Diabetes Mellitus
Diabetes mellitus is a disease in which blood sugar (glucose) levels are abnormally high because the body does not produce enough of the hormone insulin or fails to respond to insulin.
Diabetes is extremely common in older people, of whom about 15 to 25% have the disease. Diabetes can lead to such complications as chest pain (angina) and heart attacks, heart failure, stroke, kidney failure, blurred vision and blindness, pain and loss of sensation in the hands and feet, and amputation. Many of these complications arise because diabetes leads to narrowing and leakage of blood vessels, which impairs circulation and damages tissues. These complications are even more likely in people who smoke or have high blood pressure and high cholesterol levels, both of which often accompany diabetes. Fortunately, many complications can be prevented by quitting smoking and by taking steps to control blood pressure and cholesterol levels as well as blood sugar levels.
Causes
Diabetes is categorized as type 1 or type 2, each with a different cause. Type 2 diabetes is the main form of diabetes among older people. Obese older people with a family history of diabetes have the highest risk of developing type 2 diabetes. In type 2 diabetes, the body does not respond normally to the insulin produced. This phenomenon is called insulin resistance. Also, the body may not make enough insulin. Type 1 diabetes is much less common among older people. In type 1 diabetes, the body does not produce any insulin.
When sugar from food is absorbed into the bloodstream, the pancreas responds by producing insulin. Insulin plays a key role in moving sugar from the bloodstream into the cells, where it is then converted into energy. The body uses this energy to function; sugar is the fuel on which the body runs.
If the body cannot adequately produce or respond to insulin, sugar cannot enter the cells. Instead, sugar accumulates in the blood, and the cells must turn to other sources for energy.
For additional detail on this topic, see Risk Factors for Type 2 Diabetes.
Symptoms
People with type 2 diabetes may have no symptoms for months or even years before the disease is diagnosed. The first symptoms of diabetes, which may be subtle, result from the high level of sugar in the blood. When the blood sugar level rises too high, sugar spills into the urine. The kidneys then must excrete additional water to dilute the sugar. Therefore, a person with diabetes urinates large volumes (polyuria). The loss of water due to excessive urination also creates abnormal thirst (polydipsia). Also, because the body cannot use sugar as energy, a person with diabetes may experience excessive hunger and thus eat more (polyphagia) and yet still lose weight. Other symptoms include blurred vision, drowsiness, decreased endurance during exercise, and lightheadedness on standing, a sign of dehydration.
Occasionally, blood sugar levels in people with type 2 diabetes become extremely high. These extremely high levels often result from failing to take drugs to control blood sugar or from stress to the body, such as infection or surgery. When blood sugar levels rise extremely high, the person may become severely dehydrated, which may lead to confusion, drowsiness, seizures, and coma—a condition called nonketotic hyperosmolar (or hyperglycemic hyperosmolar) coma.
Symptoms may result from complications that develop gradually over years, sometimes even before diabetes is diagnosed. Chest pain or heart attack can result from poor blood flow to the heart. Sudden loss of strength, sensation, coordination, speech, or vision can result when poor circulation to the brain causes a stroke. Gradually worsening vision can also occur with damage to blood vessels in the eyes (retinopathy). Decreased urination and swelling in the legs and other parts of the body can occur when poor blood flow results in kidney failure. Pain or numbness and tingling in the hands and feet can occur when nerves are damaged by high blood sugar (diabetic neuropathy). Leg pain with walking (claudication) can be an indication of poor blood flow. Serious foot infections and ulcers can develop when not enough blood reaches the legs and feet. Sudden loss of function in a leg can occur if poor blood flow to a nerve damages the function of the nerve. Skin can be damaged by poor blood flow as well.
Diagnosis and Screening
Health care practitioners perform blood tests to diagnose diabetes. The tests are performed in people with symptoms of high blood sugar or complications of disease. The same tests are often used to screen for diabetes in people without symptoms: many older people have the disease but do not know it.
A simple blood test called a glucose test is most commonly used to make the diagnosis. The level of sugar (glucose) in the blood is measured, usually after the person has fasted for at least 8 hours. Sometimes the blood sugar level is measured randomly, without regard to when the person last ate, but this test is not as accurate. In a person who does not have diabetes, blood sugar levels after fasting range from about 70 to 100 milligrams per deciliter (mg/dL) of blood. The levels may be higher if the person has recently eaten. Diabetes is the likely diagnosis if the blood sugar level is 126 mg/dL or higher if the person fasted before the test or 200 mg/dL or higher if the test was performed at random. But a repeat test must be done if the first result is higher than 100 mg/dL (recently changed from 110 mg/dL at the recommendation of an expert panel). The diagnosis of diabetes mellitus is confirmed if any one of the following results is obtained:
- Two fasting levels are 126 mg/dL or higher
- Two random levels are 200 mg/dL or higher
- A fasting level is 126 mg/dL or higher and a random level is 200 mg/dL or higher.
People who have two or more fasting blood sugar levels between 100 and 125 mg/dL (a condition sometimes called impaired fasting glucose) should have this test repeated every year. People in whom both fasting blood sugar levels are less than 100 mg/dL should have the test repeated at least once every 3 years.
Once diabetes has been diagnosed, the person should be screened for disease complications at least once a year. The eyes should be examined by an eye specialist, who can detect and treat retinopathy before it leads to vision loss. Kidney problems can be detected with urine and blood tests. Blood cholesterol levels should be checked. An electrocardiogram is sometimes used to find evidence of heart damage, although the information that this test provides is limited. In some cases, an exercise (or other form of) stress test is done to find out if blood flow to the heart is poor.
A person's feet should be examined closely once or twice a year by a health care practitioner for poor blood flow, decreased sensation, skin breakdown, and infection. Self-examination of the feet daily or weekly is also important for early detection of skin breakdown. Breakdown, which can involve cuts, blisters, and sores, should receive medical attention.
Prevention
Diabetes often can be prevented, though usually not without some work. Losing weight through dietary changes, increased physical activity, or both is a very effective preventive measure. Brisk walking for 30 minutes a day is one type of beneficial physical activity. Preventive measures are especially important for people whose blood sugar levels are only slightly elevated. Some drugs used to treat diabetes may also be used preventively for people at high risk of developing the disease. However, drugs are no substitute for proper diet, exercise, and weight loss.
Treatment
The goal of treatment is to maintain blood sugar levels within the normal range so as to prevent or control symptoms and reduce the risk of developing complications. However, some people with other diseases, such as advanced cancer, may not benefit from strict control of blood sugar levels if one or more of their other diseases are life threatening. Strict control may also be impossible for people with dementia or poor eyesight.
The focus of diabetes treatment is not limited to control of blood sugar. Management of associated cardiovascular risk factors, such as high blood pressure and elevated cholesterol, are also important. Treatment involves education, diet, exercise, drugs (for most people), and frequent monitoring of blood sugar levels.
Education: Learning about diabetes, understanding how diet and exercise affect blood sugar levels, and knowing how to avoid complications are essential. A nurse trained in diabetes education can provide information. Diabetes education programs are available in many communities, the cost of which is now covered by many health insurance programs, including Medicare.
Diet: Maintaining a healthy diet is extremely important for people with diabetes. Well-balanced, healthy meals that include a variety of foods should be eaten at regular times. Starchy foods (such as bread, pasta, and rice) and sweets (such as fruits and foods with added sugar) are most likely to increase blood sugar levels. Foods with a high sugar content should be eaten sparingly. Because people with diabetes tend to have high blood cholesterol levels, foods containing saturated fats should be eaten sparingly as well.
Dietary measures alone are sometimes enough to maintain a healthy weight and control blood sugar levels. However, many older people have difficulty implementing such measures. In some cases, older people with diabetes who also have other diseases that can be affected by diet may become confused about how to follow recommendations for a healthy diet. Some people have difficulty because of long-held food preferences. In addition, they may not have control over what they eat because someone else is cooking for them or because they are living in a nursing home or institution. When people with diabetes do not do their own cooking, those who shop and prepare meals for them must also understand proper diet. Older people and their caregivers generally benefit from meeting with a dietitian to develop an optimal eating plan.
Exercise: People with diabetes should be physically active. Putting extra physical activity into ordinary activities, such as walking instead of driving to a store or taking stairs instead of elevators, can often help. However, formal exercise is often needed. Most people can find some form of exercise they enjoy, such as swimming, playing tennis, riding a stationary bicycle while watching television, walking in a mall, or participating in an exercise program offered by a local community center.
Drug therapy: Drug therapy is started when diet and exercise do not adequately lower blood sugar levels or when a person's living conditions, physical strength, or motivation make proper diet and exercise impossible.
Oral antihyperglycemic drugs are usually the first drugs given. There are many different types of oral antihyperglycemic drugs, including biguanides, sulfonylureas, meglitinides, thiazolidinediones, and glucosidase inhibitors. A doctor may prescribe one of these drugs alone or may combine two or more of them. Some of these drugs work by stimulating the pancreas to produce more insulin, others increase the body's response to the insulin it produces, and still others block the intestines from absorbing sugar.
Insulin is usually given if oral antihyperglycemic drugs alone cannot control blood sugar levels adequately. As many as half of the people with type 2 diabetes eventually require insulin treatment to control blood sugar levels. Temporary insulin treatment is also sometimes necessary during periods of stress, such as illness, surgery, or hospitalization.
Insulin is divided into four basic types based on how quickly it works and how long it lasts. Rapid-acting insulin (such as lispro or aspart) is the fastest and shortest acting. It is taken as several daily injections up to 5 minutes before meals or just after eating. Rapid-acting insulin reaches its maximum effect in 45 to 75 minutes and works for 2 to 4 hours. Short-acting insulin (such as regular insulin), which is taken 30 to 60 minutes before a meal, reaches its maximum effect in 2 to 4 hours and works for 6 to 8 hours. Intermediate-acting insulin (such as lente or NPH) starts to work in 2 to 3 hours, reaches its maximum effect in 6 to 10 hours, and works for 18 to 26 hours. It may be used in the morning to control blood sugar levels for the first part of the day or in the evening to control blood sugar levels during the night. Long-acting insulin (such as ultra-lente or glargine) begins to work very slowly but lasts for 24 to 36 hours. Long-acting insulin usually has its maximum effect at 14 to 24 hours. Glargine, unlike other forms of long-acting insulin that reach a maximum effect at a specific time, works continually at about the same level of effectiveness.
The four types of insulin can be taken in a variety of ways. Insulin treatment is tailored to individual needs, often starting with a single daily injection and progressing to a more complicated regimen. For many people, a single daily injection of an intermediate- or long-acting insulin, sometimes combined with oral drugs, may control blood sugar levels. However, for some people this regimen may not prevent high blood sugar levels after meals.
Better control can usually be achieved by combining two types of insulin—for example, a rapid-acting and an intermediate-acting insulin—in one or more daily doses. Administering a combination requires more skill, because doses may need to be varied depending on factors such as the size of the meal and the time of day. The best control is often achieved by injecting a rapid-acting insulin at mealtime and an intermediate- or long-acting insulin in the morning and evening.
The types of insulin taken and the frequency with which they are taken may change based on the person's diet, exercise, and blood sugar patterns. In addition, insulin needs may change if a person experiences weight changes, emotional stress, or illness, especially infection.
A doctor considers several factors when choosing insulin therapy, including the person's blood sugar levels, the constancy of those levels from day to day, and the person's ability and willingness to monitor his blood sugar levels and to adjust the insulin dosage.
Some older people may have difficulty injecting insulin because of impaired vision, which may make it hard to prepare an accurate dose in a syringe. Others may have problems manipulating the syringe as a result of arthritis, Parkinson's disease, or stroke. A caregiver can help by preparing the syringes ahead of time and storing them in the refrigerator. Also, magnifying devices may allow a person with limited vision to see the measurements on the syringe more easily. Prefilled insulin pen devices, either disposable or with replaceable cartridges, may be easier for people with physical disabilities to use. Some of these devices have been specially designed with large numbers and easy-to-turn dials.
Sometimes, complications from insulin treatment develop. Insulin injections can affect the skin and underlying tissues. An allergic reaction, which occurs rarely, produces pain and burning, followed by redness, itchiness, and swelling around the injection site for several hours. More commonly, the injections either cause fat deposits, making the skin look lumpy, or destroy fat, causing indentation of the skin. However, these problems are less common with newer insulins and can usually be prevented by rotating the injection site.
Monitoring blood sugar levels: Regardless of whether a person takes insulin or oral antihyperglycemic drugs, monitoring blood sugar levels is essential to the treatment of diabetes. Blood sugar levels can change from hour to hour in response to diet, physical activity, stress, illness, drugs, and site of insulin injection. Blood sugar levels rise in many people in the early morning because of the normal release of hormones (growth hormone and cortisol), a reaction called the dawn phenomenon. Blood sugar levels may also rise if the body releases sugar in response to low blood sugar levels (Somogyi effect).
Monitoring blood sugar levels provides the information needed to detect these changes and to make the necessary adjustments to diet, exercise, and drug regimens. Most people with diabetes should keep a record of their blood sugar levels and report them to their doctor. Many people can learn to adjust their insulin dose on their own as necessary. The number of times per day that blood sugar should be checked depends on many factors, including the type of insulin a person is taking and the way blood sugar levels change in response to meals. Some people check their blood sugar only once or twice a day, whereas others check it more than 4 times a day.
Most blood sugar monitoring devices, especially newer models, use only a tiny drop of blood. The blood sample is obtained by pricking the tip of the finger with a small lancet. Some models allow for testing at sites less painful than the fingertips, like the forearm. The lancet is a tiny needle that can be placed in a spring-loaded device that easily and relatively painlessly pierces the skin. A drop of blood is then placed on a test strip. The test strip undergoes a chemical change in response to sugar. A palm-sized machine reads the changes in the test strip and reports the result on a digital display.
Special devices are available for use by people with poor vision or other physical limitations, such as limited manual dexterity due to arthritis, tremor, or stroke. Some devices have large numerical displays that are easier to read. Special devices with audible instructions and results are available as well. A new device reads blood sugar levels through the skin: no blood sample is necessary. The device is worn like a wristwatch and measures the blood sugar level every 15 minutes. Alarms on the device can be set to sound when blood sugar levels drop too low or rise too high. However, results must be compared periodically to those of a blood test. Also, the device may irritate the skin, is somewhat large, and does not work when a person moves a lot or becomes sweaty. This device cannot completely replace the need for blood testing. Because there is a wide variety of meters available, a person with special needs may wish to consult with a diabetes educator to determine which meter is best for him.
Virtually all meters are sufficiently accurate when used properly. Most important is to make sure that test strips have not exceeded the expiration date, that an adequate blood sample is obtained, and that "control solutions" and check strips are used periodically to confirm that the meter is functioning well.
Although urine can also be tested for the presence of sugar, checking urine is not a good way to monitor treatment or to adjust therapy. Urine testing can be misleading, because the level of sugar in the urine may not reflect the level of sugar in the blood. Sugar levels in the blood can get very low or reasonably high without any change in the sugar levels in the urine. People with type 1 diabetes are sometimes asked to check their urine for the presence of ketones, which indicates a severe lack of insulin and a potential health emergency. But for people with type 2 diabetes, urine testing for sugar or ketones is rarely appropriate.
Health care practitioners can monitor blood sugar levels using a blood test called hemoglobin A1C. Most doctors recommend that this test be performed every 3 to 6 months. Unlike blood tests that reveal sugar levels at a particular moment, hemoglobin A1C measurements provide a measure of blood sugar levels over the previous 2 to 3 months. The normal level for hemoglobin A1C is 6% or less. People with diabetes may not be able to achieve normal levels, but good control of blood sugar should bring a person close. The goal in most cases is to achieve a hemoglobin A1C below 7%. Levels above 8% show poor control, and levels above 10% show very poor control.
Prevention and Treatment of Diabetes Complications
Many, if not all, diabetes complications can be prevented by keeping blood sugar levels as close to normal as possible at all times.
The eyes, kidneys, and feet should be examined annually by a doctor to detect complications before they cause permanent damage. Cholesterol levels and blood pressure should be checked every year too. Treatment of high blood pressure and cholesterol levels and attempts to stop smoking can prevent the buildup of plaque (atherosclerosis) in blood vessel walls. Specific treatments may also help prevent complications. Laser surgery can seal leaking blood vessels in the eye and prevent permanent damage to the retina. Progression of kidney complications can be slowed or stopped with angiotensin-converting enzyme (ACE) inhibitors or angiotensin II receptor blockers. Indeed, many experts believe that most people with diabetes should receive these drugs to prevent kidney damage from diabetes. Prevention of stroke and coronary artery disease involves daily aspirin, cholesterol-lowering drugs, ACE inhibitors, and other blood pressure–lowering drugs as needed. The treatment of nonketotic hyperosmolar coma involves fluid and electrolyte replacement and insulin injection.
Complications of Treatment
The most common complication of treating high blood sugar levels is low blood sugar levels. Having low blood sugar levels is serious, develops rapidly, and can be life threatening. Older people who are frail, who are sick enough to require frequent hospital admissions, or who are taking multiple drugs are at greatest risk. Of all available treatments for diabetes, sulfonylureas—especially glyburide and glipizide—and insulin injections can cause low blood sugar levels. Drugs such as metformin and the thiazolidinediones rarely, if ever, cause low blood sugar when used alone.
Common symptoms of low blood sugar include sweating, nausea, warmth, anxiety, shakiness, palpitations, hunger, headache, blurred or double vision, confusion, and difficulty speaking. Older people are at greater risk of low blood sugar levels when they use long-acting sulfonylurea drugs. They are also more likely to experience serious symptoms, such as fainting and falling, and to develop stroke as a result of low blood sugar. In the worst cases, low blood sugar can cause coma, permanent brain damage, and even death. For this reason, low blood sugar levels must be treated immediately.
Sugar must get into the body within minutes to relieve symptoms of low blood sugar and prevent harm to the brain. A person with diabetes can usually eat or drink some form of sugar. Fruit juice, milk (which contains lactose, a type of sugar), and regular soda (not diet) are usually effective. So is eating a piece of cake, fruit, or another sweet food. People with diabetes can also carry glucose tablets or gels, which are particularly convenient and easy to transport. Most of the time, 4 to 6 ounces of juice or 4 to 5 glucose tablets are sufficient to correct hypoglycemia. Care should be taken not to overtreat, because an abnormally high blood sugar level will result. When sugar is unavailable or the person is unconscious, emergency medical personnel may have to inject glucose into a vein.
Ideally, blood sugar is tested about 20 to 30 minutes after sugar has been eaten to ensure that the blood sugar level has increased to the normal range.
Another treatment for low blood sugar is glucagon. Glucagon can be injected into the muscle and causes the liver to release large amounts of glucose within minutes. Small transportable kits containing a syringe filled with glucagon are available for use in emergency situations. Glucagon is generally used only if a person is unable to take adequate amounts of sugar by mouth.
Outlook
The outlook is excellent for older people with diabetes who are willing and able to eat a proper diet, exercise, maintain a healthy weight, and take blood sugar–lowering drugs regularly. However, older people who choose not to or who are unable to adhere to recommended treatment measures are at risk of developing the serious complications of diabetes. Most complications of diabetes are progressive and tend to develop after only a few years of having the disease. Fortunately, many complications can be slowed or even prevented with strict control of blood sugar levels.
 See the sidebar The Foot in Diabetes.
See the sidebar More About Insulin.
 See the table Long-Term Complications of Diabetes.
See the table Oral Antihyperglycemic Drugs.
 See the figure How Long Different Types of Insulin Work.
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