Diabetes in the Elderly

Monitoring

Patients should be monitored with regular laboratory evaluations, including fasting blood (or plasma) glucose determinations, to assess therapeutic response and obtain the minimum effective dosage of antidiabetic medications. Whenever possible, self-monitoring of blood glucose by the patients should be encouraged. Urine glucose concentrations correlate poorly with blood glucose, and should be avoided. Following initiation of treatment and subsequent dosage titration, control can be determined by evaluating glycosylated hemoglobin (HbA1c) levels at intervals of approximately 3 months.

Management

As with any older patient, a holistic approach is needed in the context of the overall health, lifestyle, environment, and wishes. For younger patients, many consider aggressive care with the goal of achieving euglycemia as the standard therapy. But in the older diabetic, there are two levels of care - basic and aggressive. Basic care is indicated for those individuals in whom the primary goal of treatment is the prevention of symptomatic hyperglycemia. The average glucose levels to achieve this goal are approximately 11.1 mmol/L of postprandial sugar or the level at which glycosuria is minimal. The elimination of glycosuria is important, as this predisposes the diabetic to volume depletion, hypotension and poor tissue perfusion. Glycosuria also causes weight loss due to loss of calories in the urine, catabolic state, loss of lean body tissue and may predispose to infections and other complications of malnutrition.

Aggressive care is appropriate when the goals of treatment include the prevention of long-term complications. Euglycemia with a fasting glucose level less than 6.1 mmol/L is optimal, with normal levels of glycosylated hemoglobin. There are several benefits of euglycemia, both immediate and long term. (Table1)

The decision regarding the treatment goals is the most important in the management of DM in the elderly. The patient and the treating physician should make this decision jointly. Current medical problems and the estimated life expectancy have to be kept in mind while deciding on the type care to be given. Until further studies are available that can help us in deciding the type of care to be given to the elderly, many elderly patients deserve the same consideration as younger adults regarding aggressive management of their disease. Age per se should not be considered as an indication for providing only basic care to any elderly diabetic.

Table 1: Benefits of euglycemia

Immediate

Less nocturia, polyuria and hypovolemia.
Better leukocyte function and chemotaxis, hence, fewer infections
Better wound healing

Long term

Slower progression of retinopathy, cataracts, neuropathy and nephropathy
Reduced lipoprotein A and glycosylated hemoglobin, with resultant reduction in cardiovascular mortality.

Regardless of the treatment goals decided, all older diabetics should receive care that meets minimum standards as shown in Table 2
The four standard modalities of diabetes treatment - diet, exercise, oral hypoglycemic agents, and insulin - all merit consideration in older diabetics also.
Pharmacological therapy of an elderly diabetic poses many problems. Drugs may be used inappropriately, when the effects of treatment may be worse than the symptoms for which it was given. Polypharmacy is a common problem, often due to the presence of multiple co-existing diseases, but sometimes drugs are prescribed by several doctors who are not individually aware of the patient's other medications, leading a host of drug interactions. Drug compliance is also poor in the elderly due to deficient memory, sight or hearing, or due to unacceptable adverse effects. Pharmacodynamics of many drugs are altered in the elderly due to many physiologic changes, increasing the propensity for drug toxicity.

Table 2: Minimum Standards of Care for Older Adults with Diabetes Mellitus

Initial Evaluation
Complete history and physical examination
Geriatric assessment (functional assessment)
Laboratory examination: fasting blood glucose, glycosylated hemoglobin, fasting lipid profile, creatinine, urinalysis, and ECG.
Ophthalmological evaluation
Dietary assessment

Continuing Care
Use of treatment as needed to meet target glucose levels
Assessment of blood glucose levels as frequently as needed to make sure that goals are being met
Annual assessment for diabetic complications
Annual review of geriatric (functional) assessment

Diet

Many elderly are managed with diet alone with various degrees of success. But, the elderly may find it more difficult to adhere to a strict dietary regimen than young adults. Moreover, there are many special considerations in the elderly like financial difficulties, mobility problems, poor food preparation skills, long-standing dietary habits, difficulty in following dietary instructions, decreased sense of taste and increased frequency of constipation, which hinder their ability and motivation to follow the advised dietary protocol. It is important to tailor the dietary advice to the individual patient. Unnecessarily strict dietary control in a very old person with a short life expectancy may reduce the quality of life without any significant therapeutic benefits.

No specific modifications in the diet is currently recommended by the ADA have been recommended for older diabetics. However, vitamin and mineral supplements are indicated when the caloric intake falls below 1000 kilocalories per day to prevent deficiency syndromes.

Exercise

The role of exercise as therapy in elderly diabetics is controversial. One study suggests that exercise, as a significant therapy for control of DM may not be feasible for older adults.

Table 3: Potential benefits and risks of exercise in elderly diabetics.

Benefits

Improved exercise tolerance
Improved glucose tolerance
Improved maximal O2 consumption
Increased muscle strength
Decreased blood pressure
Decreased body fat
Increased muscle mass
Improved lipid profile
Improved sense of well being

Risks

Sudden cardiac death
Foot and joint injuries
Hypoglycemia

There are many potential benefits along with certain risks (Table 3). Most of the benefits are related to the improvements in the risk factors for cardiovascular disease, which is a significant complication of diabetes in the elderly. Because of the prevalence of silent coronary artery disease in this population, older adults with diabetes should undergo an exercise tolerance test in consultation with their treating physicians before they begin any exercise programme. The level of exercise should be gradually increased and tailored to the exercise capacity of the patient. Patients must wear proper footwear during exercise, and care must be taken to avoid injury and falls that can be disastrous in the elderly. Hypoglycemia must be avoided by adequate snacks before starting the exercise.

Medications

Sulfonylureas

Approximately 70% of the prescriptions for these anti-diabetics are for individuals over the age of 60 years. The safety profile and easy dosage schedule make sulfonylureas the cornerstone of therapy in the treatment of type-2 DM in the elderly. Because type 1 DM is uncommon in older adults, most are eligible for a trial of oral agents when dietary management fails.

Hypoglycemia, however, is a major safety concern with sulfonylureas. Up to 20% of patients taking sulfonylureas experience symptoms of hypoglycemia over a six-month period. There are multiple factors associated with ageing that increase the risk of hypoglycemia, including the age related alteration of hepatic and renal functions that alter drug metabolism and excretion. Ageing is also associated with impairments in the autonomic nervous system and reductions in alpha- adrenergic receptor function suggesting decreased response to hypoglycemia in the elderly. This can be dangerous as they may not present with warning symptoms such as tremors, sweating or palpitation and may directly come with neuroglycopenic symptoms such as convulsions, focal neurological deficits or coma.

The elderly are frequent users of drugs that are known to increase the risk for hypoglycemia, including beta- blockers, salicylates, warfarin, sulfonamides, tricyclic anti-depressants and alcohol. Many elderly persons receive inadequate education regarding the signs and symptoms of hypoglycemia. Severe hypoglycemia may follow glibenclamide use in the elderly. Metabolism of this drug yields two active metabolites, and in the elderly, the clearance of these metabolites appears delayed. For this reason, glipizide and gliclazide, which have shorter half-lives and few or no active metabolites, are preferred sulfonylurea agents in the elderly diabetics.

One more concern with sulfonylurea therapy has been the ability of these agents to cause vasoconstriction of small vessels, including the coronary arteries. The latest generation sulfonylurea, glimepiride, appears to be more selective than the earlier agents. Besides exhibiting less hypoglycemia compared to glibenclamide, this drug appears to be more specific for islet cell potassium channels. Thus, in contrast to earlier sulfonylureas, glimepiride is less likely to produce coronary artery vasoconstriction. Sulfonylurea tablets should be taken half-hour before meals. The drug should be started at a low dose, about half of the standard, and gradually increased if required.

Biguanides

In overweight and obese diabetics, with normal renal functions and stable cardio-respiratory status, biguanides can be used if diet alone is not sufficient or as an add-on therapy with sulfonylureas. When used alone, they do not produce hypoglycemia. Metformin should not be used in conditions that are associated with increased generation of lactate or its decreased clearance, such as renal insufficiency, hepatic disease, alcoholism, severe congestive cardiac failure, severe peripheral vascular disease, and severe chronic obstructive pulmonary disease. Metformin should be administered immediately after meals to avoid gastrointestinal disturbances. Starting with a smaller dose can reduce this adverse effect.

Alpha- Glucosidase inhibitors

Acarbose is an alpha- glucosidase inhibitor and reduces post-prandial hyperglycemia with lesser effect on fasting glucose levels. The advantage of acarbose in the elderly is its safety profile. However, gastrointestinal disturbance is the major adverse effect of acarbose. Starting with a smaller dose and gradually increasing the dosage if required can minimize this.

Repaglinide

Repaglinide is a short-acting insulinotropic antidiabetic agent. Acting principally by augmenting endogenous insulin secretion from the pancreas in response to a meal, this controls the postprandial glucose excursions. This is a short- acting drug and can be taken with meals. The safety and efficacy of repaglinide appear to be similar in geriatric and younger patients.

Thiazolidinediones

There are currently three drugs in this group - troglitazone, rosiglitazone and pioglitazone - of which the former has been withdrawn due to fatal hepatotoxicity. At present, there is no evidence that the latter two drugs have a similar hepatotoxicity, but precaution should be taken in patients with liver dysfunction. These are used alone (monotherapy) or in combination with sulfonylureas, metformin, or insulin for the management of type 2 DM. They act principally by increasing insulin sensitivity in target tissues, as well as decreasing hepatic gluconeogenesis. These are insulin sensitizers that act without stimulating insulin release from pancreatic beta cells, thus avoiding the risk of hypoglycemia. Hence these may be well suited for use in the elderly. The clinical usage recommendations and pharmacokinetics of thiazolidinediones in the elderly are similar to those in the younger diabetics. However, cardiac function must be assessed in all patients before starting these drugs as they can precipitate cardiac failure in patients cardiac dysfunction. Liver enzymes should be monitored monthly for the first six months, every two months for the next 6 months, and every 3 to 6 months thereafter.

Insulin

Insulin is indicated when treatment goals are not being met with diet, exercise, and oral medications. No specific regimen or form of insulin has been identified as particularly advantageous to the elderly. It is difficult to achieve euglycemia with a single daily dose of intermediate acting insulin. Although always a stressful therapy to initiate, insulin injections for the elderly can be particularly complex, predisposing to medication error. Problems include visual impairment and difficulty in drawing and injecting the exact dose of insulin, impaired manual dexterity, decreased sensation in the hands, limited access to injection sites, and difficulties in monitoring blood glucose. However, none of these considerations are absolute contraindications to insulin therapy, solutions can usually be found for each.

Insulin Analogues

Insulin lispro is an analogue that has a more rapid onset and shorter duration of action compared with regular insulin. Therefore, it is associated with greater relative reductions in postprandial blood glucose concentrations and may provide greater patient convenience in terms of the timing of insulin injections in relation to meals with the added benefit of less incidences of hypoglycemia. This is a specific advantage in the elderly as patients can be advised to take insulin immediately before meals precluding the need to wait for half-hour after taking injection.
In conjunction with long-acting insulin, such as insulin glargine or ultralente insulin, the rapid-acting analogues provide tight control of blood glucose levels throughout the day. Insulin glargine has a nearly peakless profile and lasts for more than 24 hours. 38 For geriatric use the initial dosage, dose increments, and maintenance dosage should be conservative to avoid hypoglycemia.

CONCLUSION

As age advances, the quality of life becomes more important than the length of life. A well-controlled elderly diabetic who has no major complications, and is adept at self-care, should be the goal of all physicians treating diabetic patients..