Diabetes-Related Amputations of Lower Extremities in the Medicare Population -- Minnesota, 1993-1995

Diabetes mellitus is the leading cause of nontraumatic lower-extremity amputations (LEAs) in the United States and accounts for 45%-70% of all nontraumatic LEAs (1,2). Approximately half of diabetes-related LEAs occur among persons aged greater than or equal to 65 years (1-3). To assess LEA hospitalization rates and costs for Medicare enrollees aged greater than or equal to 65 years with and without diabetes, the Minnesota Diabetes Control Program (DCP) and Stratis Health (Minnesota Medicare Quality Improvement Organization) analyzed data for federal fiscal years 1993-1995 (October 1992-September 1995). This report summarizes the findings, which indicate that the LEA Medicare hospitalization rate for persons with diabetes was nearly 13 times the rate for persons without diabetes.

International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM), procedural codes 84.10-84.19 were used to identify LEAs in inpatient claims data. Trauma-related LEAs (codes 895-897) were excluded from the analyses. Medicare enrollees who participated in capitated risk health-maintenance organization (HMO) plans (approximately 10%) were excluded because no claims were available describing their care. Persons with diabetes were identified by a discharge code of 250.0-250.9 listed at the time of the LEA or during any hospitalization within the preceding 365 days. Diabetes prevalence estimates and confidence intervals (CIs) were the average annual state prevalence estimates and CIs of diabetes derived from the Behavioral Risk Factor Surveillance System for 1993-1995. These prevalence estimates were applied to the Minnesota Medicare population (derived from the Medicare enrollment history files) to estimate the number of persons with and without diabetes in this population. LEA hospitalization rates were calculated per 10,000 Medicare enrollees with or without diabetes by age and sex. Relative risk was defined as the hospitalization rate for LEA among persons with diabetes divided by the rate among persons without diabetes. The population attributable risk (PAR) was calculated by subtracting the LEA hospitalization rate for persons without diabetes from the rate for the total population, and dividing by the total population rate (4).

The average annual number of LEA hospitalizations was 931 (Table_1); of these, 552 (59%) occurred among persons with diabetes. The average annual cost to Medicare for LEA hospitalizations in Minnesota was $10.2 million, $6 million of which was for persons with diabetes.

Regardless of diabetes status, the LEA hospitalization rates (per 10,000 Medicare enrollees) were higher for men than for women and for persons aged greater than or equal to 75 years than for persons aged 65-74 years. The relative risk for LEA hospitalization among persons with diabetes compared with persons without diabetes was 12.7 per 10,000 Medicare enrollees (95% CI=10.9-14.9). For persons with diabetes compared with persons without diabetes, the relative risk was higher for men (14.2; 95% CI=11.2-19.0) than women (10.8; 95% CI=9.0-13.1) and higher for persons aged 65-74 years (23.5; 95% CI=19.3-29.1) than persons aged greater than or equal to 75 years (8.6; 95% CI=7.0-11.0). On the basis of PAR calculations, 55% of all hospitalizations for LEA were directly attributable to diabetes.

The Minnesota DCP and Stratis Health are collaborating to define the burden of diabetes in the elderly population. These data will be incorporated into continuous quality-improvement programs conducted by Stratis Health for the Medicare population in Minnesota. The Minnesota Department of Health will analyze these data by county to help identify areas in which interventions are needed.

Reported by: D Gilbertson, PhD, T Arneson, MD, Stratis Health, Minneapolis; J Desai, J Roesler, MPH, J Bluhm, MPH, C Clark, MA, D Bishop, PhD, Minnesota Dept of Health. Epidemiology and Statistics Br, Div of Diabetes Translation, National Center for Chronic Disease Prevention and Health Promotion, CDC.

Editorial Note

Editorial Note: The diabetes-related lower extremity conditions that increase the risk for amputation among persons with diabetes include peripheral neuropathy, peripheral vascular disease, and infection (5). Peripheral neuropathy may cause loss of sensation in feet, resulting in a patient's failure to perceive foot problems and may cause development of foot deformities that increase pressure points susceptible to ulceration. Osteomyelitis and gangrene may develop from inadequate blood supply and infection. Risk factors for amputation include being older, male, a member of certain racial/ethnic groups, having poor glycemic control, having diabetes for a longer period, and practicing or receiving poor preventive health care (1).

The findings in this report indicate that, in Minnesota, approximately half of all hospitalizations for LEA were attributable directly to diabetes. Many of these amputations may have been preventable. Preventive foot-care programs for persons with diabetes can decrease the incidence of LEAs or serious foot conditions leading to LEA by 44%-85% (3). Such programs emphasize foot-care education for persons with diabetes, their families, and their physicians; preventive foot-care practices (e.g., proper footwear and foot hygiene); early detection of foot conditions through frequent foot examinations by patients and physicians; teamwork among health-care providers in different disciplines; and appropriate treatment and follow up (6-8). Recent clinical trials found that good control of blood sugar levels among persons with type 1 or type 2 diabetes can reduce or delay development of peripheral neuropathy, a major precursor of amputation (7,8).

The findings in this report are subject to at least four limitations. First, data were not available for the Medicare enrollees who participated in capitated risk HMO plans. Second, this analysis only included Medicare claims for hospital inpatient care and did not include claims for hospital outpatient care (part

1. or claims for physicians (part B), which would enable determination of diabetic status or LEAs performed in an ambulatory setting. Third, numerator data that relied on ICD-9 coding may have contained some inaccuracies. Finally, denominator data relied on estimates of self-reported diabetes status. However, these LEA surveillance data from Minnesota are consistent with those from other studies and are comparable with national data (1-3,9). For example, the average LEA hospitalization rates per 1000 persons with diabetes in the Minnesota Medicare population for 1993-1995 were 9.9 for persons aged 65-74 years and 11.0 for persons aged greater than or equal to 75 years, compared with hospitalization rates for the U.S. population in 1994 of 10.2 for persons aged 65-74 years and 11.9 for persons aged greater than or equal to 75 years.

A national health objective for 2000 is to decrease diabetes-related amputation rates by 40% (from 8.2 to 4.9 per 1000 persons with diabetes) (10). CDC is providing assistance to state DCPs for surveillance of diabetes, identification of areas for intervention, and implementation and evaluation of those interventions. Continued collaboration among health-care providers, public health officials, members of community-based organizations, and patients will be necessary to reduce LEAs among patients with diabetes.

References

1. Reiber GE, Boyko EJ, Smith DG. Lower extremity foot ulcers and amputations in diabetes. In: Harris MI, Cowie CC, Stern MP, et al, eds. Diabetes in America. 2nd ed. Washington, DC: US Department of Health and Human Services, Public Health Service, National Institutes of Health, 1995; DHHS publication no.(NIH)95-1468.

2. Most RS, Sinnock P. The epidemiology of lower extremity amputations in diabetic individuals. Diabetes Care 1983;6:87-91.

3. Bild DE, Selby JV, Sinnock P, Browner WS, Braveman P, Showstack JA. Lower-extremity amputation in people with diabetes: epidemiology and prevention. Diabetes Care 1989;12:24-31.

4. Kleinbaum DG, Kupper LL, Morgenstern H. Epidemiologic research: principles and quantitative methods. New York, New York: Van Nostrand Reinhold, 1982:161.

5. CDC. The prevention and treatment of complications of diabetes mellitus: guide for primary care practitioners. Atlanta, Georgia: US Department of Health and Human Services, Public Health Service, 1991.

6. American Diabetes Association. Standards of medical care for patients with diabetes mellitus. Diabetes Care 1998;21(suppl 1):S54-S55.

7. The Diabetes Control and Complications Trial Research Group. The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus. N Engl J Med 1993;329:977-86.

8. Ohkubo Y, Kishikawa H, Araki E, et al. Intensive insulin therapy prevents the progression of diabetic microvascular complications in Japanese patients with non-insulin-dependent diabetes mellitus: a randomized prospective 6-year study. Diabetes Res Clin Pract 1995;28:103-17.

9. CDC. Diabetes surveillance, 1997. Atlanta, Georgia: US Department of Health and Human Ser-vices, Public Health Service, 1998 (in press).

10. Public Health Service. Healthy people 2000: national health promotion and disease prevention objectives--full report, with commentary. Washington, DC: US Department of Health and Human Services, Public Health Service, 1991; DHHS publication no. (PHS)91-50212.

TABLE 1. Prevalence* of and average reimbursement for lower extremity amputations
(LEAs)+ among persons with and without diabetes -- Minnesota Medicare population,
October 1993-September 1995
==========================================================================================
                               No.                                            Average
Characteristics          hospitalizations    Rate&        (95% CI)        reimbursement@
----------------------------------------------------------------------------------------
Persons with diabetes
 Sex
  Men                          324           144.4        (117.3-187.9)       $10,631
  Women                        228            75.4        ( 64.6- 90.7)       $11,112
 Age group (yrs)
  65-74                        258            98.6        ( 82.8-122.1)       $11,184
  >=75                         294           110.5        ( 92.1-138.1)       $10,511

 Total                         552           105.6        ( 93.0-122.2)       $10,829

Persons without
 diabetes
 Sex
  Men                          190            10.2        (  9.9- 10.5)       $11,215
  Women                        189             7.0        (  6.9-  7.2)       $10,859
 Age group (yrs)
  65-74                        101             4.2        (  4.2-  4.2)       $12,860
   >=75                        278            12.9        ( 12.6- 13.2)       $10,372

  Total                        379             8.3        (  8.2-  8.5)       $11,037

Total                          931            18.3                            $10,914
---------------------------------------------------------------------------------------
* Annual averages for fiscal year 1993 through fiscal year 1995.
+ For inpatient procedures only.
& Per 10,000 Medicare enrollees with or without diabetes.
@ Average Medicare reimbursements for LEA hospitalizations.
==========================================================================================

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