Chronic wound prevalence and the associated cost of treatment in Medicare beneficiaries: changes between 2014 and 2019

Abstract Objective To determine the cost of wound care and prevalence of chronic wounds for Medicare beneficiaries in the aggregate, by wound type, and by setting between the years 2014 and 2019. Methods This retrospective analysis of Medicare claims data included beneficiaries who experienced episodes of care for diabetic foot ulcers and infections; arterial ulcers; skin disorders and infections; surgical wounds and infections; traumatic wounds; venous ulcers and infections; unspecified chronic ulcers; and others. The 2014 data were based on a Medicare 5% Limited Data Set whereas for 2019 the data used were for all fee-for-service Medicare beneficiaries. Three methods were used to generate expenditure estimates: (a) a low (Medicare provider payments when the wound was a primary diagnosis, excluding any kind of deductible); (b) mid (primary plus secondary diagnosis with weighted attribution); and (c) high (primary or secondary diagnosis). The main outcomes were the prevalence of each wound type, Medicare expenditure for each wound type and aggregate, and expenditure by type of service. Results Over the 5-year period the number of Medicare beneficiaries with a wound increased from 8.2 million to 10.5 million. Wound prevalence increased by 13% from 14.5% to 16.4%. Over the 5-year period, the Medicare beneficiaries with the largest increase in chronic wound prevalence were those aged <65 years (males: 12.5% to 16.3%; females: 13.4% to 17.5%). The largest changes in terms of wound prevalence were increases in arterial ulcers (0.4% to 0.8%), skin disorders (2.6% to 5.3%), and decreases in traumatic wounds (2.7% to 1.6%). Expenditures decreased regardless of the three methods used with a reduction of $29.7 billion to $22.5 billion for the most conservative method. Except for venous ulcers in which costs per Medicare beneficiary increased from $1206 to $1803, cost per wound decreased with surgical wounds remaining the most expensive to treat (2014: $3566; 2019: $2504), and the largest decrease for arterial ulcers ($9651 to $1322). Hospital outpatient fees saw the largest reduction ($10.5 billion to $2.5 billion) although home health agency expenditures decreased from $1.6 billion to $1.1 billion. Physician offices saw an increase from $3.0 billion to $4.1 billion and durable medical equipment increased from $0.3 billion to $0.7 billion. Conclusions It appears that chronic wound care expenditures have shifted to the physician's office from the hospital-based outpatient department. Given that the prevalence of chronic wounds is increasing, especially among the disabled under 65, it will be important to know whether these shifts have positively or negatively affected outcomes. Highlights In 2014 chronic wounds impacted 14.5% of Medicare beneficiaries but this increased to 16.3% by 2019. The group of Medicare beneficiaries most affected in terms of chronic wound prevalence over the 5-year period were those aged <65 years (males: 12.5% to 16.3%; females: 13.4% to 17.5%). The largest changes in terms of prevalence were increases in arterial ulcers (0.4% to 0.8%), skin disorders (2.6% to 5.3%), and traumatic wounds (2.7% to 1.6%) Over the 5-year period, regardless of the method used, there was a decrease in chronic wound-related costs ($29.7 billion in 2014 to $22.5 billion in 2019 for the most conservative method: Medicare provider payments when the wound was a primary diagnosis, excluding any kind of deductible). Surgical complications still represent the largest wound category of costs with a small decrease from 2014 to 2019 of $6.1 billion to $5.9 billion. Based on the most conservative method, there was a very large cost reduction observed for outpatients from $10.5 billion to $2.5 billion with a correspondingly smaller decrease for inpatients of $5.3 billion to $4.2 billion, but an increase from $3.0 billion to $4.1 billion for physician offices. In addition, while durable medical equipment increased from $0.3 billion to $0.7 billion, home health agency expenditures decreased from $1.6 billion to $1.1 billion. Our data suggest that while most of the cost remains in the subacute setting it has shifted to the physician's office from the hospital-based outpatient department. Given the increasing prevalence of chronic wounds, especially among the disabled under 65, it will be important to know whether these shifts have positively or negatively affected outcomes.

In 2014 chronic wounds impacted 14.5% of Medicare beneficiaries but this increased to 16.3% by 2019.The group of Medicare beneficiaries most affected in terms of chronic wound prevalence over the 5-year period were those aged <65 years (males: 12.5% to 16.3%; females: 13.4% to 17.5%).The largest changes in terms of prevalence were increases in arterial ulcers (0.4% to 0.8%), skin disorders (2.6% to 5.3%), and traumatic wounds (2.7% to 1.6%)Over the 5-year period, regardless of the method used, there was a decrease in chronic woundrelated costs ($29.7 billion in 2014 to $22.5 billion in 2019 for the most conservative method: Medicare provider payments when the wound was a primary diagnosis, excluding any kind of deductible).Surgical complications still represent the largest wound category of costs with a small decrease from 2014 to 2019 of $6.1 billion to $5.9 billion.Based on the most conservative method, there was a very large cost reduction observed for outpatients from $10.5 billion to $2.5 billion with a correspondingly smaller decrease for inpatients of $5.3 billion to $4.2 billion, but an increase from $3.0 billion to $4.1 billion for physician offices.In addition, while durable medical equipment

Introduction
Chronic wounds represent a burden to society that is large, impacting the quality of life of nearly 2.5% of the total population in the United States 1 .The prevalence of chronic wounds 2 is similar to that of heart disease 3 , and some types of wounds, such as diabetic foot ulcers, have a mortality rate akin to cancer 4 .The elderly are more likely to develop chronic wounds compared to other age demographics as aging significantly affects the wound healing process 5 .Given the increasing age of the population, the continued threat of diabetes and obesity worldwide, and the persistent problem of infection, it is expected that chronic wounds will continue to be a substantial clinical, social, and economic challenge 6 .
In a previous study, we analyzed the Medicare 5% Limited Data Set (LDS) for calendar year 2014 for beneficiaries who experienced episodes of care for a variety of chronic wounds and infections to obtain prevalence data and to better estimate the cost of wound care in this population 6 .Since that time, escalating healthcare costs and concern over the variability of quality and outcomes have driven changes in the healthcare landscape.For example, the Center for Medicare and Medicaid Services (CMS) has accelerated the movement toward value-based care with the development and implementation of a myriad of alternate payment models and the quality payment program as part of the Affordable Care Act 7 .Episodic models, such as the Bundled Payment for Care Improvement (BPCI) sought to improve quality and reduce costs in hospitals, while Accountable Care Organizations (ACOs) were developed to encourage active population health management across the continuum of care as providers bear financial risk for enrolled patients 7 .Since 2000, there has been a shift away from acute care to hospitalbased outpatient departments (HOPD) and ambulatory surgical centers, which is why 2014 data showed that outpatient expenditures for wound care exceeded those in acute care.Since 2014, cost pressures in the HOPD, such as the package pricing (a bundling of services and products at an overall lower price) of relatively expensive cellular and/or tissuebased products for skin wounds (CTPs) have caused certain wound care services to start moving to office-based settings that were not subject to these pricing approaches.
The purpose of this study is to update our earlier analysis 6 (2014 data) of the prevalence and cost of wound care in the Medicare population using Medicare claims data.Thus, we collected complete Medicare data for the year 2019 with the intention of comparing 2014 versus 2019 data to determine (a) changes in chronic wound-related Medicare expenditures between the years 2014 and 2019 in total, by wound type, and type of service; and (b) changes in the prevalence of different wound types between the same years overall and by specific demographic groups.

Methods
Although the overall methodology used to obtain the data and analyze it was similar from 2014 to 2019, there were notable differences 6 (Table 1).

Databases
The 2014 database was the Medicare 5% Limited Data Set for the calendar year 2014, and all costs were evaluated for that 1-year time frame and calculated in 2014 US dollars.We inflated the 2014 cost figures to 2019 using the Medicare economic index, which was 6% over this period 9 .Medicare beneficiaries included in the analysis were those enrolled in Medicare Part A or B anytime during the year and not enrolled in a managed care plan.
The 2019 database was the Medicare Research Identifiable Files for the calendar year 2019, which included all Medicare fee-for-service claims and Medicare Advantage encounter data for 100% of Medicare beneficiaries.Medicare

Coding and prevalence
In this study, the populations examined are those Medicare beneficiaries who had an episode of care in 2014 or 2019 for a chronic wound defined as a skin disorder, surgical infection, diabetes infection, chronic ulcer, pressure ulcer, traumatic wound, venous infection, a venous ulcer, arterial ulcer, diabetic foot ulcer, and skin disease; and for 2019: radiation late effects, burns, and new 2020 codes.We used ICD-9 codes for the 2014 dataset and ICD-10 codes for the 2019 dataset (Table 1; full coding lists are available in the supplementary material).
As in the published 2018 study 6 , because beneficiaries can have multiple episodes of care for any wound type, we examined claims for all types of services and then computed the number of beneficiaries having any wound type taking care to avoid double counting of beneficiaries.For 2014 or 2019, the prevalence rates were calculated as the number of beneficiaries with any wound episode of care in the study year divided by the number of beneficiaries in the sample, with stratification by gender, age (65, 65-74, and !75 years), and wound type.

Medicare spending associated with wound care
The exact same methodology was used to determine the payment portion that can be attributed to each of the conditions the beneficiary had: (a) low range estimate (Medicare provider payments when the wound was a primary diagnosis, excluding any kind of deductible); (b) mid range estimate (similar to low range estimate but including the entire payment claim for the wound being the primary diagnosis and incorporating the following method of attribution when the wound was a secondary diagnosis): 1. Hospital inpatient, skilled nursing facility (SNF), home health agency (HHA), and hospice: each secondary diagnosis had equal weight and was attributed to half of the total cost of the stay.2. Hospital outpatient: all revenue centre-specific wound care service payments were assumed to be completely attributable to wound care while the balance (total paymentdirect wound care payments) was assigned by considering each secondary diagnosis to have an equal weight based on specific Healthcare Common Procedure Coding System (HCPCS) codes associated with wound care.and accorded half of the remaining amount.In addition, it was decided that for the cost of these services to be completely related to the cost of a wound, a wound diagnosis needed to be on the claim.
3. Part B provider (which includes physician charges) and DME (durable medical equipment): Medicare provider payments were counted if the claim level diagnosis code was associated with wound care.
The third method (c) counted Medicare provider payments when a wound was either the primary or secondary diagnosis and provides an upper bound estimate to total spending associated with wound care as this method assumes the wound is always the underlying cause of the service.For 2014, total Medicare spending estimates were extrapolated from the 5% sample to the entire Medicare feefor-service (FFS) population by multiplying each cost by 20.Spending attributable to wound care in the Medical Advantage population was estimated separately by assuming that it was proportional to FFS and total Medicare payments for MA plans equated to 28% of Medicare FFS spending 6,10 .For 2019 these corrections were unnecessary as the entire Medicare population (FFS and MA) was sampled.

Results
Over the 5-year period the number of Medicare beneficiaries with a wound increased from 8.2 million to 10.5 million (Table 2).In overall terms, wound prevalence increased over 5 years from 14.5% in 2014 to 16.4% in 2019 (Table 3).Three trends were observed from the demographic wound prevalence data.First, for pressure ulcers, chronic ulcers, and diabetic foot ulcers (DFUs), as well as DFU infections and surgical infections, there were substantive increases in the prevalence in the under-65-years age group compared to older groups regardless of gender; for example, an increase of 1.4% to 2.1% for males and 1.1% to 1.6% for females for pressure ulcers, and 3.2% to 4.7% for males and 3.1% to 4.2% for females for DFU infections.Second, the prevalence of surgical wounds, skin disorders, and arterial ulcers increased for all groups, but the greatest increases were again in the under-65-years age group (the increases in arterial ulcers and skin disorders were largely 2-3-fold).Last, the prevalence of traumatic wounds decreased substantially with the largest reduction seen in beneficiaries older than 65 years (Table 3).Medicare expenditures for wounds substantially decreased between 2014 and 2019 regardless of the cost attribution method used: (a) principal diagnosis: $29.7 billion to $22.5 billion; (b) principal diagnosis and attributed portion as secondary: $33.6 billion to $24.7 billion; and (c) principal diagnosis or any secondary: $102.6 billion to $67.1 billion (Table 4).Excepting venous ulcers and associated infections, in which moderate increases in expenditures were noted in all instances from 2014 to 2019, there was a decrease in expenditures for the majority of wound types regardless of the method used.For chronic ulcers methods (a) and (b) showed small increases while method (a) demonstrated a small increase for surgical wounds (Table 4).
When categories of service were examined, the most outstanding change was for hospital outpatients in which decreases of 76-89% in Medicare expenditures were observed depending on the method used (Table 5).Large increases for part B providers, DME, and hospice were noted, whereas, for hospital inpatients, SNF, and HHA, the increases or decreases were a lot smaller.Breaking down Medicare expenditures by fee-for-service or Medicare Advantage, most of the decrease likely occurred for FFS whereas, in the MA group, the changes were minimal (Table 4), with the caveats that because we did not have expenditure data for MA, we attributed FFS expenditures based on MA utilization and if Medicare Advantage limited the cost of care for patients with wounds by reducing services, we would not see an increase in cost there.When part B provider costs were examined in terms of place of service, the office and patient's home were by far the largest category for 2019 (2014 data not available): Office/home: $2.1 billion; inpatient/skilled nursing facility: $1.1 billion; all other places of service: $540 million; hospital-based outpatient: $435 million.
There were several changes in the mean expenditure for wound care per Medicare beneficiary by wound type (Table 6) showing that while arterial ulcers were the most expensive in 2014, pressure ulcers and surgical wounds have replaced them in 2019.For most wounds, there were decreases in expenditures, but chronic ulcers and venous leg ulcers and associated infections registered small-to-moderate increases.

Discussion
In comparison to our study of 2014 Medicare wound care data 6 , considerable changes have occurred in only 5 years.
The most important of these is the considerable drop in wound care expenditure.Previous estimates had a range of $29.7 billion to $102.6 billion depending on the method used, which decreased to $22.5-67.0 billion for 2019.These reductions are remarkable considering that the total cost of Medicare rose over the same period of time from $618.7 billion 11 to $799.4 billion 12 .Further, the cost reduction appears to be confined to fee-for-service since spending on Medicare Advantage plans in which coverage is maintained by private insurance companies changed little by comparison.
A detailed examination of Medicare spending by type of service indicates that while hospital inpatient costs decreased modestly (range: 8% to 21%), hospital outpatient costs dropped considerably more by 76-89% depending on the cost attribution method.In terms of absolute costs, hospital outpatient costs were about twice that of inpatient costs in 2014 but that ratio reversed itself in 2019 based on the first two methods.However, Part B providers, which in our categorization includes physician services, outpatient care not covered under the hospital outpatient category, freestanding ambulatory surgical centers, and a limited number of outpatient prescription drugs under certain conditions, increased by 36%.This category is the second or third highest in terms of cost of all the categories, depending on the method used.This data indicate that most wound care costs remain in the outpatient setting but have shifted from the hospital-based outpatient setting to the doctor's office (for example, a podiatrist or a physician with experience in wound care) but also away from the patient's home in terms of services.While this might naively imply that patients have shifted settings in the same proportions as cost, it is impossible to know exactly how many patients transferred from HOPDs to physician's offices.For example, in one interpretation the higher expenditures seen at physician's offices might be due to a modest rise in utilization of CTPs, while the much higher decrease in HOPD costs could have resulted from more expensive wound care treatments being largely curtailed.Large increases were also seen in DME (more than double), which might suggest that more (perhaps higher cost) dressings are being ordered for use in the patient's home.
We do not know the detailed causes for the shift in costs.However, there are a few factors that likely contributed, including CMS-initiated prior authorization programs for non-emergent indications 13 , especially hyperbaric indications 14 ; changes in the payment of CTPs, lack of access to CTPs for patients with larger wounds 15,16 ; and Medicare Advantage contracts that limit hospital facility fees.Finally, there is the ongoing shift towards value-based concepts and payment models in which CMS plays a key role in transitioning the health care system away from fee-for-service, which incentivizes quantity of care, and towards value-based care, which incentivizes high-quality care and smarter spending 17 .That said, there are no MIPS (Merit-Based Incentive Payment System) quality measures relevant to wounds or wound management nor does Medicare use any cost measures relevant to wound management There was a general decrease in expenditures for wounds per Medicate beneficiary with arterial ulcers decreasing the most, due to changes in the way it has been redefined by ICD-10 codes, followed by traumatic wounds, and surgical and diabetes infections.In contrast, cost expenditures for venous ulcers almost doubled while the most expensive wounds for 2019 were surgical wounds and pressure ulcers.
Prevalence rates for chronic medical conditions like a non-healing wound change over time for any of three reasons: first, the inability to effect a cure or prevent it from occurring which allows actual cases to increase with the population; second, an improvement in the ability to identify existing cases (cases undiagnosed in the population); and last, changes in the definition of the chronic condition which affects the way they are counted.The overall increase in wound prevalence was from 14.5% to 16.4%, which is relatively small.Comparable longitudinal studies are rare, and we found only one other study in the literature in which during a similar time in the UK, the 5-year change was 71% 18 .We think it unlikely that there has been a significant change in the ability to identify patients with chronic wounds so the movement from ICD-9 to ICD-10 is probably the biggest factor in the changing prevalence of certain types of wounds, such as the apparent increase in arterial ulcers (0.4% to 0.8%) and skin disorders (2.6% to 5.3%%).Unlike the codes specific to venous ulcers, there are no diagnosis codes specific to arterial ulcers.However, under ICD-10 it is now possible to indicate that a manifestation of atherosclerosis is ulceration.Thus, the apparent increase in certain wound types such as arterial ulcers might be due to the insights afforded by ICD10.The same is true for certain skin diseases.
Traumatic wounds decreased from 2.7% to 1.6% in general with consistently large decreases in all demographic groups.One possible explanation is that traumatic wounds were reclassified as chronic ulcers if they failed to heal in a timely fashion.However, as the prevalence of unclassified chronic ulcers did not change, this explanation seems unlikely.If coding changes to other wound types did take place, whether ICD-related or not, they are not obvious.Surgical wounds represent complications such as dehiscence, but not infections and these increased from 3.0% to 3.7%.However, we do not know if this represents a genuine increase in non-infection surgical complications or whether it can be explained by the volume increase in surgeries.The most noticeable trend, however, is the considerable increase in prevalence of all wound types for those under 65 years of age compared to other age groups, with the exception of traumatic wounds.A similar trend was noted in the UK study 18 .To be considered for Medicare if an individual is under 65 years of age, there must be a proven disability and for a high proportion of these patients who have a wound, the underlying cause of their disability could be a medical condition which also increases their risk of a chronic non-healing wound.Several studies have shown that in developed countries, a variety of comorbidities are increasing at an alarming rate in younger populations, including diabetes [19][20][21][22][23][24][25] .If this trend continues, the under-age 65 wound care population is likely to further increase relative to other age groups.
The outlook for patients with wounds based on our study findings in regard to treatment settings suggests that any ongoing access to care problems 26,27 could worsen because the population is ageing with a concurrent rise in the number of patients with diabetes, which will result in an increase in the cost of treating patients with chronic non-healing wounds.These patients need to be treated at multiple sites of services and if there are access issues, this makes appropriate treatment more challenging.
Our findings show that wound care costs have gone down substantially while the number of patients requiring wound care has increased.We submit that caution should be exercised by CMS when targeting any wound care services for additional spending cuts at any site or service, directly or indirectly since these policies would disproportionally impact patients with chronic wounds, particularly the disabled under 65.Patients receiving care at home are dependent on supplies such as dressings provided by DME suppliers (which are then applied by the patient or caregiver) or on skilled home health services and have nowhere else to go except to a skilled nursing facility or back to the acute care hospital.

Limitations of the study
A unique aspect of this study is that we did not make the a priori assumption that the spectrum of chronic wounds was largely determined by diabetic foot ulcers, venous leg ulcers, or pressure ulcers.Instead, we began with a comprehensive set of diagnosis codes from over 130 hospital-based outpatient departments to capture the types of conditions for which patients sought outpatient "wound" care.We then applied that comprehensive code set to Medicare claims data.Reviewers of our study were concerned that the change in ICD codes, amongst other differences in methods between the two time periods, could invalidate a comparison of the different time periods and this is a fair criticism.However, we did not find large or odd changes in most wound categories regarding prevalence, which most likely means the coding change did not affect these wounds, with some notable exceptions that we have highlighted, such as arterial ulcers.Had this not been the case the change in prevalence for all wound categories might have appeared somewhat anomalous.Second, although the costing methodology was broadly the same, we accept that there may be some uncertainty for 2014 expenditures because we estimated costs for the Medicare MA population whereas for 2019 data were based on the entire Medicare population.The overall sampling error for the 2014 dataset regarding prevalence (95% CI) was ±0.3% and a maximum variance in the total 2014 costs due to the method employed to estimate Medicare Advantage costs might be around ±14%, which is obtained by assuming a range of 14-42% of Medicare FFS spending for imputation of Medicare payments to MA plans (i.e.±50% of 28% figure used to impute the proportion of costs due to MA spending).It should also be noted that ICD-10 codes have still not solved the problem of correctly classifying wounds as diabetic foot ulcers or arterial ulcers and thus the possibility of undercounting them remains.Finally, in bundled payment settings, it is still difficult to determine the cost contribution of a chronic wound among many other often, overriding chronic conditions; wounds are often identified as secondary diagnoses.Our method of estimating costs based on three different sets of assumptions provides upper and lower bounds with the second method being reasonably conservative.

Conclusions
Our findings in comparing the prevalence of wounds for Medicare beneficiaries between 2014 and 2019 indicate that the number of individuals who have been treated for at least one wound is continuing to increase although diabetic foot ulcers, venous leg ulcers, and pressure ulcers are still less prevalent in the Medicare population compared to unclassified chronic ulcers and surgical wounds.Data suggest that younger adults with disabilities may be the most at risk of developing new wounds.Costs of wound care have substantially decreased with the biggest decrease observed for outpatient clinics.However, outpatient costs still represent the majority of spending on chronic wound care with costs shifts to the doctor's office and skilled nursing facilities.While a few explanations are offered, the reasons for all the cost changes cannot be known.Finally, it must be pointed out that Medicare spending on wound care is only a small part of the total cost of wound care in the U.S. when private insurance and patient out-of-pocket costs are included.Consequently, any national estimate of wound care costs, which would include individuals not in the Medicare programs, would significantly exceed these Medicare expenditures.

Declaration of funding
The Alliance of Wound Care Stakeholders funded the study.

Declaration of financial/other relationships
MJC is a paid consultant to the Alliance of Wound Care Stakeholders.JD, RH, MN, DC, and CEF have no financial or other relationships to declare.

Table 1 .
Notable differences in methodology between the 2014 and 2019 data analysis.

Table 2 .
Estimated number of Medicare beneficiaries with a wound: aggregate and by wound type (MA þ FFS) (thousands), ordered from largest to smallest (2019).
N/A: not available.

Table 3 .
Prevalence of wounds (%) in the Medicare population in 2014 and 2019 (bold) and by wound type and beneficiary demographics.Figures in parentheses represent prevalence of infections for types of wounds.Beneficiaries with multiple types of wounds are counted in each group.

Table 4 .
Medicare expenditure for wound care in 2014 and 2019 (bold) by wound type, in millions of U.S. dollars.

Table 5 .
Medicare expenditure for wound care by type of service in 2014 and 2019 (bold) in U.S. millions of dollars.Types of service are ordered by most to least expensive for the principal diagnosis for 2019.Figures in parentheses after each type of service indicate percentage of total Medicare FFS for 2019.DME: durable medical equipment; FFS: fee for service; HHA: home health agency; MA: Medicare Advantage; SNF: skilled nursing facility.

Table 6 .
Medicare spending for wound care per beneficiary (mean Values) in 2014 and 2019 (bold) by wound type, in U.S. dollars.
Wound types are ordered by most to least expensive for the principal diagnosis for 2019.