable to the AORC; a significant proportion is due to the other chronic conditions such persons have, as well as to their acute care and wellness care. In Table 4, we present the results of our analysis of the proportion of various kinds of expenditures attributable to AORC among persons ages ≥18 years. Overall, we estimated that all adults with AORC had an increment in total expenditures of $1,391 per person beyond what would be expected of similar persons without such conditions. This is equivalent to a population attributable fraction of 10%, meaning that eliminating AORC would reduce total health care expenditures by 10%. The attributable fraction rose with age, from 6% among persons ages 18–44 years, to 12% among those ages 45–64 years, and to 18% among those ages ≥65 years, as befits a set of conditions associated with aging.
Table 4. Increment in expenditures and attributable fractions for arthritic conditions for the US population ages ≥18 years, 1997, by age and sex group and by expenditure type
|Both sexes|| || || || || || || || || || || || || || || || || || || |
| All ages||22,435||4,449||196,329||36,759||598||768||15||401||1,042||7||112||456||5||176||418||8||1,391||2,689||10|
| 18–44 years||12,199||1,193||108,997||10,674||453||668||7||407||895||4||86||295||3||149||350||4||1,467||2,238||6|
| 45–64 years||6,455||1,717||54,515||13,458||698||812||21||195||930||5||190||483||10||185||467||10||1,377||2,728||12|
| ≥65 years||3,781||1,539||32,817||12,628||627||867||28||605||1,241||19||85||567||6||177||498||14||1,539||3,209||18|
|Females|| || || || || || || || || || || || || || || || || || || |
| All ages||12,187||2,783||102,026||21,862||649||882||16||150||1,045||3||107||522||4||181||444||9||1,163||2,886||9|
| 18–44 years||6,482||722||55,063||6,075||491||771||7||196||902||2||86||341||3||154||373||5||1,268||2,405||6|
| 45–64 years||3,464||1,044||28,207||7,813||757||932||23||−22||942||−1||194||557||10||192||496||11||1,182||2,949||11|
| ≥65 years||2,241||1,017||18,756||7,973||680||993||29||310||1,248||11||74||654||5||182||530||15||1,278||3,456||16|
|Males|| || || || || || || || || || || || || || || || || || || |
| All ages||10,248||1,666||94,303||14,897||514||629||13||795||1,050||12||121||369||5||165||387||7||1,762||2,465||11|
| 18–44 years||5,717||471||53,934||4,599||391||543||6||734||899||7||87||236||3||140||323||4||1,788||2,051||7|
| 45–64 years||2,991||673||26,308||5,644||599||665||19||535||927||12||186||388||10||172||433||9||1,695||2,474||15|
| ≥65 years||1,540||522||14,062||4,654||539||715||25||1,066||1,248||28||108||456||8||168||462||12||1,962||2,931||22|
The attributable fraction associated with AORC was larger for men of all ages (11%) than for women of all ages (9%). The attributable fraction among men ages ≥65 years was particularly pronounced (22%), suggesting that the presence of AORC among men of these ages adds dramatically to their overall medical care expenditures.
Among all persons with AORC, the attributable fraction associated with this group of conditions was highest for outpatient services (15%) and lowest for prescription medications (5%). The attributable fractions associated with inpatient services and the residual category were 7% and 8%, respectively.
Although the attributable fraction for inpatient services was only 7% overall, it was much higher for men, regardless of age (12%), particularly men who were ≥65 years old (28%). Presumably, the relatively high attributable fraction among men these ages reflects the growing prevalence of total joint replacement surgery.
Another way to visualize the magnitude of the costs attributable to AORC is by estimating the aggregate impact of the mean increment in expenditures. Thus, the average increment of $1,391 among each of the 36.759 million persons ages ≥18 years with AORC aggregated to $51.1 billion, or ∼0.6% of the gross domestic product for 1997.
As a result of their markedly lower employment rates (91.0% versus 79.6%; difference 11.4%), ∼2.5 million persons with AORC who were not then employed would have been working if they had had the same employment rate as persons without such conditions (Table 5). However, after controlling for differences in demographic characteristics and comorbidity between the 2 groups, the incremental employment gap was 4.0%, or ∼0.9 million persons.
Table 5. Individual and aggregate employment rates of persons with arthritic conditions ages 18–64 years, raw differences and increments attributable to the arthritic conditions, US, 1997
|Employment rate of persons without arthritic conditions, raw, %||91.0|
|Employment rate of persons with arthritic conditions, raw, %||79.6|
|Individual employment rate gap, raw, %||11.4|
|Aggregate employment gap, raw, no. of persons*||2,542,603|
|Individual incremental employment rate gap attributable to arthritic conditions, %||4.0|
|Aggregate incremental employment gap attributable to arthritic conditions, no. of persons*||889,948|
The raw wage loss costs associated with the forgone earnings of the ∼2.5 million persons with AORC who would have been working but were not was $73.2 billion ($3,293 per working-age person) (Table 6). The wage losses of the then currently employed persons with AORC that were associated with their lower earnings as compared with persons without such conditions was $9.2 billion ($519 per working-age person with AORC), leaving an overall net loss associated with AORC of $82.4 billion ($3,812 per working-age person with AORC). After controlling for demographic characteristics and comorbidity, the increment in the net individual earnings gap attributable to AORC averaged $1,579, for a total of $35.1 billion.
Table 6. Individual and aggregate earnings losses of persons with arthritic conditions ages 18–64 years, raw differences and increments attributable to the arthritic conditions, US, 1997
|Aggregate lost earnings due to lower employment rates among persons with arthritic conditions, raw, billions||73.2|
|Per capita earnings gap due to lower employment rates among persons with arthritic conditions, raw||3,293|
|Aggregate lost earnings among employed persons with arthritic conditions, raw, billions||9.2|
|Per capita lost earnings among employed persons with arthritic conditions, raw||519|
|Net aggregate earnings gap, raw, billions||82.4|
|Net per capita earnings gap, raw||3,812|
|Aggregate incremental net earnings gap attributable to arthritic conditions, billions||35.1|
|Per capita incremental net earnings gap attributable to arthritic conditions||1,579|
Demographic factors associated with employment status.
Because almost all of the earnings losses associated with AORC occurred among those who were not working, stopping work loss is essential to containing the earnings losses associated with this group of conditions. Table 7 shows the demographic factors associated with employment status among persons ages 18–64 years with AORC and a work history. The characteristics associated with a significantly reduced odds of employment included female sex (odds ratio 0.58; 95% confidence interval 0.44–0.75) and increments of age, while increasing increments of education and being white were associated with an increased odds of employment.
Table 7. Factors associated with employment of persons with arthritic conditions ages 18–64 years, controlling for demographic characteristics and 9 comorbid conditions, US, 1997
|Age|| || |
| 18–34 years||Reference|| |
| 35–44 years||0.55||0.33–0.94|
| 45–54 years||0.37||0.22–0.64|
| 55–64 years||0.12||0.07–0.20|
|Race|| || |
| Nonwhite||Reference|| |
|Ethnicity|| || |
| Non-Hispanic||Reference|| |
|Education|| || |
| Less than high school||Reference|| |
| High school graduate||1.9||1.41–2.56|
| Some college||2.85||1.94–4.18|
| College graduate||3.72||2.29–6.04|
| Some graduate school||5.5||3.09–9.82|
|Marital status|| || |
| Married||Reference|| |
| Widowed, separated, divorced||1.05||0.79–1.39|
| Never married||1.07||0.66–1.72|
We performed 2 kinds of estimates of both the medical care expenditures and earnings losses associated with arthritis and other rheumatic conditions. In the first estimate of medical care expenditures, we recorded the magnitude and distribution of all medical care expenditures among the 38.423 million persons with AORC, and we found that such persons experienced mean total expenditures of $4,865, or $186.9 billion overall. Hospital admissions accounted for 39% of these expenditures; ambulatory care (29%) and prescription drugs (14%) were the next 2 largest components. Although average expenditures of $4,865 among persons with AORC were substantial, most individuals avoided such high levels of expenditures. Among persons with AORC alone, the average expenditures were only $1,074 and, even at the 95th percentile, were relatively small ($3,703). Among persons with both AORC and non-AORC chronic conditions, median expenditures were only $2,004 and only rose to $5,114 at the 75th percentile.
Nevertheless, expenditures incurred on behalf of persons with AORC represent a substantial drain on the nation's economy. In 1995, the National Arthritis Data Workgroup reported that both direct and indirect costs of all forms of musculoskeletal conditions, including AORC, for 1988 was 2.5% of the gross national product of the US (6). In the present study, however, we found that total medical expenditures for AORC alone in 1997 were equivalent to ∼2.3% of the gross domestic product for that year (48), and would suggest that both the accounting methods used in the MEPS and the aging of the population may have contributed to the increase in the estimated impact of these conditions.
In the second set of analyses of medical care expenditures, we estimated the proportion of total expenditures attributable to AORC among persons ages ≥18 years. Overall, AORC was associated with an attributable fraction of 10% for medical expenditures, or $1,391 per person with AORC, which aggregates to $51.1 billion, the equivalent of about 0.6% of the gross domestic product in 1997. Since in a recession, by definition, the economy retrenches by ≥1% of the gross domestic product for at least 2 consecutive quarters, the increment in medical care expenditures attributable to AORC has an impact slightly less than that of a small recession, but unlike a recession, it occurs in perpetuity.
In the unadjusted analysis, persons with AORC ages 18–64 years who were not working were estimated to be responsible for $73.2 billion in earnings losses, while those who were employed were responsible for losses of $9.2 billion, resulting in an estimate of net earnings losses of $82.4 billion. The finding that those who were not employed were responsible for the bulk of the lost income is consistent with clinical studies in specific rheumatic conditions that have shown a total loss of employment to be more common than a reduction in hours or a change in work activities (49). After controlling for demographic characteristics and comorbidity, the incremental value of the aggregate net earnings gap attributable to AORC was ∼$35.1 billion, or $1,579 per person with AORC ages 18–64 years.
In a recent estimate of the economic burden of musculoskeletal conditions, Rice and colleagues (1) calculated that the direct costs of AORC in 1995 were $21.7 billion, or about $22.8 billion in 1997 dollars. In the present study, we estimated that the increment in medical care expenditures attributable to AORC was $51.1 billion in 1997 dollars. Thus, the direct accounting of medical care expenditures made possible by the development of the MEPS may have resulted in a substantial increase in the estimate of the direct costs attributable to AORC. In the same study by Rice, it was estimated that the indirect costs of AORC among persons ages 18–64 years were $60.8 billion in 1995, or about $64.0 billion in 1997 dollars. Thus, the estimate of the earnings losses attributable to AORC in the current study ($35.1 billion) is considerably smaller than the estimate made by Rice and colleagues. The ability to control for differences in characteristics other than the AORC between persons with and without AORC may account for the lower estimate in the present study. The estimate of earnings losses, however, is within the range of estimates reported by Dunlop and colleagues (8).
Some AORC conditions were excluded from the analysis because 4-digit ICD-9 data that would identify these conditions were not available. This underestimation of cost was likely balanced by the presence of some non-AORC conditions that were included in the analysis because 3-digit ICD-9 codes are less specific.
There are 4 reasons why medical care expenditures may have been underestimated in this study. First, the study sample was limited to the US civilian noninstitutionalized population and, thus, expenditures by institutionalized and military populations were not included. Second, the MEPS measures only medical expenditures and does not capture services for which there is no exchange of money. Third, we did not include in this analysis expenditures for complementary and alternative medicine, which is becoming an increasingly common treatment modality, especially among individuals with AORC (50, 51). Fourth, the data from the current study precede the introduction of biologics for the treatment of rheumatoid arthritis, more-aggressive testing for the presence and treatment of osteoporosis, and the growth of the coxibs and/or the use of proton-pump inhibitors with traditional nonsteroidal antiinflammatory drugs. However, it should be pointed out that the relatively low prevalence of RA means that the introduction of biologics would add, at most, several billion dollars to the estimate of the aggregate increment of ∼$51 billion that was attributable to all forms of AORC. Moreover, although it is becoming increasingly common to prescribe bone densitometry for women at risk of developing osteoporosis, the added costs of such testing would be balanced by the reduction in the number of women receiving estrogen replacement therapy. Nevertheless, all of these developments have undoubtedly increased the incremental costs associated with AORC since 1997, making the estimates of the present study relatively conservative.
There are some limitations that would apply to the estimates of the increment in direct and indirect costs. The MEPS survey provides no information with which to estimate whether persons with AORC differ from the rest of the population in their level of perseverance in the face of medical symptoms with respect to the kinds of medical care services procured or their willingness to stay at work.
These 1997 cost estimates, and the 1996 expenditures presented by Dunlop et al (8), are the first national population–based AORC cost estimates based on directly observed individual-level expenditure and employment data. This study is the first to provide attributable fractions for medical care expenditures due to AORC. These expenditure estimates are an essential component of the ongoing effort by the Centers for Disease Control and Prevention to characterize the burden of AORC in the US for a single year, 1997. Thus far, the impact of AORC on hospitals (52) and ambulatory care (47, 53) has been reported, and these data will soon extend to characterizing the burden of AORC in nursing homes and assessing mortality rates among persons with AORC.
The results reported here indicate that a larger proportion of the indirect costs (41% of all $82.4 billion in indirect costs, or $35.1 billion) than of the direct costs (29% of all $186.9 billion, or $51.5 billion) of AORC is attributable to the AORC. This finding from a population-based study of persons with all forms of AORC is consistent with studies of persons with discrete rheumatic conditions (19) and indicates that the prevention of work loss and the resultant earnings losses should be central to public health policy aimed at reducing the impact of AORC, even as the cost of medical care continues to garner a disproportionate amount of the public's attention.