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Data Points Publication Series [Internet]. Rockville (MD): Agency for Healthcare Research and Quality (US); 2011-.

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Incidence of diabetic foot ulcer and lower extremity amputation among Medicare beneficiaries, 2006 to 2008

Data Points #2

, MD, PhD, , DPM, MSCE, , MA, , PharmD, , PhD, , PhD, , BA, , BA, and , PT, MA.

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In Medicare Parts A and B fee-for-service beneficiaries with diabetes, the incidence of diabetic foot ulcer is about 6.0% and lower extremity amputation about 0.5%.

Among Medicare Parts A and B fee-for-service beneficiaries with diabetes and foot ulcer, the prevalence of microvascular and macrovascular complications is about 46% and 65%, respectively. Further, among those with a lower extremity amputation, the prevalence of microvascular and macrovascular complications is about 46% and 76%, respectively.

The annual mortality rate for Medicare Parts A and B fee-for-service beneficiaries with diabetes who have an incident diabetic foot ulcer is about 11%; for those with an incident lower extremity amputation, about 22%.

Diabetes mellitus, a metabolic disorder characterized by elevated blood glucose, is a serious and growing problem. More than 23 million people in the United States (U.S.) are believed to have diabetes. It is estimated that by 2025, 300 million people worldwide will have diabetes and by 2030, 360 million people. Thus, by 2030, world-wide prevalence will approach 5 percent.1–4

In general, the incidence of nontraumatic lower extremity amputations (LEAs) has been reported to be at least 15 times greater in those with diabetes than with any other concomitant medical illness.3;5;6 It has been reported that annually, about 1 to 4 percent of those with diabetes develop a foot ulcer; 10 to 15 percent of those with diabetes will have at least one foot ulcer during their lifetime.7

LEA is less common but is an extreme complication associated with diabetes and foot ulcer. In the U.S., nearly 80,000 LEAs are performed on diabetics each year.8;9 In 2005, the overall rate of hospital discharge for new LEA was about 4.3 per 1,000 people with diabetes compared with a rate of about 0.3 per 1,000 in the general population.4;8;10–13

In 2003, the Centers for Disease Control and Prevention’s (CDC’s) National Hospital Discharge Survey (www.cdc.gov/nchs/nhds.htm; data available at www.cdc.gov/diabetes/statistics/hospitalization_national.htm) reported a rate of 8 hospital discharges with a diagnosis of foot ulcer per 1,000 individuals with diabetes ages 65–74. Among patients with diabetes age 75 and over, the rate was 11 per 1,000. These data are limited because they did not include outpatient care or chronic care facilities, may have counted individuals who had venous leg ulcers, and may have counted individuals more than once if they were hospitalized more than once. Using the same dataset, the CDC estimated that the rate of LEA in 2005 was 5.3 to 5.6 per hospital discharge per 1,000 individuals with diabetes. These rates have been shown to exhibit variation by age, gender, race/ethnicity, and Dartmouth Atlas of Health Care Hospital Referral Region (HRR, www.dartmouthatlas.org).14

People with diabetes often experience several associated medical complications, such as renal disease, cardiac disease, and retinopathy. These complications are often categorized as microvascular (e.g., nephropathy, retinopathy) and macrovascular (e.g., cardiac disease). Many researchers have reported an increased incidence of death among LEA patients. Depending on the study, the 1-year post-LEA mortality rate in people with diabetes is between 10 and 50 percent, and the 5-year mortaity rate post-LEA is between 30 and 80 percent.15–17

This Data Points brief explores the incidence of foot ulcer and LEA in Medicare beneficiaries. Incidence is the number of new onsets of an illness in a specified period of time. This is distinct from prevalence, the number of people affected by an illness during a period of time. While both incidence and prevalence are important for public health decisions, the former more clearly describes the impact of a new onset of an illness, can help determine if prevention methods are successful, is useful when trying to determine risk factors for the onset of a new disease, and can be used to help gauge the severity of illness. This Data Points also examines microvascular and macrovascular complications associated with diabetes, as well as the death rate among people with diabetic foot ulcer and LEA. Refer to companion briefs for separate discussions of the prevalence of diabetes, foot ulcer, and LEA; and medical utilization and costs associated with foot ulcers and amputation.

FINDINGS

Incidence of Foot Ulcer

Among Medicare beneficiaries continuously enrolled for at least 12 months in Parts A and B fee-for-service (FFS), continuously enrolled for each calendar year of interest (hereafter referred to as the Medicare Parts A and B FFS population; see Data Source section for a comprehensive definition), and with diabetes, the annual incidence of diabetic foot ulcer was 6.0 percent in 2006, 2007, and 2008 (Table 1).

Table 1. Yearly Incidence of Diabetic Foot Ulcer and LEA in Medicare FFS Beneficiaries (Parts A and B), 2006–2008.

Table 1

Yearly Incidence of Diabetic Foot Ulcer and LEA in Medicare FFS Beneficiaries (Parts A and B), 2006–2008.

The incidence of diabetic foot ulcer in the Medicare FFS subpopulation with diabetes and peripheral arterial disease (PAD) was more than two times greater, with incidence rates of 13.5 percent in 2006, 13.2 percent in 2007, and 13.1 percent in 2008.

Foot ulcer rates varied by age, gender, race/ethnicity, and geographic location. For example, in 2008, the annual incidence of foot ulcer among those with diabetes was 6.0 percent for males and 5.9 percent for females. The annual incidence of foot ulcer among beneficiaries with diabetes by race in 2008 was white, 6.0 percent; African American, 6.3 percent; Asian, 3.4 percent; Hispanic, 6.4 percent; American Indian/Alaska Native, 7.0 percent; and other, 4.0 percent. Geographic distribution of incident foot ulcer among those with diabetes varied widely based on Dartmouth Atlas of Health Care HRRs. However, the yearly incidence rates varied little from 2006 to 2008.

Incidence of LEA

Among Medicare Parts A and B FFS beneficiaries with diabetes, the annual incidence of LEA was 0.5 percent in 2006 and 2007 and 0.4 percent in 2008 (Table 1). The annual incidence of LEA in the Medicare FFS subpopulation with diabetes and PAD was about four times as high as the incidence in the diabetic Medicare FFS population, with a yearly incidence of 2.1 percent in 2006, 1.9 percent in 2007, and 1.8 percent in 2008. However, incidence appears to be trending down.

Incidence varied by age, gender, race/ethnicity, and geographic location. For example, in 2008, the annual incidence of LEA in the Medicare FFS population with diabetes was 0.6 percent for males and 0.3 percent for females. The annual incidence of LEA among Medicare FFS beneficiaries with diabetes by race was white, 0.4 percent; African American, 0.7 percent; Asian, 0.2 percent; Hispanic, 0.5 percent; American Indian/Alaska Native, 0.8 percent; and other, 0.4 percent. Geographic distribution of incident LEA among those with diabetes varied widely based on the Dartmouth Atlas of Health Care HRRs (Figure 1).

U.S. maps showing distribution of lower extremity amputation rates in 2006, 2007, and 2008. In 2006, rates ranged from 0.16 to 0.89. Rates were highest in the South. In 2007, rates ranged from 0.19 to 0.79 and were highest in the Northwest and the South. In 2008, rates ranged from 0.24 to 0.79 and were highest in the South, the East Coast, and Alaska.

Figure 1

Annual incidence of LEA (nonadjusted) per 100 Medicare FFS beneficiaries (Parts A and B) based on Dartmouth Atlas of Health Care Hospital Referral Regions (HRRs), 2006–2008.

Geographic variation was also affected by gender, age, race/ethnicity, as well as the presence of microvascular complications, macrovascular complications, and obesity (Figure 2, as an example for 2007).

U.S. maps showing distribution of lower extremity amputation rates in 2007, adjusted and nonadjusted. For nonadjusted, rates ranged from 0.19 to 0.79. Rates were highest in the South and Northwest. For adjustment using basic specification (age, gender, race/ethnicity), rates ranged from 0.21 to 0.83 and were highest in the Northwest and the South. For adjustment using expanded specification (basic plus obesity, microvascular and macrovascular conditions, and HRR), rates ranged from 0.23 to 1.07 and were highest in the Southeast, North Central, and Northwest areas.

Figure 2

Annual incidence of LEA per 100 Medicare FFS beneficiaries (Parts A and B) Based on Dartmouth Atlas of Health Care Hospital Referral Regions, 2007.

Other factors also affected the incidence rate of LEA. As expected, those with a prevalent foot ulcer were more likely to have an incident LEA. But the annual incidence of LEA among Medicare FFS beneficiaries with a prevalent diabetic foot ulcer trended downward. Incidence was 5.3 percent in 2006, 5.0 percent in 2007, and 4.9 percent in 2008. This finding may be reflected in the rate of osteomyelitis in those with a diabetic foot ulcer, which was 13.2 percent in 2006 and 2007 and 13.6 percent in 2008 and has been shown to be a risk factor for LEA. The annual incidence of amputation among those with a previous incident amputation was 16.7 percent in 2006, 17.5 percent in 2007, and 17.1 percent in 2008.

Individuals with diabetic foot ulcers and LEAs often have other complications associated with diabetes. Among those with diabetic foot ulcers, the prevalence of microvascular complications was 45.8 percent in 2006, 46.7 percent in 2007, and 47.6 percent in 2008. Among those with diabetic foot ulcers, the prevalence of macrovascular complications was 65.9 percent in 2006, 65.4 percent in 2007, and 65.0 percent in 2008.

Mortality

The rate of death among diabetic Medicare FFS beneficiaries with a prevalent diabetic foot ulcer was 12.7 percent in 2006, 12.4 percent in 2007, and 12.3 percent in 2008. The rate of death among diabetic Medicare FFS beneficiaries with an incident diabetic foot ulcer (i.e., a new foot ulcer in the same year, but before their death) was 11.1 percent in 2006, 10.9 percent in 2007 (Table 2), and 10.7 percent in 2008. Mortality after a prevalent LEA was 18.2 percent in 2006, 17.5 percent in 2007, and 17.0 percent in 2008. Mortality after an incident LEA was 23.1 percent in 2006, 21.8 percent in 2007 (Table 2), and 20.6 percent in 2008.

Table 2. Yearly mortality rate (per 100) for diabetes, incident diabetic foot ulcer, and incident LEA, in diabetic Medicare FFS beneficiaries (Parts A and B), 2007.

Table 2

Yearly mortality rate (per 100) for diabetes, incident diabetic foot ulcer, and incident LEA, in diabetic Medicare FFS beneficiaries (Parts A and B), 2007.

DATA SOURCE

Unless otherwise specified, the prevalence and incidence rates in this Data Points brief were derived from the Medicare Parts A and B FFS population. Prevalence and incidence was determined separately for 2006, 2007, and 2008. A beneficiary was included in the enrollment population for a given year if he or she had at least a 12-month period of continuous Parts A and B FFS enrollment centering on any one of the months in a given year and was continuously enrolled in the given year. It is important to note that beneficiaries were considered continuously enrolled for 12 months, centered on a given month, if they were alive in that given month and were continuously enrolled up until death. For this purpose, beneficiaries were considered alive up to and including the month of their death. Continuous enrollment in the given year was not required for analyses of quarterly and monthly incidences. Enrollment was determined using the Medicare Enrollment Database (EDB).

ADDITIONAL FINDINGS AVAILABLE ONLINE

The following additional materials are available online at http://www.effectivehealthcare.ahrq.gov/index.cfm/search-for-guides-reviews-and-reports/?pageaction=displayproduct&productid=627.

Annual Incidence of Foot Ulcer Among Diabetic Medicare Parts A and B FFS Beneficiaries, 2006–2008 (MS Excel, 37K)

Annual Incidence of LEA Among Diabetic Medicare Parts A and B FFS Beneficiaries, 2006–2008 (MS Excel, 37K)

Quarterly Incidence of Foot Ulcer Among Diabetic Medicare Parts A and B FFS Beneficiaries, 2006–2008 (MS Excel, 38K)

Quarterly Incidence of LEA Among Diabetic Medicare Parts A and B FFS Beneficiaries, 2006–2008 (MS Excel, 39K)

Monthly Incidence of Foot Ulcer Among Diabetic Medicare Parts A and B FFS Beneficiaries, 2006–2008 (MS Excel, 47K)

Monthly Incidence of LEA Among Diabetic Medicare Parts A and B FFS Beneficiaries, 2006–2008 (MS Excel, 47K)

Annual Incidence of LEA Among Diabetic Medicare Parts A and B FFS Beneficiaries With Prevalent Foot Ulcer, 2006–2008 (MS Excel, 35K)

Mortality Rates in Diabetic Medicare Parts A and B FFS Population, Diabetic Foot Ulcer Prevalent Population, and Diabetic Foot Ulcer Incident Population, 2006–2008 (MS Excel, 38K)

Mortality Rates in Diabetic Medicare Parts A and B FFS Population, LEA Prevalent Population, and LEA Incident Population, 2006–2008 (MS Excel, 38K)

Annual Prevalence of Osteomyelitis Among Diabetic Medicare Parts A and B FFS Beneficiaries With and Without Foot Ulcer, 2006–2008 (MS Excel, 36K)

Annual Prevalence of Micro- and Macrovascular Complications Among Diabetic Medicare Parts A and B FFS Beneficiaries With and Without Foot Ulcer, 2006–2008 (MS Excel, 41K)

Annual Prevalence of Micro- and Macrovascular Complications Among Diabetic Medicare Parts A and B FFS Beneficiaries With and Without LEA, 2006–2008 (MS Excel, 41K)

DEFINITIONS AND METHODOLOGY

Definition and Prevalence of Diabetes

Individuals were determined to have diabetes if they had two or more claims with International Classification of Diseases, 9th Revision (ICD-9) codes consistent with diabetes or at least one inpatient claim with ICD-9 codes consistent with diabetes (250.00–03, 250.10–13, 250.20–23, 250.30–33, 250.40–43, 250.50–53, 250.60–63, 250.70–73, 250.80–83, 250.90–93) in the 12-month period of continuous enrollment. Gender, race/ethnicity, and age were all extracted from the EDB. Geographic distribution of diabetes prevalence varied widely based on Dartmouth Atlas of Health Care HRRs (www.dartmouthatlas.org) but little by year, as presented in Figures 1 and 2.

Definition and Incidence of Foot Ulcer

Beneficiaries with diabetes, as defined above, were considered to have an incident foot ulcer if they had a primary or secondary (i.e., nonprimary) diagnosis of foot ulcer during any given year (based on the following ICD-9 codes: 681.9, 682.7, 707.10, 707.13, 707.14, 707.15, 707.8, 707.9, 730.06–09, 730.16, 730.19,730.26–29, 891.0, 891.1,891.2, 892.0, 892.1, 892.2), but had at least a preceding 6-month period of none of these codes. Any beneficiary with diabetes and a venous leg ulcer code (454.0, 454.1, 454.2, 454.9) was not defined as having a foot ulcer and was excluded. Incidence was calculated by dividing the number of beneficiaries identified with diabetes and an incident foot ulcer for the given year by the number of beneficiaries in the Medicare FFS population who were continuously enrolled in Parts A and B throughout the given year and identified with diabetes for that year.

Definition and Incidence of Lower Extremity Amputation

Beneficiaries with diabetes, as defined above, for any given year were defined as having an incident LEA if they had any of a group of specific Current Procedural Terminology (CPT) codes (27590, 27591, 27592, 27594, 27596, 27598, 27880, 27881, 27882, 27884, 27886, 27888, 27889, 28800, 28805, 28810, 28820, 28825), ICD-9 procedure codes (84.10–17, 84.3), or ICD-9 diagnosis codes (895.0, 895.1, 896.0–3, 897.0–7, V497.0–6) and a previous 6-month period without any of these CPT codes or ICD-9 codes. Incidence was calculated by dividing the number of beneficiaries identified with diabetes and an incident LEA by the number of beneficiaries in the Medicare FFS population who were continuously enrolled in Parts A and B FFS throughout the given year and were identified with diabetes for that year.

Definition of Macro- and Microvascular Disease

Beneficiaries with diabetes and prevalent diabetic foot ulcer or LEA, as defined above, were defined as having macrovascular complications if they had a primary or secondary (i.e., nonprimary) diagnosis based on the following ICD-9 codes: 250.70–73, 410.00–.02, 410.10–12, 410.20–22, 410.30–.32, 410.40–42, 410.50–52, 410.70–72, 410.80–82, 410.90–92, 413.9, 428.0., 428.1, 428.9, 430, 431, 432.1, 432.9, 434.00, 434.01, 434.10, 434.11, 434.90, 434.91, 435.1–435.3, 435.8, 435.9, 436, 437.1–9, 438.10–12, 438.19–22, 438.30–32, 434.40–42, 438.50–53, 438.6, 438.7, 438.81–85, 438.89, 438.9. Beneficiaries were defined as having microvascular complications if they had a primary or secondary diagnosis based on the following ICD-9 codes: 250.40–43, 250.50–53, 250.60–63. The former set of ICD-9 codes represents the following macrovascular diseases: peripheral arterial disease, myocardial infarction, heart failure, angina, and cerebrovascular disease. The latter set of ICD-9 codes represents the following microvascular diseases: diabetic renal disease, diabetic ophthalmic disease, and diabetic neurologic disease.

Mortality

Annual mortality was calculated separately for each relevant population (e.g., the prevalent diabetic foot ulcer subpopulation of Medicare FFS beneficiaries as previously defined). For each population, the numerator was the number of beneficiaries within the particular population who died in the given year, and the denominator was the total number of beneficiaries in the population of analysis. Beneficiary death dates were obtained from the EDB.

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Acknowledgments

The authors wish to thank David Hsia for his critical review of this brief, Mary A. Leonard and Doreen Bonnett for their graphic design expertise, and Edmund Weisberg for his medical editing expertise.

This project was funded under Contract No. HHSA29020050041I from the Agency for Healthcare Research and Quality, U.S. Department of Health and Human Services as part of the Developing Evidence to Inform Decisions about Effectiveness (DEcIDE) program. The authors of this report are responsible for its content. Statements in the report should not be construed as endorsement by the Agency for Healthcare Research and Quality or the U.S. Department of Health and Human Services.

Suggested Citation: Margolis D, Malay DS, Hoffstad OJ, et al. Incidence of diabetic foot ulcer and lower extremity amputation among Medicare beneficiaries, 2006 to 2008. Data Points #2 (prepared by the University of Pennsylvania DEcIDE Center, under Contract No. HHSA29020050041I). Rockville, MD: Agency for Healthcare Research and Quality. January 2011. AHRQ Publication No. 10(11)-EHC009-1-EF.

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