Diabetes in the Elderly
George E. Shambaugh, III, M.D.
Scope of the problem
Diabetes is a major public health problem in the United States. The prevalence of type 2 diabetes, non insulin dependent diabetes (NIDDM), increases with age. With the progressive increase in numbers of aging individuals and the estimated three-fold increase in hospitalizations of diabetics compared to non diabetics (1), the economic burden is considerable. This burden is not likely to be alleviated in the foreseeable future as the diabetic population is being continuously augmented by heightened survival of offspring of diabetic pregnant women, and better management of diabetes during their adulthood. Management of blood sugars can slow the progress of complications, and the lowest glycohemoglobin has been shown to correlate with the slowest progression of complications (2,3). For the elderly, this means that careful management with a goal to minimizing glycohemoglobin levels may help to diminish morbidity and hospitalizations consequent to complications. The advantages and disadvantages of good glycemic control in the elderly have been listed by Fonseca and Wall (4). Hyperglycemia can cause osmotic diuresis with dehydration leading to a loss of vascular volume and tissue perfusion, renal damage with diminished clearances resulting several serious sequellae ranging from drug toxicity to a hyperosmolar state and increased blood viscosity leading to potential myocardial infarction and/or stroke. In addition, hyperglycemia impairs phagocytosis and mobilization of leukocytes to the sites of infection, as well as impairing wound healing. Thus hyperglycemia needs to be controlled. By contrast, rigid control of glucose levels results in hypoglycemia and altered functions of the CNS. This happens because the setpoint for autonomic response to hypoglycemia is lowered in a tightly controlled patient. Thus, tachycardia and sweating may be manifested only when the glucose levels fall below 40 mg/dl or may not occur at all. Unfortunately, the rest of the brain has no such setpoint. Oxygen utilization by the brain depends on glucose availability, and when circulating glucose levels are low, the brain suffers from hypoxia. This is manifested by impaired judgment and generalized seizures or localized transient ischemic episodes, and may occur without the anticipated sweating and tachycardia comprising the autonomic response to hypoglycemia. On the other hand, elevated ambient glucose levels may raise the setpoint for an autonomic response, and rapid glucose lowering can result in autonomic symptoms of hypoglycemia even though circulating levels of glucose are still within the normal range.
Management of the elderly diabetic
The cornerstone to management
is patient education. Instruction must be given regarding monitoring
of capillary glucose levels, appropriate diets, exercise, care
of the feet, care of the teeth and gums, and administration of
insulin including drawing up measured amounts of insulin, and
injection techniques. Instruction must also be given regarding
pathophysiology including the insulin sparing effects of exercise,
sexual dysfunction, and problems in vision. In this regard, the
available services from the nurse educator, podiatrist, sexual
dysfunction clinic, ophthalmology clinic, and nutrition services
must be introduced and emphasized. The misconceptions that too
much sugar in the diet makes diabetes worse, that ethnic diets
cannot be adjusted to include the patients specific dietary requirements,
and that impotence has to be accepted must be dispelled and specific
problems dealt with on an individual basis with the patient and
their partner.
Monitoring glucose levels
Many elderly diabetics cannot read gradations on an insulin syringe
and cannot estimate either the required quantity of insulin or
interpret subtle changes in color on a test strip. The newer meters
offer digital readout and a memory. The field of monitoring is
changing rapidly, and the certified diabetes educator is an invaluable
team player for providing current methodology to optimize monitoring.
If the patient is unable to monitor his or her sugars, a spouse
or caregiver should be enrolled in the patient teaching program.
The frequency of monitoring varies with the patient but we have
had the best compliance with monitoring capillary glucose levels
twice a day (before breakfast and before dinner) twice weekly
on non-consecutive days. Patients are additionally instructed
to check their glucose levels if they feel unusual, develop symptoms
of hypoglycemia, suffer from unexplained seizures, or polyuria.
Hemoglobin AlC is a useful measure of integrated changes in glucose
levels and is independent of fluctuations with diet, but is relatively
insensitive. Because hemoglobin remains glycosylated until it
is destroyed, changes in the percent glycosylated hemoglobin levels
occur slowly, and measurements more frequently than every three
months are not useful. Monitoring hemoglobin AlC will provide
an estimate of the effectiveness of any given therapeutic regimen
and complements but does not replace the capillary glucose measurements.
Diet
Nutrition is often a problem consequent to defective dentition,
loss of taste and an unwillingness to adapt to a change in a lifetime
of eating patterns, especially if specific ethnic foods are favored.
Fortunately, the composition of the diet [protein 10-20%, carbohydrate
55-60%, and fats 30% or less, equally divided between saturated
(10%), monounsaturated (10%), and polyunsaturated (10%) fats]
can be adapted to nearly every food selection, and the nutritionist
is trained to construct different ethnic diets containing the
composition of proteins, carbohydrates, and fats outlined above.
Thus, the patient needs to communicate specific food preferences
that would maximize dietary compliance. The important relationship
between fat ingestion and hyperglycemia needs to be explained
to the patient and subtle sources of fat such as chocolate need
to be stressed. In addition the patient must understand that cholesterol
is only present in products of animal origin, but that cholesterol-free
products containing saturated fats will increase their serum cholesterol
levels.
Exercise
Exercise is vital to
maintain muscle conditioning in the elderly and must be consistent
to optimize diabetes control. The easiest exercise is a daily
walk for 30 minutes, but in patients with severe arthritis, swimming
can provide an important substitute. We usually request assistance
from physical medicine and rehabilitation for those patients with
specific problems in conditioning to provide a stepwise program.
With aging, both the diabetic and non-diabetic develop some relaxation
of their longitudinal ligaments resulting in poor arch support.
The metatarsal heads are exposed to the brunt of weight bearing
with callous formation and difficulty in walking. In the diabetic,
ligament relaxation may accompany neuropathy, and repeated trauma
to the skin overlying the metatarsal heads can result in ulceration
and infection. All diabetic patients should be evaluated by a
podiatrist and utilization of orthotics considered.
Oral hypoglycemic agents
The oral sulfonylurea
agents work by stimulating insulin output by the pancreas. Thus,
a pancreas lacking islet cells (type 1 diabetes, chronic pancreatitis)
is incapable of responding to oral hypoglycemic agents. The two
agents, glyburide and glipizide, have a duration of action similar
to NPH insulin. Glipizide is metabolized by the liver and would
be preferred to glyburide if there is a problem with renal failure,
oral sulfonylurea agents should be given twice daily (before breakfast
and before or after the evening meal or at bedtime). If the patient
exercises, I usually begin treatment with the bedtime dose alone.
When the patient does not exercise, I begin with twice daily dosing.
While the maximum dose of glipizide is reported to be 20-40 mg
and glyburide 20 mg, the maximum response usually is seen at lower
dosages. If the patient does not respond to maximal doses with
blood sugars below 150 mg/dl, it is worthwhile to add metformin
to the regimen if renal function is adequate (creatinine clearance
greater than 60 cc/min). Metformin should be started at 500 mg
once a day at bedtime and can be increased after 2 weeks to twice
daily. This minimizes dose-related diarrhea and abdominal discomfort.
Metformin acts in several ways including inhibition of glucose
output by the liver. The rationale for a bedtime dosing is to
aim for a fasting glucose level of 120 or less and to have the
maximal hypoglycemic effect manifest itself during the day when
help is readily available rather than in the wee hours of the
morning.
Unlike the oral sulfonylureas or metformin, acarbose is an alpha
glucosidase inhibitor which is metabolized solely within the gastrointestinal
tract. Acarbose delays postprandial absorption of glucose, and
carbohydrates are absorbed in the lower small bowel. This results
in attenuation of the postprandial rise in glucose. The metabolic
actions of acarbose result in its principal side effects, flatulence,
abdominal cramping, diarrhea, and increased hepatic transaminase
levels. Flatulence and diarrhea diminish with time. The effectiveness
of acarbose is less than the sulfonylureas and metformin, but
can be used as an adjunct to therapy with the other agents. This
drug is contraindicated in patients with inflammatory bowel disease
or in patients predisposed to intestinal obstruction.
Troglitazone enhances insulin sensitivity in liver muscle and
adipose tissue. Unlike the sulfonylureas troglitazone does not
enhance insulin secretion. At an oral dose of 200 mg given twice
a day, troglitazone has lowered fasting blood glucose and glycosylated
hemoglobin in patients with type 2 diabetes. Severe idiosyncratic
hepatocellular injury with death or necessitating a liver transplant
has been reported with troglitazone. Patients should be checked
at the onset of therapy and monthly thereafter for 6 months, then
every 2 months for the remainder of the first year, and periodically
thereafter. Patients should be instructed to report immediately
any symptoms of hepatic dysfunction such as anorexia, nausea,
fatigue, abdominal pain, or dark urine, and the drug discontinued.
The drug should also be withdrawn if the ALT (SGPT) is >3 times
the upper limit of normal.
Insulin
Insulin output by the pancreas may be blunted by hyperglycemia,
a pathophysiologic state known as glucose toxicity. Thus a patient
with blood sugars consistently greater than 200 mg/dl who has
not responded to oral agents may return to a responsive state
following relief of the hyperglycemia with insulin. Prior to beginning
insulin, the patient must be reinstructed on monitoring of capillary
glucose concentrations, in addition to refamiliarization with
the symptoms of hypoglycemia. Because insulin is metabolized in
part by the kidneys the dose of insulin should be diminished in
patients with severe renal insufficiency. We usually begin patients
on 15-20 units of NPH before bed, and the patient instructed on
monitoring capillary glucose levels before breakfast, before lunch,
before dinner, and before bed. Injection sites are best limited
to the abdomen and the sites rotated. After at least four days,
the insulin dose should be reviewed and considerations of adding
a morning dose of insulin, whether to add supplements of regular
insulin or whether to begin a 70/30 regimen of NPH/regular can
be addressed. In type 2 diabetes, the glucose levels tend to fluctuate
much less erratically than in type l, and patients can be maintained
long term on twice daily capillary glucose levels (before breakfast
and before dinner). If patient's fasting sugars are consistently
elevated, a bed time insulin dose beginning with 15-20 units NPH
should be given with a goal to obtaining fasting glucose levels
of l00 to 120 mg/dl. The patient should always be encouraged to
exercise regularly. Recent reports indicate that metformin and
insulin are particularly effective in the management of type 2
diabetes, with minimizing hypoglycemia and weight gain (5). Once
this has been accomplished, the afternoon glucose levels can be
addressed with a regular exercise program such as walking 30 minutes
a day, the utilization of metformin and oral agents, or morning
insulin dosing, in that order. Hypoglycemia is tolerated poorly
in the elderly and should be avoided.
The goal of treatment of diabetes in the elderly is to avoid hypoglycemia
while aiming for a glycohemoglobin level of <8%. A sliding
scale for regular insulin may be used by patients who understand
that the only way to use a sliding scale is to do so in a prospective
manner. For example, glucose levels before lunch or dinner or
bed are usually obtained three hours after eating. The addition
of regular insulin should be governed by the previous preprandial
insulin dose and not by the glucose level per se. When the physician
instructs the patient on the prospective use of a sliding scale,
it must be remembered that responsibility for judging requirements
for insulin administration and the appropriate dose now belongs
to the patient. In my experience, many of the elderly patients
have difficulty in following a sliding scale and in many cases
it is easier to utilize a fixed dose of insulin and to have the
patient record glucose levels on a sheet of paper or in a book.
Levels are then reviewed with the patient and insulin adjustments
made at the time of the office visit. For a selected group of
patients who are difficult to control, lispro insulin is now available
with a rapid onset, i.e., 15-30 minutes following sc injection
and a peak of 3-4.5 hr. Because of this rapid response, this insulin
preparation can be given after meals and the dose tailored to
what was consumed. Many elderly patients may not, however, be
able to manage the calorie calculations that are required. In
general, the regimens of tight glucose control constructed for
a younger individual is not appropriate for the elderly.
Monitoring for control
Record capillary glucose levels twice daily, twice a week. Record hypoglycemic reactions and hyperglycemia and circumstances surrounding each event. Obtain hemoglobin AlC every three months.
Monitoring for complications
Microvascular Complications
These include retinopathy, nephropathy,
and neuropathy. Development and/or progression of
these complications is slowed by keeping the HgbAlC below 8.0.
Generally, the lower the HgbAIC the slower the development of
microvascular complications. Macrovascular complications including
peripheral vascular disease are benefited by good control, but
the relation to HgbAlC is not as well defined. Control of hyperlipidemia
and hypertension is important. Cessation of smoking is essential.
Retinopathy
Diabetic patients should have an annual ophthalmology appointment
to examine the retina and the retina should also be examined routinely
for retinopathy at each quarterly office visit.
Nephropathy
A urine dipstick for protein at the quarterly office visit and
if negative (protein <300mg), a urinary microalbumin/creatinine
ratio should be performed. If this is abnormal, the patient should
be placed on ACE inhibitors. A urinary microalbumin/creatinine
ratio should be done annually.
Neuropathy
Check deep tendon reflexes, sensation in feet with a plastic filament
(6.10). Failure to feel this in a non-calloused area is a sign
that protective sensation is absent. Most patients without neuropathy
can feel a thinner plastic filament (5.07). Proprioception and
timed vibration sense which can be done with a C128 tuning fork
should be performed every six months (normal time for feeling
vibration at the med malleolus is 16-20 seconds). Ongoing history
regarding incontinence and/or impotence is important. In this
regard, pharmacologic causes of neurogenic impotence are very
common, but vascular problems may also contribute. For example,
diuretics needed to control blood pressure may cause impotence
by lowering penile arterial pressure. Inspection of the feet by
a physician should be done quarterly, and an evaluation by a podiatrist
every six months.
1. Center for Economic Studies in Medicine: Direct and Indirect Costs of Diabetes in the United States in 1987. Alexandria, VA, American Diabetes Association, 1989.
2. 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 329:977-986, 1993.[Citation]
3. Intensive blood-glucose control
with sulphonylureas or insulin compared with
conventional treatment and risk of complications in patients with
type 2 diabetes
(UKRDS 33). Lancet 352:837-853,1998.[Citation]
4. Fonesca V. and J. Wall. Diet and Diabetes in The Elderly. Clin in Geriatr Med 11:613- 624, 1995.
5. Yki-Jarvinen H, et al. Comparison of bedtime insulin regimens in patients with type 2 diabetes mellitus. Ann Int Med 130:389-396,1999.[Citation]
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