Diabetic patients who have undergone a lower extremity amputation are more likely to die than patients who have not undergone an amputation, according a study recently published in Diabetes Care. However, the study failed to find a reason for this correlation.
David J. Margolis, MD, PhD, professor of Dermatology at Perelman School of Medicine, and colleagues examined a cohort of patients whose care was recorded in The Health Improvement Network (THIN), a data source that collects primary medical care information from electronic medical records in the United Kingdom. Past studies conducted by Margolis and colleagues had shown that patients with diabetes and a lower extremity amputation (LEA) are two to three times more likely to die at any point in time than those with diabetes who have not undergone an LEA.
Searching for a cause of death
“We had realized from a couple of studies we had done in the past that patients who had lower extremity amputations and lower extremity ulcers were more likely to die than those who did not [have LEA or ulcers]. And we thought that maybe there was a possibility of looking at the patient records to see why they were in fact dying,” Margolis told O&P News.
The researchers hypothesized a correlation between the higher rates of death and diabetic complications, such as cardiovascular disease and renal failure. The risk factors included in the study were selected due to their known association with the most frequent causes of death in people with diabetes.
Between 2003 and 2012, 416,434 patients met the entrance criteria for the study, which included having diabetes and at least 1-year follow up and being at least 25 years of age at the time of diagnosis with diabetes. Among those patients, 6,566 (1.6%) patients had an LEA and 77,215 (18.5%) patients died. Almost all risk factors were statistically significantly different for patients who had an LEA in comparison with those who did not, as well as those who died compared with patients who did not. In general, patients with an LEA were more than three times more likely to die within 1 year of follow-up than those who did not have an LEA.
Margolis and colleagues were surprised to find that adjusting patient statistics for risk factors did not reduce their risk of death.
“We thought we would look at those who had an LEA and adjust away at least medical visits for cardiovascular events and thought that the increased risk [of death] would go away, but it did not,” Margolis said. “It barely went away at all after we adjusted for those things. Our conclusion was that we could not explain why individuals with amputations were more likely to die than individuals who did not have amputations.”
Increased risk of death could not be primarily explained by myocardial infarction, chronic kidney disease, cerebrovascular accident, congestive heart failure, peripheral vascular disease/arterial insufficiency or the Charleston morbidity index.
“We do not completely understand what it means,” Margolis said.
The only correlation found was between death and LEA, but this does not make sense since “amputation is a procedure and people are not dying after the procedure itself. People are dying well after the procedure is completed and the patient is healed,” he said.
Sensitivity analysis showed the existence of an “unmeasured cofounder” – in other words, a physical cause that was not considered – is unlikely to exist.
The results point to a need for better monitoring of patients with diabetes and LEA, he said.
“One of the things [the results] may mean is that individuals who have amputations maybe are – both the patients and providers – more concerned about their amputations and are not spending time with their other medical problems,” Margolis said. This could lead to risks like heart disease going undiagnosed or being under-cared for, he said. “Or it could be … that maybe individuals who have severe enough [diabetes] to have amputation, have other medical problems we just do not fully understand.”
Further studies are warranted to better determine possible causes for the increased risk of death in patients with LEA, Margolis said.
“I think one of the things that certainly could be further researched is to try to follow these individuals more closely and measure other health qualities … better understand their glucose control, better understand if maybe they are having silent heart attacks or thing that are going undocumented by the physicians,” he said.
Researchers also could investigate whether patients are complying fully with medical care recommendations.
“It could certainly be that … patients who have had amputations may be more depressed and may be less eager to do other things because they already think there is some finality to their amputation and their inability to heal,” Margolis said.
“The bottom line is that perhaps we need to be, as health care providers, more vigilant in terms of caring for these individuals.” – by Amanda Alexander
- Margolis DJ, et al. Diabetes Care. 2015;doi:10.2337/dc15/0536.
Disclosure: Margolis reports no relevant financial disclosures.