Diabetes in the elderly will be the epidemic in this Century. Current data suggests that about 20% of patients over the age of 65 will develop diabetes at some point in their life. At least half the patients are unaware that they have the disease yet these patients are still susceptible to the complications of the illness. Recently, the diagnostic criteria for diabetes have been changed which means that we are going to detect even more cases of diabetes in older individuals. It is now recommended that every person over age 45 should have a fasting blood sugar test once every three years to screen for diabetes. A fasting blood sugar test should be performed yearly in people who are at high risk which includes patients with hypertension, obesity, high cholesterol, a history of gestational diabetes, or a strong family history of diabetes.
One of the reasons that diabetes is underdiagnosed in older people is that the classic symptoms of diabetes do not often present themselves in the elderly. In general, older patients with diabetes are asymptomatic. If they have symptoms, they tend to be non specific such as fatigue, weakness, impaired concentration, etc. A blood sugar test should be part of the investigation of any older person who has non specific symptoms.
Diabetes is clearly a genetic disease but it is also clear that lifestyle factors make it more or less likely that an older person with a genetic predisposition will develop diabetes. For example, it has been shown that if you have a family history of diabetes you are much less likely to develop the illness as you age if you exercise regularly, keep your body weight as close to normal as possible and eat a diet which is high in complex carbohydrates and low in simple sugars and saturated fats.
In our laboratory we have done a number of studies in the last few years to define the metabolic abnormalities which occur in older people. We have discovered that diabetes in older people is very different from diabetes in middle aged subjects. The principle problem in obese older people with diabetes is that their tissues are resistant to the effects of insulin. The main difficulty for lean older people with diabetes is that their pancreas doesn’t secrete enough insulin. In designing a treatment plan for older people with diabetes their body habitus should be kept in mind.
The first thing to do when treating an older person with diabetes is to stop, if possible, any medications that might be contributing to increased blood glucose levels. The next thing to do is to look at risk factors. It is increasingly recognized that controlling risk factors is just as important as controlling blood sugar in older people. There is good evidence to indicate that older people with diabetes derive great benefit from rigorous control of hypertension and treatment of high cholesterol. In addition, the Hope Study has recently suggested that ACE inhibitors (a type of blood pressure pill) are useful for older people with diabetes who have other cardiovascular risk factors.
Many people ask why you would bother to treat diabetes aggressively in an older person. The rationale can best be provided by this example. The average 75-year-old woman in Canada has a life expectancy of 13 years. She can expect to spend at least half that time with a major disability. The principle cause of disability in this age group is cardiovascular disease. Older people with diabetes are more susceptible to cardiovascular diseases such as heart attack and stroke than older people without diabetes. Thus, anything that can be done to reduce the risk of cardiovascular events in older people with diabetes should reduce their risk of disability and increase their quality of life. Recent evidence suggests that older people with diabetes who have good control of their blood sugars and good control of other risk factors for cardiovascular disease like hypertension, are much less likely to suffer heart attack and stroke. Thus, there appears to be good evidence that treatment of diabetes and its associated risk factors will improve the quality of life in older people.
After risk factor modification has been attempted, the next thing to do with an older person with diabetes is to institute lifestyle modifications. It is abundantly clear that older people are able to adapt to lifestyle changes as well as younger people, and they may derive even greater benefit from modifications of diet and activity than younger patients. When lifestyle modifications fail, the next thing to do is to institute drug therapy. In lean older people with diabetes the first approach should be to use drugs to stimulate the production of insulin by the pancreas or give insulin to replace the insulin deficit. Unfortunately the risk of hypoglycemia (low blood sugar) associated with use of Diabeta (glyburide), the drug most commonly used to stimulate insulin secretion, increases exponentially with age. Gliclazide (Diamicron) is safer and is associated with a lower risk of hypoglycemia than Diabeta. Gluconorm is a new short-acting drug that also stimulates insulin release. There is no good data as yet on the frequency of hypoglycemia with this drug in older people. In terms of insulin preparations, there is some evidence to suggest that animal insulins such as pork insulin are associated with a lower frequency of hypoglycemia in older people with diabetes. Animal insulin should be considered for use in people who are being treated with human insulin and are not aware that their blood sugar has become low.
In obese older people with diabetes the principle problem is resistance to the effects of insulin. The drug of first choice is metformin which assists with weight loss and increases the sensitivity of the cells to insulin. Provided this is given carefully to older people, it is well tolerated if they have no significant liver, heart or kidney disease.
There are a number of drugs which can be used in older patients with diabetes who are either lean or obese. Acarbose (Prandase) decreases sugar absorption from the gastrointesinal tract and is reasonably well tolerated and effective in the elderly. Rosaglitazone (Avandia) has just been released for use in Canada. Experience with this drug in the elderly is limited. Avandia increases insulin sensitivity and may be of particular value in obese older people with diabetes. Finally, many new drugs are currently under investigation. For example, we are conducting a trial of GLP (glucagon-like peptide) in elderly patients with diabetes. This drug may prove to be an excellent medication for older people with diabetes since it assists with weight loss, increases insulin secretion from the pancreas, enhances insulin sensitivity and never causes hypoglycemia. The advent of this and other therapies means that the future is more positive for the elderly person with diabetes.
Dr. Grady Meneilly is active in research and education while specializing in geriatric diabetes.