Diabetics
Who Control Blood Sugar Today Are More Likely To Have Healthy Feet
And Nerves Tomorrow
People with diabetes who keep their blood sugar in check today will
probably have a far lower chance of developing foot pain or other
nerve damage tomorrow, according to new research results from a
national study.
In fact, the study shows that the positive effects of tight blood
glucose control can be seen more than a decade later. At the end of
the study period, patients who had controlled their blood sugar
tightly ever since the start of the study were 51 percent less
likely to have nerve problems than patients who started the study
at the same time but did not have the initial 5 year period of
intensive blood sugar control.
The study, published in the February issue of the journal Diabetes
Care, involved 1,441 people with Type 1 diabetes, also known as
juvenile diabetes. Although patients with the more common Type 2
form of diabetes were not involved, the results may have
implications for the 18 million Americans with Type 2
diabetes.
Two-thirds of all people with diabetes have some degree of nerve
problems, or neuropathy, related to their diabetes. The most common
sign is numbness or pain in the feet and legs, which can progress
over time to cause disability. Neuropathy plays a major role in
80,000 foot and leg amputations in American diabetics each
year.
"This is an exciting finding that adds credence to the idea of
metabolic memory, or the concept that there can be a durable effect
from early and sustained efforts to keep blood sugar low," says
senior author Eva Feldman, M.D., Ph.D., the DeJong Professor of
Neurology at the University of Michigan Medical School and director
of the U-M Neuropathy Center. "It suggests that good glucose
control clearly protects patients over the long term."
The new study marks the first time that tight blood sugar control
has been shown to have a long-term effect on the chance that a
person with diabetes will develop neuropathy. Similar findings have
been made for two other frequent complications of diabetes,
retinopathy (eye disease) and nephropathy (kidney disease).
The new findings come from the Epidemiology of Diabetes
Intervention and Complications (EDIC) study that grew out of the
national Diabetes Control and Complications Trial (DCCT). Funded by
the National Institute of Diabetes and Digestive & Kidney
Diseases, the DCCT began in the 1980s by randomly assigning people
with Type 1 diabetes to either tight blood-sugar control using
three insulin injections per day or an insulin pump, or to more
typical blood sugar control for the time, using one to two insulin
injections a day. The latter group was later encouraged to adopt
tight blood sugar control, and the EDIC study tracked all patients'
health.
The new paper reports results from eight years of neuropathy
assessments under the EDIC study, among 1,441 DCCT participants who
had no symptoms or signs of neuropathy at the end of the
DCCT.
The symptoms and signs were assessed using a standardized
questionnaire developed and validated by U-M researchers from the
Michigan Diabetes Research and Training Center. Called the Michigan
Neuropathy Screening Instrument, the questionnaire is completed by
both patients -- who report symptoms such as tingling, pain,
numbness, and sensitivity -- and by physicians, who complete a
physical examination of the patients' feet, including sensitivity
to touch and vibration, and the presence of calluses and sores that
the patients might not be able to feel because of nerve
damage.
Such foot problems can become infected and lead to open wounds that
can be hard to heal because of other aspects of diabetes. Unhealed
infections, if bad enough, can lead to decisions to amputate toes,
feet and legs. This "domino effect" starting with neuropathy and
leading to infection and amputation is the reason that current
guidelines call for people with diabetes to have annual foot
exams.
Feldman, who led the analysis along with research nurse Catherine
Martin, M.S., notes that the study looked at the percentage of
participants who had any positive sign of neuropathy on their
questionnaire or their foot examination each year of the EDIC
study, and then separated them according to which DCCT group (tight
glucose control or regular control) they had been in.
This allowed them to track the impact of prior tight glucose
control, even though all the participants were encouraged to
control their blood sugar tightly once they entered the EDIC phase
of the project. Test results taken each year show that the two
groups achieved very similar blood-sugar control in the later years
of the EDIC study, with levels of a measure called A1C around 8
percent for both groups.
After the first year, 28 percent of the regular-control patients
showed signs of neuropathy on their physical exam, though only 4.7
percent reported symptoms on their questionnaires. By contrast,
17.8 percent of the tight-control patients had neuropathy signs on
their foot exams, and 1.8 percent reported symptoms. The difference
between the two groups was highly statistically significant.
Over time, the difference between the two groups continued to be
significant, although the percentage of both groups that showed
signs or reported symptoms of neuropathy increased over time. By
the end of the eighth year of follow-up, almost 7 percent of the
participants who had been in the regular-control group reported
feeling symptoms of neuropathy, compared with about 3.5 percent of
the tight-control patients. And at the end of eight years, more
than 26 percent of regular-control participants had signs of
neuropathy on their physical exam, compared with just over 20
percent of tight-control participants.
The researchers calculated statistical likelihoods for these
measures. In all, participants who had begun with tight blood-sugar
control and stuck with it were 51 percent less likely to report
symptoms of neuropathy, and 43 percent less likely to show signs of
it, than those who had started out with regular blood-sugar control
and then gone to tight control. There were also differences between
the two groups in the incidence of open sores requiring medical or
surgical treatment, and in incidence of amputation.
In all, says Feldman, the results reinforce a key message for all
of today's diabetes patients, though Type 2 diabetics tend to have
other health problems that can interfere with the protective
effects of tight sugar control. That message: Check your blood
sugar levels regularly, and take steps to keep them under tight
control, with few extremes of low or high sugar.
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Meanwhile, Feldman and others are searching for the reason why
nerve cells are damaged by high blood sugar, and why it might be
more beneficial to start tight glucose control early. The EDIC
sites have received an NIDDK grant to make more precise
measurements of neuropathy signs among EDIC participants. And U-M
is offering five diabetic neuropathy clinical trials for different
types of patients.