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Heartline Magazine January - March 2005
Amputations in Barbadians with diabetes
By Anselm Hennis MRCP (UK), Ph.D
Senior Lecturer, Chronic Disease Research Centre, Tropical
Medicine Research Institute, UWI and Consultant Physician, Queen Elizabeth
Hospital
Diabetes affects is a major cause of morbidity and mortality
in the Caribbean and affects 10% of adults. Global projections are for the rates
of diabetes to continue to rise and most of the new cases will arise in
developing middle-income communities such as ours. Complications such as
diabetes-related foot disease and lower limb amputations are believed to be very
common, and reports published in the late 1980s indicated that as many as 80% of
female surgical beds at the Queen Elizabeth Hospital were occupied by women
suffering from these conditions. The true extent of the problem had however, not
previously been quantitatively evaluated or specific risk factors for lower limb
amputation identified locally. In order to guide clinical best practice and
inform public health policy it is critical to document the scope of problems
relevant to our community. We therefore embarked on a collaboration with
Professor Nish Chaturvedi of the National Heart and Lung Institute, Imperial
College, London and Professor John Fuller of University College London to
evaluate the incidence and risk factors for diabetes-related amputation in
Barbadians. My local collaborators were Professor Henry Fraser and Dr. Ramesh
Jonnalagadda, and we were ably assisted by Nurses Pissamai Maul and Patricia
Basdeo who collected the data, Ms. Simone Lorde (Podiatrist), Mr. Ian Sealy
(Cardiac Technician) and Mrs. Heather Hennis (Computing and Database
Management).
The study consisted of two principal elements: a study of
the incidence of diabetes-related amputations (i.e. new cases occurring during
the period of observation) and a case-control study of risk factors. A
case-control study consists of two groups: the cases are individuals who have
the disease/outcome (in this case persons with diabetes who had an amputation)
and controls are comparable individuals who are similar in every respect except
that they did not have the disease/outcome (i.e. persons with diabetes who did
not have an amputation). To identify controls, we mailed around 2000 persons
randomly selected from the population and asked them all to respond by stamped
addressed letter completing a brief questionnaire to ascertain whether they
suffered from diabetes. Since the pattern of response might negatively affect
the findings of the study, we went to heroic efforts to ensure that we accounted
for each individual mailed and this involved our research nurses visiting the
homes of persons who did not mail in their responses. The overall response rate
for those invited to participate was over 80%; a very credible outcome. The idea
underpinning a case-control study is to compare the frequency of possible risk
factors for amputation such as gender, lifestyle factors (including smoking
habits, alcohol consumption, activity), medical history (including duration and
control of diabetes and hypertension, complications such as heart disease or
stroke, medications etc..), markers of obesity and diabetic complications (such
as neuropathy and peripheral artery disease) between the groups. Should specific
risk factors be more frequent in the group with diabetes who had amputations,
the inference would be that such factors might have led to (or be causally
associated with) the risk of amputation. One factor which we considered to be of
particular interest was the use of footwear. We therefore evaluated the types of
footwear commonly worn (with the aid of pictures) and the usual patterns of
duration of use and locations worn. While it may appear to be self-evident that
the type of shoes worn by persons with diabetes might influence the risk of
amputation, no study had previously attempted to quantify this risk.
Our findings in the incidence study were that there were 110
amputations per year among persons with diabetes for every 100,000 persons in
the general population. This figure increases to 525 amputations per year for
every 100,000 persons with diabetes. We also compared Barbadians and
Caribbean-origin British residents aged 50 to 64 years with diabetes and the
amputation rates were 2.64 times higher in Barbadians. We conducted further
analyses comparing our findings with data from the Global Lower Extremity
Amputation Study which involved centers in America, the United Kingdom, Western
Europe and the Far East. While Barbadian men had modest rates of lower limb
amputation, Barbadian women with diabetes had inordinately high rates of both
minor (through the mid-foot or toes) and major amputation (through the leg or
thigh) which were exceeded only by Navajo Indian women in Montana!
With respect to the case-control study, we found that poor
blood glucose control (measured by an elevated glycosylated hemoglobin or GHb)
was linked to an increased risk of amputation (by approximately 40%). Poor
circulation in the lower limbs or peripheral artery disease also increased the
risk of amputation as did peripheral neuropathy (diabetes-related nerve damage).
These findings confirmed information published in other reports.
We found that footwear habits were significantly related to
risk of amputation. Our analyses revealed that going barefoot into the garden
almost doubled the risk of amputation, wearing rubber thong sandals or slippers
also doubled the risk of amputation, and wearing tight formal shoes (i.e.
wearing pointed toe leather shoes by men and high heeled pointed toe shoes by
women) increased the risk of amputation almost three and a half fold. Wearing
sneakers to work or town unexpectedly increased amputation risk some two-fold in
women. We suspect that this might be due to poor quality footwear (such as
canvas sneakers) not being hygienically maintained. In support of this view is
the observation that women who wore sneakers to work are almost invariably
labourers and their occupation has particular implications for the state of
their footwear. The news however, was not all distressing as we found that daily
foot self-examination reduced the likelihood of amputation 80%!
Many factors are relevant in the pathways that lead to lower
limb amputation. Factors are relevant both to persons with diabetes as well as
health care providers. Self care by the individual with diabetes is germane to
optimal blood glucose control through careful self-monitoring working closely
with care providers. We have now provided evidence about the importance of
footwear as a risk factor for amputation and the message is that persons with
diabetes must desist from going outside barefooted, wearing rubber thong
slippers, tight fashion shoes and poor quality sneakers. Education, strict
attention to best practice and development of the multidisciplinary approach to
diabetes care are routes to improving provision of care by the health
professionals. Several potentially preventable factors including foot care and
footwear habits were identified by this research and the challenge will be to
translate these findings to improvements in general diabetic care, patient
education and practices, as lower extremity amputations are eminently
preventable.
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