Published 8/1/2010
Jennie McKee

Examining differences in diabetic foot amputation

Research finds more amputations in males and higher mortality in women

“Diabetes has tremendous economic, societal, and personal costs,” said Monica Peek, MD, MPH, “most of which result from microvascular and macrovascular complications, such as retinopathy, nephropathy, and lower extremity amputations (LEA).”

According to Dr. Peek, studies of avoidable hospitalizations for diabetes-related LEA have found consistent patterns of differences between the sexes. The data have shown that, despite equivalent hospitalization rates for uncontrolled diabetes, men are considerably more likely to undergo amputation than women. When women do undergo amputation, she said, they have higher mortality rates associated with the procedure than men.

Although the underlying reasons for these differences are unknown, she said, “biologic factors—including increased rates of peripheral vascular disease and peripheral neuropathy in men, and cardiac disease in women—appear to contribute.”

Dr. Peek, an assistant professor in the division of general internal medicine at the University of Chicago, is a researcher in the area of healthcare disparities related to diabetes. She participated in the recent research symposium on Musculoskeletal Health Care Disparities sponsored by the AAOS, the Orthopaedic Research Society, and the American Bone and Joint Surgeons.

Amputation rates
Dr. Peek noted that a 2006 study based on data from the Agency for Healthcare Research and Quality’s Medical Expenditure Panel Survey, as well as its Healthcare Cost and Utilization Project, found a rate of 55 LEAs in male diabetes patients (per 100,000 population) compared to 28 LEAs in women with diabetes.

The study also found that differences between men and women persist across different racial and ethnic groups (Fig. 1) and that male patients are younger than female patients at the time of LEA.

“We know that men are more likely to have some of the independent predictors for LEA,” she noted, emphasizing that peripheral neuropathy may have a particularly important influence on varying rates of LEA among male and female patients.

Differences in biomechanics between men and women—specifically, decreased joint mobility and higher foot pressures—may predict the development of diabetic foot ulcers. According to a 2008 study, male patients had less joint mobility and higher foot pressures than females.

The study found that women had similar odds as men of diabetes-related foot ulcers developing if the women had equivalent measures of neuropathy, joint mobility, and foot pressures as the male patients.

“Men with diabetes have nearly twice the odds of having insensate neuropathy as women with diabetes. They also have nerve conduction abnormalities that are more severe,” she said.

A possible reason for increased insensate neuropathy among men, said Dr. Peek, may be related to greater height in men.

“Insensate neuropathy is partially determined by peripheral nerve length, which is a function of height,” she explained, noting that one study found that the effect of height was entirely responsible for increased odds of sensory neuropathy in men.

Differences in mortality
According to Dr. Peek, data point to women having higher mortality rates associated with diabetes-related LEA. In a 1997 study of operative and perioperative mortality associated with diabetes-related LEA, women had 37.7 deaths per 1,000 amputations, while males had 29.7 deaths per 1,000 amputations. In addition, more deaths were found among female whites and Hispanic patients than among male whites and Hispanics, but no significant difference was found when comparing male and female African-Americans (
Fig. 2).

Another 1997 study reported risk factors associated with in-hospital mortality and the need for institutional care in diabetic patients who underwent LEA. Based on data for LEA-related hospitalizations in six metropolitan statistical areas in South Texas, researchers found a strong association between death following LEA and factors such as female sex, high level amputation, advanced renal disease, anemia, and congestive heart failure.

Dr. Peek said that higher rates of cardiovascular deaths among women after LEA may account for differences in mortality rates between the sexes. According to the literature, women with diabetes may be at an increased risk of atherosclerotic complications compared to men with diabetes.

Is care equal?
Healthcare factors do not appear to play a role in differences among men and women who undergo LEA, stated Dr. Peek. Evidence exists that men receive equal or higher quality diabetes-related care, including more foot examinations by healthcare providers.

“In addition,” she said, “evidence indicates that prior gender differences in diabetes foot self-care have resolved.”

In 2000, she noted, the age-adjusted prevalence rates of foot self-exams were 7 percent lower for men than women (58.5 percent versus 65.8 percent, respectively). By 2007, however, the rates were measured at 65.8 percent for both genders, according to national data from the Behavioral Risk Factor Surveillance Study.

More study needed
Dr. Peek called for more research to confirm the differences between men and women concerning diabetes-related LEA mortality. She also urged researchers to explore underlying mechanisms for differences in rates of amputation and mortality between the sexes.

“Biologic factors appear to contribute to these differences, but more research in this area is warranted,” she said. “Physicians will not be able to make strides in addressing these differences until we gain a better understanding of them.”

Disclosure information: Dr. Peek—Robert Wood Johnson Foundation Harold Amos Medical Faculty Development Program and the Mentored Patient-Oriented Career Development Award of the National Institute of Diabetes and Digestive and Kidney Diseases.

Jennie McKee is a staff writer for AAOS Now. She can be reached at mckee@aaos.org


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