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A Systematic Review of Low Back Pain Cost of Illness Studies in the United States and Internationally

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  A systematic review of low back pain cost of illness studiesin the United States and internationally Simon Dagenais, DC, PhD a,b, *, Jaime Caro, MD c,d , Scott Haldeman, DC, MD, PhD e,f ,g a  Division of Orthopaedic Surgery and Department of Epidemiology and Community Medicine,Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada b CAM Research Institute, Irvine, CA, USA c  Division of General Internal Medicine and Department of Epidemiology, Biostatistics and Occupational Health,Faculty of Medicine, McGill University, Montreal, QC, Canada d Caro Research Institute, Concord, MA, USA e  Department of Neurology, University of California, Irvine, CA, USA f   Department of Epidemiology, University of California, Los Angeles, CA, USA g  Research Division, Southern California University of Health Sciences, Whittier, CA, USA Received 25 September 2007; accepted 13 October 2007 Abstract BACKGROUND CONTEXT:  The economic burden of low back pain (LBP) is very large andappears to be growing. It is not possible to impact this burden without understanding the strengthsand weaknesses of the research on which these costs are calculated. PURPOSE:  To conduct a systematic review of LBP cost of illness studies in the United States andinternationally. STUDY DESIGN/SETTING:  Systematic review of the literature. METHODS:  Medline was searched to uncover studies about the direct or indirect costs of LBPpublished in English from 1997 to 2007. Data extracted for each eligible study included study de-sign, population, definition of LBP, methods of estimating costs, year of data, and estimates of di-rect, indirect, or total costs. Results were synthesized descriptively. RESULTS:  The search yielded 147 studies, of which 21 were deemed relevant; 4 other studies and 2additionalabstractswerefoundbysearchingreferencelists,bringingthetotalto27relevantstudies.Thestudies reported on data from Australia, Belgium, Japan, Korea, the Netherlands, Sweden, the UK, andthe UnitedStates. Ninestudies estimated directcosts only, nine indirectcosts only, and nine both directandindirectcosts,fromasocietal(n 5 18)orprivateinsurer(n 5 9)perspective.Methodologyusedtode-rivebothdirectandindirectcostestimatesdifferedmarkedlyamongthestudies.Amongstudiesprovid-ing a breakdown on direct costs, the largest proportion of direct medical costs for LBP was spent onphysical therapy (17%) and inpatient services (17%), followed by pharmacy (13%) and primary care(13%).Amongstudiesprovidingestimatesoftotalcosts,indirectcostsresultingfromlostworkproduc-tivity represented a majority of overall costs associated withLBP. Three studies reported that estimateswith the friction period approach were 56% lower than with the human capital approach. CONCLUSIONS:  Several studies have attempted to estimate the direct, indirect, or total costs as-sociated with LBP in various countries using heterogeneous methodology. Estimates of the eco-nomic costs in different countries vary greatly depending on study methodology but by anystandards must be considered a substantial burden on society. This review did not identify any stud-ies estimating the total costs of LBP in the United States from a societal perspective. Such studiesmay be helpful in determining appropriate allocation of health-care resources devoted to thiscondition.    2008 Elsevier Inc. All rights reserved. Keywords:  Low back pain; Cost of illness; EconomicsFDA device/drug status: not applicable.Nothing of value received from a commercial entity related to thismanuscript.* Corresponding author. 25 Corona Ave., Rockcliffe, ON, K1M 1K8,Canada. Tel.: (949) 466-8132; fax: (949) 266-8951. E-mail address : simon@camresearch.com (S. Dagenais)1529-9430/08/$ – see front matter    2008 Elsevier Inc. All rights reserved.doi:10.1016/j.spinee.2007.10.005The Spine Journal 8 (2008) 8–20  Introduction The focus of this special focus issue of   The Spine Jour-nal  is on the management of chronic low back pain(CLBP). This topic was chosen partly because of its impos-ing socioeconomic burden, which appears to be increasingrapidly despite technological advances in diagnosis andthe introduction of numerous interventions in recent years.The general pessimism surrounding the prognosis of CLBPis such that few clinicians, researchers, or third-partypayers would dispute any proposed cost estimate, no matterhow large it may appear. Such views are understandablewhen faced with a prevalent, disabling, clinically challeng-ing, and seemingly expensive condition such as CLBP.However, it is essential to understand the precise magnitudeof the economic burden of CLBP before examining poten-tial cost-saving solutions or comparing the cost effective-ness of competing interventions. This can be achieved byreviewing cost of illness studies.Cost of illness studies summarizing the economic bur-den of a particular disease must be considered by allstakeholders, including patients, clinicians, and third-partypayers when deciding on the allocation of scarce health-care resources [1]. It should be noted that cost of illnessstudies serves a different purpose than health economicevaluations (eg, cost-benefit analysis, cost-effectivenessanalysis, cost-utility analysis), which are focused on evalu-ating the costs of interventions rather than estimating thecost of a particular disease [1]. The purpose of this studywas to conduct a systematic review of CLBP cost of illnessestimates in the United States and internationally. To helpreaders understand some of the basic principles of healtheconomics pertinent to the studies summarized in this re-view, a brief overview of important concepts related to costof illness studies is presented below. Cost of illness studies The economic burden of a disease is the sum of all costsassociated with that condition which would not otherwisebe incurred if that disease did not exist. Given the many cat-egories of costs that must be considered, it can be challeng-ing to fully estimate the economic burden of an illness asdata are often unavailable. The term ‘‘cost’’ in health eco-nomics refers to the value of the consequences of usinga particular good or service rather than its price. That valuecorresponds to the best alternative use of those resources,which is termed the opportunity cost. The difference be-tween cost and price can be demonstrated by comparingwhat a clinician charges for his services versus the amountactually reimbursed for those services; the latter may bea better proxy of true cost than the former. Despite this ex-ample, it should be made clear that estimating the economicburden of a disease is not simply a matter of tabulating theamount reimbursed for all clinician services related to a par-ticular diagnosis. The total cost of illness d or economicburden d has three components: (1) direct (medical andnonmedical) costs; (2) indirect costs; and (3) intangiblecosts.  Direct costs Direct costs refer to those that, at least in principle, in-volve a monetary exchange. Direct medical costs are mostfamiliar to readers and commonly include costs incurred forphysician services, medical devices, medications, hospitalservices, diagnostic testing, etc [2]. The term direct health-care costs may be more accurate because allied health,complementary and alternative medicine (CAM), and othernonphysician costs are included. Direct medical costs aretypically the easiest to estimate because records are keptof such transactions by clinicians, third-party payers,employers, or patients.Direct nonmedical costs are those related to goods andservices consumed directly because of the illness but whichare not considered to be health care related. They include,for example, transportation or other travel costs to attendmedical appointments, meals eaten outside the home whenreceiving health care, renovations to make a house more ac-cessible for those who may become physically disabledsecondary to a disease, and so on. These expenses are easyto overlook when considering the economic burden of a dis-ease but can constitute an important source of related costs.  Indirect costs Indirect costs are those reflecting the economic value of consequences for which there is no direct monetary trans-fer. They commonly include costs related to employmentand household productivity. Employment costs includeboth work absences resulting in foregone productivity(termed ‘‘absenteeism’’) and decreased productivity forthose who continue to work despite being affected by theircondition (termed ‘‘presenteeism’’) [3]. Indirect costs areoften more difficult to measure than direct costs. For exam-ple, it is nearly impossible to determine whether presentee-ism is in fact occurring and which medical condition, if any,is primarily responsible for its occurrence. Such productiv-ity losses can be estimated by interviewing workers andasking them to evaluate their own reduced productivity asit relates to their health status, or by interviewing theirsupervisors and asking for their opinions about whethera particular worker’s productivity has changed secondaryto a disease. Rarely can such presenteeism costs be mea-sured objectively or with certainty. Absenteeism costs aregenerally easier to estimate because employer records andworkers’ compensation insurance systems will notehealth-related work absences.  Human capital and friction cost approaches There is debate among economists about the preferredmethods for estimating indirect costs, the majority of whichare often composed of lost productivity [3]. The most com-mon method is the human capital approach, which assumes 9 S. Dagenais et al. / The Spine Journal 8 (2008) 8–20  that the economic value of an employee’s productivity isequal to the cost of their salary and benefits [4]. Lost pro-ductivity is therefore estimated by calculating earnings lostduring work absences, regardless of the length of absence.This method would therefore calculate lost productivity fordisability-related early retirement as the value of lost earn-ings from the date of disability until that worker wouldhave reached normal retirement age (eg, 65 y). Employers,however, will eventually replace those employees that areabsent for extended periods and regain the value of the src-inal employee’s lost productivity. Thus, productivity lossesare truly only incurred from the worker’s absence for healthreasons until a replacement worker is hired, trained, and hasreached the productivity of the disabled employee. Thelength of time required for this transition to occur has beentermed the friction period and varies for different industriesand economic conditions based on factors that may influ-ence the time required to replace an employee (eg, unem-ployment level, job skill and education requirements, andlocation) [5]. Evaluating the cost of lost productivity withthis assumption has been termed the friction cost approach[4]. Alternatively, the cost of hiring replacement workersfor employees on disability leave may also be used to esti-mate lost productivity [3]. A combination of methods maybe most appropriate to estimate indirect costs by, for exam-ple, using the human capital approach for temporary pro-ductivity losses from absences that are shorter than thefriction period, and using the friction cost approach forlonger-term productivity losses.  Household productivity In addition to lost work productivity, individuals with anillness may also incur productivity losses at home if theyare unable to complete routine household tasks (eg, clean-ing, cooking, and maintenance). This is true whether theymust rely on paid outsiders to complete such tasks on theirbehalf, or whether unpaid household members must do so.These indirect costs can be estimated using the earnings of a hired household worker or by using an estimate of the na-tional or regional value of leisure time, which is typicallyless than the mean hourly wage.  Intangible costs The third type of cost that may be considered when es-timating the total cost of illness for a particular disease istermed intangible costs. These costs reflect the value of de-creased enjoyment of life because of illness. However,these costs are rarely included when estimating the eco-nomic burden of an illness because of general societal dis-comfort with placing a monetary value on these aspects of a disease. Cost perspectives The cost of an illness may be viewed from various per-spectives and depends on who bears the costs. Costs couldbe estimated from a patient perspective (eg, out-of-pocketcosts), employer perspective (eg, cost of worker’s compen-sation insurance premiums and lost productivity), insurancecompany perspective (eg, cost of claims paid), governmentperspective (eg, cost of public health services), or societalperspective, which would include all related costs. The lat-ter is the most comprehensive and broadest perspective andavoids underestimating costs when only considered froma narrower perspective. Sources of cost data The perspective chosen will also impact the types andsources of data used in the cost of illness study. Em-ployer, insurer, or government perspective may derive ac-ceptable cost estimates by apportioning claims in largeutilization databases to specific diagnoses, which has beentermed a top-down approach [4]. Alternatively, the patientperspective may extrapolate costs from interviews or dia-ries about health-care utilization and costs, which hasbeen termed a bottom-up approach [4]. The societal per-spective could combine both approaches to capture moredata. Methods A search of Medline was conducted on July 1, 2007, forstudies pertaining to the costs of low back pain (LBP) usingthe following strategy:1. *Back Pain/Economics2. low back pain.mp. or exp Low Back Pain/ 3. health care costs.mp. or exp Health Care Costs/ 4. cost of illness.mp. or exp Cost of Illness/ 5. health expenditures.mp. or exp health expenditures/ 6. exp Health Resources/Economics, Utilization7. exp Sick Leave/Economics8. 1 or (2 and (or/3-7))The search was limited to studies published in Englishfrom 1997 to 2007 to uncover relatively recent cost of ill-ness studies. Search results were screened for relevanceaccording to the eligibility criteria outlined below.Inclusion:1. Back pain or LBP2. Monetary estimate of direct or indirect costs3. Societal or insurer perspective.Exclusion:1. Neck pain only2. Economic evaluations of interventions (eg, cost-effec-tiveness analyses) 10  S. Dagenais et al. / The Spine Journal 8 (2008) 8–20  3. Details concerning only some specific direct costs(eg, prescription costs)4. Indirect costs expressed as lost work days withoutmonetary valuation5. Elderly patients only (eg, O 65 y)6. Review articles without new data.If information provided in search results was insufficienttodeterminestudyeligibility,full-textarticleswereretrievedfor further screening. The following data were extracted forall included studies:1. Case definition of LBP2. Cost perspective3. Cost types4. Country5. Estimated direct costs6. Estimated indirect costs7. Estimated total costs8. Prevalence of LBP according to case definition9. Study design and data sources10. Study population11. Year of data.For studies reporting detailed direct costs, portions at-tributable to each of the following (or similar) categorieswere extracted:1. Chiropractic (and osteopathy for studies outside theUnited States)2. CAM (eg, acupuncture, homeopathy, massage, andnaturopathy)3. Emergency department (ED)4. Imaging5. Inpatient6. Mental health7. Other8. Outpatient9. Pharmacy10. Physical therapy (PT)11. Primary care12. Specialists13. Surgery.For studies reporting detailed indirect costs, portions at-tributable to each of the following (or similar) categorieswere extracted:1. Early retirement2. Household3. Inactivity4. Presenteeism5. Sick leave.Because of considerable methodological heterogeneity,results were synthesized descriptively. Results The search strategy yielded 147 studies, of which 12(8%) were relevant, 114 (78%) were irrelevant because theydid not meet eligibility criteria, and 21 (14%) were of un-certain relevance based on information contained in thesearch records (eg, title, abstract). When full-text articleswere retrieved for the latter group, an additional eight stud-ies were deemed relevant; five additional studies were alsolocated by searching references of the studies obtained viaMedline. In addition, two relevant conference proceedingswere located, which were only available as abstracts.The methodology for the 27 relevant studies included inthis review is summarized in Table 1.Studies from Australia [6], Belgium [7], the Isle of Jer- sey [8], Japan [9], Korea [10], the Netherlands [2,11], Swe- den [4,5,12,13], the United Kingdom [14], and the United States [1,3,15–27] were obtained. All non-US studies(n 5 12) [2,4–14] and 5 of the US studies [1,15,20–22] ex- amined costs from a societal perspective; the other 10 USstudies used an insurer’s perspective to estimate costs. Most[1,3,4,6–9,11,13–16,19–27] took a top-down approach andallocated portions of total costs from national public or pri-vate insurer databases according to related internationalclassification of diseases (ICD)-9 or ICD-10 diagnostic co-des. Five top-down studies [4,6,7,13,14] also relied on dataprovided in prior surveys or utilization studies to help allo-cate costs for specific interventions to LBP. Because onlythree [2,12,21] had a temporal component (eg, O 6 mo) totheir case definition of LBP, it was not possible to limit thisreview to studies examining specifically CLBP.The prevalence of LBP as defined in each study rangedfrom 5% to 65%, with a mean of 18.7% and a standarddeviation (SD) of 4.6%. The mean time lag between theyear of data examined to derive cost estimates and the yearof study publication was 4.6 years (SD 0.5), with a range of 1 to 11 years. Four of the US top-down studies [1,17,26,27]used the Medical Expenditures Panel Survey (MEPS) andone [21] used its predecessor, the National Medical Expen-ditures Survey. There were three prospective cohort studies[2,5,10] that examined costs incurred by a defined group of patients over time based on health utilization or disabilitybenefit records. Only one study [2] used a bottom-up ap-proach with self-reported patient diaries documenting theuse and cost of health services related to LBP to supple-ment information contained in utilization databases. Onecross-sectional study [12] interviewed physicians to inquireabout the perceived use of health services in some of theirpatients with LBP, rather than interviewing patients di-rectly. Two studies [17,18] compared the use of health ser-vices by those with LBP to a control group of peoplewithout LBP.National LBP cost of illness estimates uncovered in thisreview are summarized in Table 2.Eight studies from five countries d Australia, Belgium,Japan, Sweden, and the UK  d estimated the total national 11 S. Dagenais et al. / The Spine Journal 8 (2008) 8–20
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