SPINE Volume 29, Number 1, pp 79–86 ©2003, Lippincott Williams & Wilkins, Inc. Estimates and Patterns of Direct Health Care Expenditures Among Individuals With Back Pain in the United States Xuemei Luo, PhD,*† Ricardo Pietrobon, MD,† Shawn X Sun, PhD,‡ Gordon G. Liu, PhD,‡ and Lloyd Hey, MD, MS*† Study Design. Secondary analysis of the 1998 Medical Expenditure Panel Survey. Objective. To estimate total health care expenditures incurred by individuals with back pain in the United States, calculate the incremental expenditures attributable to back pain among these individuals, and describe health care expenditure patterns of individuals with back pain. Summary of Background Data. There is a lack of updated information on health care expenditures and expenditure patterns for individuals with back pain in the United States. Methods. This study used data from the 1998 Medical Expenditure Panel Survey, a national survey on health care utilization and expenditures. Total health care expenditures and per-capita expenditures among individuals with back pain were calculated. Multivariate regression models were used to estimate the incremental expenditures attributable to back pain. The expenditure patterns were examined by stratifying individuals with back pain by sociodemographic characteristics and medical diagnosis, and calculating per-capita expenditures for each stratum. Results. In 1998, total health care expenditures incurred by individuals with back pain in the United States reached $90.7 billion and total incremental expenditures attributable to back pain among these persons were approximately $26.3 billion. On average, individuals with back pain incurred health care expenditures about 60% higher than individuals without back pain ($3,498 vs. $2,178). Among back pain individuals, at least 75% of service expenditures were attributed to those with top 25% expenditure, and per-capita expenditures were generally higher for those who were older, female, white, medically insured, or suffered from disc disorders. Conclusions. Health care expenditures for back pain in the United States in 1998 were substantial. The expenditures demonstrated wide variations among individuals with different clinical, demographic, and socioeconomic characteristics. [Key words: health care expenditures, back pain, expenditure pattern] Spine 2004;29:79 – 86 From the *Center for Clinical Effectiveness and †Division of Orthopedic Surgery, Department of Surgery, Duke University Medical Center, Durham, North Carolina; and ‡Pharmaceutical Policy & Evaluative Sciences, School of Pharmacy, University of North Carolina, Chapel Hill, North Carolina. Acknowledgment date: February 4, 2003. First revision date: April 24, 2003. Acceptance date: April 30, 2003. The manuscript submitted does not contain information about medical device(s)/drug(s). No funds were received in support of this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript. Address correspondence to Xuemei Luo, PhD, DUMC 3645, Duke University Medical Center, Durham, NC 27710; E-mail: [email protected] Back pain is highly prevalent in the United States. Approximately 80% of Americans experience at least one episode of back pain during their lifetime1,2 and 15% to 20% tend to report back pain some time in a 1-year period.1 Because of its high prevalence, back pain is a leading reason for physician visits, hospitalization, and utilization of other health care services.3 Despite its importance, no recent studies have investigated health care expenditures and expenditure patterns for individuals with back pain in the United States using a nationally representative database. Information regarding health care expenditures of a particular disease is important for health care policy making since it affects the allocation of limited resources among different conditions.4 To our knowledge, only a limited number of studies have been conducted to estimate the health care costs for back pain in the United States. Grazier et al conducted the most comprehensive cost analysis in 1984,5 estimating the U.S. back pain costs using three 1977 national survey data sets and subsequently adjusting all costs to 1984 dollars. These authors found that the direct costs for back pain reached $12.9 billion annually.5 Frymoyer et al later adjusted the Grazier et al estimates to 19906 and 1994 dollars.7 Their adjusted estimates were $24.3 billion in 1990 and $33.6 billion in 1994. It is clear from these previous studies that back pain has imposed huge burdens on the U.S. health care system. In recent years, the United States has been facing the challenge of skyrocketing health care expenditures, with health care expenditures reaching $1.2 trillion and accounting for 13.6% of gross domestic product.8 Since back pain is one of the most costly diseases,9 it is important to identify the determinants of health care expenditures for this patient population. Such information can help developing optimal intervention strategies and appropriate health policies. Describing patterns of health care expenditures is often the first step toward understanding the determinants of the expenditures. A number of studies have been conducted to describe patterns of health care expenditures among back pain individuals. These studies found that a small percentage of high cost back pain patients accounted for most of the expenditures10,11 and that the expenditures were distributed disproportionately among workers with different duration of disability.12 An overview of the current literature on the estimates and patterns of health care expenditures for back pain in 79 80 Spine • Volume 29 • Number 1 • 2004 the United States indicates several limitations. First, the estimates are relatively outdated. The most comprehensive cost estimates were obtained in 1984 and the primary data sources had to be traced back to 1977.5 Although Frymoyer et al adjusted the above estimates to 1994, their cost estimates were based on various assumptions that may or may not be true in the real world.7 Moreover, because their calculation was based on previous estimates, the approach combined the limitations of previous studies and those of its own. Second, previous studies that estimated health care costs for back pain had a major methodology limitation. The estimates were based on health care services that back pain was the primary diagnosis.5 But back pain may cause complications such as depression13 or may increase the severity of other health problems. The expenditures associated with these conditions were not included, and such exclusions may cause underestimation of the costs. Finally, few studies have examined the patterns of health care expenditures in back pain population at a national level. Previous studies in this area were either conducted in a single state or the study subjects were limited to a specific patient population such as industry workers.10 –12 It is difficult to generalize the results nationally. Moreover, previous studies mostly focused on expenditure distribution or the variation of expenditures among people with different levels of disability. How health care expenditures varied among individuals with different demographic and socioeconomic characteristics has not been well established. One purpose of this study was to use a national survey database, 1998 Medical Expenditure Panel Survey (MEPS), to estimate U.S. health care expenditures for back pain in 1998. Recognizing the methodological limitations associated with previous studies, we took a different and broader approach. We first estimated total health care expenditures incurred by individuals with back pain. The strength of this method is that all relevant expenditures are included. But the approach allows the estimates to include not only expenditures related to back pain but also expenditures unrelated to back pain. To acquire more precise estimates, we subsequently calculated the incremental expenditures attributable to back pain among these individuals. We hoped that our estimates would provide policy makers and health care providers most up-to-date information about the U.S. health care expenditures for back pain and help the formulation of health care policies for back pain care in the United States. Another purpose of this study was to use the 1998 MEPS to describe health care expenditure patterns among individuals with back pain in the United States. We focused on describing how the expenditures were distributed and how the expenditures varied among individuals with different demographic, clinical, and socioeconomic characteristics. We hope that such descriptive information will guide future studies to identify the determinants of health care expenditures for back pain population and ultimately help better design intervention strategies and appropriate policies in an attempt to provide most cost-effective back pain care. Methods Data Source. The household survey of the 1998 MEPS was used as the data source for this study. The MEPS is cosponsored by the Agency for Healthcare Research and Quality and the National Center for Health Statistics. It is designed to provide nationally representative estimates of health care use, expenditures, source of payment, and insurance coverage for the civilian noninstitutionalized population of the United States.14 Detailed information about the MEPS can be found at Agency for Healthcare Research and Quality web site.14 Study Population. The study population was comprised of survey respondents who were 18 years of age and older. Back pain was defined as pain experienced in all back areas, regardless of upper or lower part of the back. This included any of the following three conditions: back disorders, disc disorders, and back injuries. ICD-9 codes used to identify individuals with back pain included 720, 721, 722, 723, 724, 805, 806, 839, 846, and 847. A total of 2,120 respondents reported back pain sometime during 1998. Since the MEPS is a sampling survey, these individuals are a representative sample of the 25.9 million adults having back pain in the United States in 1998. Health Care Expenditures. Health care expenditures were defined as sum of direct payments for the care provided during 1998. In contrast to the studies of cost of illness, in which the costs for uncompensated care are included, this study only considered the health care services for which payments were made. Our estimates of health care expenditures included expenditures associated with the following services: inpatient care, outpatient services, office-based visits, emergency room visits, prescription drugs, home health services, dental care, vision aids, and medical equipment purchase. Both office-based and outpatient services included visits not only to physicians, but also to nonphysician providers such as chiropractors, physical therapists, occupational therapists, psychologists, nurse and nurse practitioners, social workers, and physician’s assistants. Because MEPS is a survey of noninstitutionalized population, expenditures associated with nursing home care were not included. The health care expenditures were examined from a societal perspective, including out-of-pocket payments and payments by all payers, including private insurance, Medicaid, Medicare, Worker’s Compensation, and other sources. Data Analysis. The MEPS is a stratified multistage complex design survey. To account for such complex survey design, all estimates presented in the text and tables have been weighted to reflect national estimates and the standard errors were calculated by using PROC SURVEYMEAN AND PROC SURVEYREG (SAS Institute, version 8, Cary, NC). Total Health Care Expenditures Among Individuals With Back Pain. Total health care expenditures incurred by individuals with back pain were estimated by summing overall health care expenditures across all back pain individuals. We also divided total expenditures by number of individuals with back pain to obtain an estimate of per-capita health care expenditures. Direct Health Care Expenditures • Luo et al 81 Increment in Health Care Expenditures Attributable to Back Pain. Average increment in health care expenditures attributable to back pain was first computed. It was calculated as the extra expenditures incurred by individuals with back pain over the expenditures caused by individuals without back pain. To adjust for the potential difference in sociodemographic characteristics between the two groups of people, a multivariate regression model was estimated. For the model, variable total health care expenditures was specified as a function of back pain and sociodemographic factors, including age, sex, marital status, race, educational level, family income, and health insurance status. The average increment in total health care expenditures attributable to back pain was therefore calculated as the difference in adjusted mean expenditure between individuals with back pain and individuals without back pain. Total incremental health care expenditures were subsequently computed by multiplying the average incremental expenditures with number of individuals with back pain. In addition to the total incremental expenditures, we also built separate models estimating incremental expenditures for each health service. Expenditure data generally do not have normal distribution and have been transformed into various ways to improve its distribution. We did not make any transformation of the expenditure variable in this study for the following three reasons. First, there is no consensus about whether transformation or untransformation fits expenditure data better. Some studies recommended against using untransformed data,15,16 whereas others suggested that models based on untransformed data actually performed better than models based on transformed data.17,18 Second, the sample involved in our study was not small. When a data set is very large, ordinary least square regression on untransformed data will provide unbiased estimates of regression parameters.18,19 Third, regression models based on untransformed data do not require retransformation and can be easily interpreted. Expenditure Patterns Among Individuals With Back Pain. The expenditure patterns were examined by stratifying individuals with back pain by sociodemographic characteristics and medical diagnosis, followed by the calculation of percapita expenditures for each stratum. Investigated characteristics included age, gender, race, education, family income, and medical insurance. Family income was determined by the household income as a percentage of the federal poverty guideline and grouped into five categories: negative or poor, near poor, low income, middle income, and high income. Medical insurance was categorized as publicly insured, privately insured, and uninsured. A very important characteristics, Worker’s Compensation insurance, was not investigated in this study because of a lack of information in the investigated database. Individuals in each category of medical insurance may or may not have Worker’s Compensation benefits. Results Health Care Expenditures Among Individuals With Back Pain A total of 25.9 million adults reported back pain sometime in 1998. For this back pain population, more than 50% were female (55%) and about 61% were married. The average age was 48 years. The majority were white (88.3%). The most prevalent back diagnosis was ICD 724, which included spinal stenosis, lumbago, sciatica, Table 1. Characteristics Among Individuals With Back Pain (N ⴝ 25.9 million) Age (yr) Gender (%) Female Male Education (%) ⬍12 grade ⱖ12 grade Marital status (%) Married Widowed or separated or divorced Single Race (%) White Black Other Diagnosis* (%) Ankylosing spondylitis and other inflammatory spondylopathies (ICD 720) Spondylosis and allied disorders (ICD 721) Intervertebral disc disorders (ICD 722) Other disorders of cervical region (ICD 723) Other and unspecified disorders of back (ICD 724) Fracture of vertebra without mention of spinal cord injury (ICD 805) Fracture of vertebra with spinal cord injury (ICD 806) Other, multiple, and ill-defined dislocations (ICD 839) Sprains and strains of sacroiliac region (ICD 846) Sprains and strains of other and unspecified parts of back (ICD 847) 47.9 55.0 45.0 19.2 80.8 60.9 23.8 15.3 88.3 8.1 3.6 0.3 5.1 14.2 9.6 59.5 2.2 0.03 2.1 2.2 16.2 * The sum of the percentage for each diagnosis is larger than 100%. This is because some people have more than one diagnosis. and other unspecified back disorders (59.5%). Other diagnoses that had prevalence larger than or close to 10% were ICD 847 (back sprains and strains; 16.2%), ICD 722 (disc disorders; 14.2%), and ICD 723 (other disorders of cervical region; 9.6%) (Table 1). Total health care expenditures incurred by individuals with back pain in the United States in 1998 were approximately $91 billion. The expenditures for inpatient care ($27.9 billion) accounted for the largest proportion of the total expenditures (31%), followed by the expenditures for office-based visits ($23.6 billion, 26.0%). Other health care services responsible for more than 10% of the total expenditures included prescription drugs ($14.1 billion, 15.6%) and outpatient service ($11.9 billion, 13.1%). Emergency room visits ($2.7 billion) and home health services ($2.7 billion) contributed the least to the total expenditures, each accounting for 3% of the total expenditures. Table 2 summarizes per-capita expenditures in 1998 for individuals with back pain and individuals without back pain. The per-capita total expenditures for individuals with back pain were $3,498, compared with $2,177 for individuals without back pain. Back pain individuals therefore incurred total health care expenditures about 1.6-fold higher, on average, than individuals without back pain. Investigation of each health service demonstrated that individuals with back pain had higher percapita expenditures across all services than individuals without back pain (Table 2). 82 Spine • Volume 29 • Number 1 • 2004 Table 2. Comparison of Health Care Expenditures Between Individuals With Back Pain and Individuals Without Back Pain (N ⴝ 198.7 million) Per Capita Expenditures ($) Service Type Individuals With Back Pain (N ⫽ 25.9 million) Individuals Without Back Pain (N ⫽ 172.7 million) Ratio of Back Pain to Non-Back Pain Individuals Office-based Outpatient Emergency room visits Inpatient Home health Prescription drugs 910.0 460.4 102.7 1,075.7 105.5 541.5 425.9 248.8 61.5 774.4 92.2 340.1 2.1 1.9 1.7 1.4 1.1 1.6 Total 3,498.1 2,177.9 1.6 Incremental Expenditures Attributable to Back Pain The increment in health care expenditures attributable to back pain was calculated. Back pain caused a per-capita increment of $1,014.6 in overall service expenditures. Multiplying this estimate by the number of individuals with back pain (25.9 million), the total incremental expenditures attributable to back pain reached 26.3 billion. When investigated by each service, office-based visits had the highest per-capita incremental expenditures ($428.4), followed by outpatient services ($181.3), inpatient care ($173.4), prescription drugs ($148.7), and emergency room visits ($40.5). The per-capita incremental expenditures for home health services was negative (⫺$7.4), suggesting that individuals with back pain incurred lower home health expenditures than individuals without back pain. Multiplying the per-capita incremental expenditures with the number of individuals with back pain, the sum of incremental expenditures for office-based visits exceeded $10 billion ($11.1 billion). The sum of incremental expenditures for the other services was neither small: $4.7 billion for outpatient services, $4.5 billion for inpatient care, $3.9 billion for prescription drugs, and $1.1 billion for emergency room visits. Patterns of Health Care Expenditures Among Individuals With Back Pain The health care expenditures were not equally distributed among individuals with different levels of expenditures. Table 3 shows the percentage of service expenditures attributable to the high expenditure cases. For each health service, the 10% most expensive individuals accounted for ⬎50% of the service expenditures. The 25% most expensive individuals accounted for ⬎75% of the service expenditures. The 50% most expensive individuals accounted for 90% to 100% of the service expenditures (Table 3). Such pattern was particularly clear for inpatient care, outpatient services, and emergency room visits. Close to 100% of the expenditures for inpatient care, 87% for outpatient services, and 90% for emergency room visits were accounted for by the 10% most expensive individuals (Table 3). Per-capita expenditures varied among individuals with different back pain diagnoses (Table 4). Only diag- noses with prevalence ⬎5% were investigated. Individuals with disc disorders and individuals with spondylosis and allied disorders had per-capita total expenditures exceeding $5,000, with disc disorder individuals incurring the highest per-capita expenditures ($6,010.7). As a comparison, the per-capita total expenditures for individuals with spinal stenosis, lumbago, sciatica and other unspecified back disorders (ICD 724) and individuals with other disorders of cervical region (ICD 723) were much lower, with each reaching close to or less than $3,500. Individuals with back sprains and strains had even lower per-capita total expenditures (Table 4). Analysis of each health service indicated that the per-capita expenditures for office-based visits and emergency room visits were not dramatically different among individuals with different diagnoses. Per-capita expenditures for home health services were also similar except that individuals with back sprains and strains had much lower per-capita expenditures than the other groups (Table 4). The per-capita expenditures for inpatient care were very different among different diagnosis groups. Individuals with disc disorders had the per-capita inpatient care expenditures reaching $2,816, compared with only $634 for individuals with back sprains and strains. Per-capita expenditures for outpatient services and prescription drugs were also different among different diagnosis groups but not so dramatic as that for inpatient care (Table 4). Table 3. Percentage of Service Expenditures Attributable to the Top Expenditure Individuals Service Type Office-based Outpatient Emergency visit Inpatient Prescription drugs Top 10% by Expenditures/ % of Total Expenditures* Top 25% by Expenditures/ % of Total Expenditures Top 50% by Expenditures/ % of Total Expenditures 51.8 86.6 90.2 98.7 52.5 76.0 99.96 100 100 80.5 93.0 100 100 100 96.6 * This percentage was calculated as following: sum of expenditures for individuals whose service expenditures were on top 10%/total expenditures for the service. Direct Health Care Expenditures • Luo et al 83 Table 4. Per-Capita Expenditures ($) Among Back Pain Individuals With Different Diagnosis Diagnosis N (millions) Office-Based Outpatient Emergency Visit Inpatient Home Health Prescription Drug Total 1.3 1043.7 545.3 122.5 2033.4 167.9 877.6 5042.2 3.7 1157.5 725.1 111.8 2816.4 131.5 785.5 6010.7 2.5 1088.6 410.7 136.3 821.2 140.4 380.4 3336.5 15.4 931.0 513.6 87.8 973.5 124.6 530.8 3513.6 4.2 841.1 252.5 121.0 634.0 12.2 417.5 2494.4 ICD721: spondylosis and allied disorders ICD722: intervertebral disc disorders ICD723: other disorders of cervical region ICD724: other and unspecified disorders of back ICD847: sprains and strains of other and unspecified parts of back The per-capita expenditures varied among individuals with different demographic and socioeconomic characteristics. As shown in Table 5, the per-capita total expenditures or per-capita expenditures for each service were different among different age groups. Except emergency room visits, as age increased, the per-capita expenditures also increased (Table 5). Like age, except emergency room visits, the per-capita expenditures for each service or the per-capita total expenditures were different between different gender groups, with females incurring higher expenditures, on average, than males (Table 5). Such difference also existed among different race groups, with whites generally having higher per-capita expenditures than blacks or other races (Table 5). However, for individuals having different levels of education, the difference in per-capita expenditures was not consistent across all services. For office-based visits and home health services, individuals with an education at the 12th grade level or above had higher per-capita expenditures when compared with their counterparts. But for other services, the results were the opposite (Table 5). The investigation of per-capita service expenditures or percapita total expenditures among individuals with different levels of family income did not demonstrate any clear trend (Table 5). Finally, except for emergency room visits, individuals with either private or public insurance incurred higher per-capita total expenditures and higher per-capita expenditures for each service than uninsured. Among the insured, individuals with public insurance had higher per-capita total expenditures and higher percapita expenditures for all services, except emergency room visits, than privately insured (Table 5). Discussion Our analysis indicates that the total health care expenditures incurred by individuals with back pain in the Table 5. Per-Capita Expenditures ($) Among Individuals With Different Characteristics Characteristic Age (yr) 18–44 45–64 ⱖ65 Gender Male Female Race White Black Other Education ⬎12 grade ⱕ12 grade Family income Negative or poor Near poor Low income Middle income High income Insurance Any private Public only Uninsured N (millions) Office-Based Outpatient Emergency Visit Inpatient Home Health Prescription Drug All Services 12.4 8.7 4.8 718.6 925.4 1378.7 369.9 462.6 691.5 107.3 72.7 145.7 582.3 1046.3 2407.8 19.0 41.6 446.4 285.4 647.2 1012.9 2334.7 3538.8 6443.8 11.7 14.3 657.9 1116 376.3 529.1 102.5 102.9 887.7 1229.2 28.1 168.7 398.7 658.2 2708.9 4142.9 22.9 2.1 0.96 941.3 655.8 723.5 479.1 377.3 198.3 98.3 144.4 117.1 1148.3 589.5 414.0 108.5 77.5 94.7 555.6 477.9 345.7 3647.9 2519.2 2083.4 12.9 13.0 965.4 854.0 460.3 464.3 86.8 118.4 547.8 1607.3 114.5 97.0 475.5 605.0 3027.5 3976.3 2.6 1.0 3.2 8.6 10.6 741.7 1046.7 1061.9 856.4 936.1 293.1 633.4 401.3 545.1 433.3 129.7 64.4 82.4 116.5 94.7 1142.8 839.4 1283.9 1226.3 896.9 221.8 227.9 422.8 31.7 31.3 639.8 639.3 654.3 572.2 450.0 3438.8 3700.1 4104.9 3606.1 3224.7 19.3 4.0 2.6 953.0 1088.9 307.5 476.4 636.7 65.1 102.7 97.8 110.7 880.4 2534.1 262.0 26.5 551.9 0.4 485.6 950.7 321.7 3256.3 6124.6 1208.5 84 Spine • Volume 29 • Number 1 • 2004 United States in 1998 reached approximately $91 billion and the incremental expenditures attributable to back pain totaled $26 billion. Because our estimates did not include the expenditures for nursing care, they are likely to be lower than the real value. Even with the underestimation, the health care expenditures for back pain in the United States are staggering. The $90 billion spent on behalf of the individuals with back pain accounted for about 1% of the gross domestic product in 1998,20 whereas the $26 billion incremental expenditures attributable to back pain represented about 2.5% of national health care expenditures for that year.21 Consistent with previous estimates, these findings demonstrate that the economic impacts of back pain in the United States are enormous. Estimates of the Health Care Expenditures for Back Pain The health care expenditures for back pain have been estimated in 1977 using national survey data.5 As compared with this earlier publication, the biggest strength of our study is the use of the 1998 MEPS, a very current national data on health care expenditures. After 1977, significant changes have occurred in the U.S. health care system. The most dramatic change is probably the rapid penetration of managed care.22 In the meantime, more aggressive prevention methods have been developed and new technologies and drugs have emerged. There have also been changes in health care policy, such as the introduction of federal guidelines.23 All these changes can impact the health care costs of back pain but were unable to be accounted for in the earlier studies. Using the current data allows us to provide more accurate estimates than the earlier studies. Different method and different data sources make it difficult to directly compare our estimates with those from earlier studies. But we still made the comparison since it allowed us to examine the trend of health care expenditures for back pain in the United States. Because the study by Frymoyer et al7 was based on the estimates from Grazier et al,5 we include in our comparison only the Grazier et al estimates. Also, because total health care expenditures include expenditures related to back pain and unrelated to back pain, the comparison was made by only using estimates of the incremental expenditures attributable to back pain. The comparison showed two interesting trends. First, in the Grazier et al5 estimates, the costs for hospital inpatient care (hospital service plus physician inpatient care) accounted for the largest proportion (about 40%) of the total back pain costs.5 However, in our incremental estimates, inpatient care accounted for only about 17% of the total incremental expenditures. Unlike the study by Grazier et al,5 the expenditures for nursing home care were not included in our total estimates. Based on their study, such expenditures accounted for about 20% of total expenditures for back pain. If we included the expenditures based on the estimates by Grazier et al,5 the percentage of the total incremental expenditures attributable to inpatient care should be even lower. The decline of inpatient expenditures observed in our study may be partly caused by the penetration of the managed care as studies demonstrated that individuals with managed care plans tended to have lower hospital admission rates and shorter hospital length of stay than individuals with a traditional indemnity plan.24 The decline in inpatient care services is expected to result in a higher use of physician offices and outpatient services as well as higher expenditures for these services. Indeed, in our estimates, office-based visits and outpatient services contributed to about 50% of the total incremental expenditures even after we considered the potential nursing home expenditures. This is in contrast to 16% in the Grazier et al5 estimates. The second interesting trend was observed for drug expenditures. In the estimates by Grazier et al, drug expenditures accounted for ⬍1% of total health care costs for back pain.5 But in our estimates, drug expenditures accounted for ⬎10% of the total incremental expenditures. Investigation of all service expenditures shows that the increase of drug expenditures is the most rapid. This is in agreement with general consensus that drug expenditures increased at a very rapid speed in recent years.25 How to control drug expenditures for back pain may deserve special attention in the future. Patterns of Health Care Expenditures Among Individuals With Back Pain The enormous health care expenditures incurred by individuals with back pain indicate a need to effectively control such expenditures. Examining the expenditure patterns is our first step to achieve this goal. In this study, we found that a small percentage of high expenditure individuals accounted for a large proportion of the total health care expenditures. Previous studies using data from industry workers or enrollees of insurance programs found similar results.10,11 Also, consistent with previous studies,10 we found that back pain individuals with disc disorders incurred much higher per-capita expenditures than individuals with other back pain diagnoses, especially those with back strains or sprains. A closer examination of the expenditures for each health service among individuals with disc disorder indicated that the inpatient expenditures accounted for nearly 50% of the total expenditures and their per-capita inpatient expenditures were much higher than that of individuals with other diagnoses. How to prevent the health care expenditures for disc disorder patients, especially the inpatient expenditures, deserves special attention in the future. The health care expenditures also varied among back pain individuals with different demographic and socioeconomic characteristics. In this patient population, the elderly incurred higher expenditures, on average, than younger individuals, which is consistent with the results observed in the general population.26 It is interesting to find that females incurred higher expenditures, on aver- Direct Health Care Expenditures • Luo et al 85 age, than males. The reason for the difference is not clear and needs further investigation. The findings that whites had higher per-capita expenditures than blacks or other races and that per-capita expenditures were much higher for medically insured versus the uninsured suggest that there may be barriers of access to care among back pain individuals who were blacks or medically uninsured. Finally, we found that publicly insured incurred much higher expenditures, on average, than privately insured, especially for expenditures in inpatient care, home health service, or prescription drugs. Because both these groups were insured, it would be interesting to investigate whether the difference in the expenditures is caused by the difference of insurance programs. graphic, socioeconomic, and clinical factors impact the health care expenditures of these individuals. Key Points ● Health care expenditures for back pain in the United States in 1998 were substantial. ● Health care expenditures demonstrated wide variations among back pain individuals with different clinical, demographic, and socioeconomic characteristics. References Limitations This study is constrained by several limitations. First, our expenditure estimates may be understated. As discussed above, we did not include expenditures associated with nursing home care, which accounted for about 20% of total health care expenditures for back pain in the previous studies.5 Moreover, we used ICD-9 codes to determine back pain, and the ICD 9 codes in the MEPS were limited to major categories (3-digit codes) with no subclassification. Individuals with infectious or malignant back pain may have been classified under the main ICD categories such as infectious diseases or neoplasm. As a consequence, the expenditures for these cases may have been missed from the estimation. Second, because of the lack of information about disability in the MEPS, we did not examine how health care expenditures differed between individuals who were not disabled and individuals who were disabled by back pain, especially those with chronicle disability. This is an important issue since previous studies found that 5% of people with back pain disability accounted for 75% of direct and indirect costs for back pain2 and the costs rose at an accelerating rate as the duration of disability increased.11 Finally, also because of the lack of information, we did not analyze how the expenditures were different between individuals receiving and not receiving Worker’s Compensation benefits. It is important to examine Worker’s Compensation since it had a negative impact on the length of disability and the recovery from back pain3 and was a major contributor to back pain costs.11 Conclusion This study provides an important descriptive analysis of health care expenditures and expenditure pattern for back pain population in the United States. The health care expenditures for this patient population are enormous and also vary widely across individuals with different clinical, socioeconomic, and demographic characteristics. 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