Diabetes: Type 1
DescriptionAn in-depth report on the causes, diagnosis, and treatment of type 1 diabetes.
Alternative NamesInsulin-dependent Diabetes Mellitus; Juvenile Diabetes
Type 1 diabetes reduces the normal life span by an average of five to eight years. In general, however, survival rates are improving in all ethnic groups and both genders. Longer survival rates are probably due to improvements in monitoring and closer control of blood glucose. There are two important approaches to preventing complications from type 1 diabetes:
Complications of Heart and Circulation
Heart attacks account for 60% and strokes for 25% of deaths in all diabetics. Diabetes effects the heart in many ways:
Intensive blood sugar control may help protect blood vessels and reduce the risk for blood clotting. It is still not known whether intensive control will have a major protective effect on the heart, however. People with diabetes must be sure to use other measures as well to protect the heart.
Aspirin for Reducing the Risk for Blood Clots. Taking a daily aspirin reduces the risk for blood clotting and has been shown to be protective against heart attacks. In one 2000 study, low-dose aspirin was associated with a 30% lower risk for death from heart disease in adults with type 2 diabetes. Of note: people who are at risk for retinopathy should discuss the possible benefits of high-dose aspirin with their physician.
Reducing Blood Pressure. Strict control of blood pressure is critical for preventing complications of diabetes and has proven to improve survival rates. Patients should strive for blood pressure levels of less than 130/80 mm Hg (systolic/diastolic). (Controlling systolic pressure may be especially important for reducing the risk for kidney complications.)
Anti-hypertensive agents that block angiotensin are the first option for may people with diabetes. Angiotensin is natural chemical that influences all aspects of blood pressure control and also interferes with insulin's normal metabolic signaling. In fact, angiotensin may be the common factor linking diabetes and high blood pressure. Drugs that block them are ACE inhibitors and ARBs:
Combinations of the two are under investigation, and studies suggest such combinations may be beneficial for people with diabetes and kidney disease.
Other anti-hypertensive agents may be important for specific groups. Diuretics appear to be more beneficial than ACE inhibitors for African Americans with diabetes. In one major study, these patients had lower rates of stroke and heart failure than those taking ACE inhibitors. Beta blockers, another group of anti-hypertensive agents, may have more benefits for patients with existing heart disease, although more research is needed to confirm this.
[For more information, seeWell-Connected Report #14 High Blood Pressure.]
Improving Cholesterol and Lipid Levels. Abnormal cholesterol and lipid levels are common in diabetes. High LDL cholesterol should always be lowered, but people with diabetes also often have additional harmful imbalances--low-HDL cholesterol and high triglycerides. Patients should aim for LDL levels below 100 mg/dl, HDL levels over 60 mg/dL and triglyceride levels below 150 mg/dL.
Statins are currently the best cholesterol-lowering agents for people with diabetes. They include pravastatin (Pravachol), simvastatin (Zocor), fluvastatin (Lescol), and atorvastatin (Lipitor). These agents are very effective for lowering LDL cholesterol levels. In addition, evidence suggests that statins reduces the risk for adverse heart events in people with even mild diabetes and in those with normal cholesterol levels. Furthermore, in one study, a statin was shown to reduce the risk by 30% of developing diabetes in people with high cholesterol. (Statins, however, do not appear to have any effect on blood vessel inflexibility in diabetes, which is an important risk factor for heart disease in these patients.) The primary safety concern with statins in people with diabetes has involved myopathy, an uncommon condition that can cause muscle damage and, in some cases, muscle and joint pain. A specific myopathy called rhabdomyolysis can lead to kidney failure. People with diabetes and risk factors for myopathy should be monitored for muscle symptoms.
Although lowering LDL is beneficial, statins are not as effective as other medications, such as fibrates or niacin, in addressing HDL and triglyceride imbalances--a common problem in type 2 diabetes.
Combinations of statins with one these agents, then, may be important in people with diabetes. Although combinations of statins and fibrates or niacin increase the risk of myopathy, both combinations are considered safe if used with extra care.
Fibrates, such as fenofibrate (Tricor) and bezafibrate (Bezalip), are usually the first choice. Niacin has the most favorable effect on HDL and triglycerides of all the cholesterol drugs. However, about 30% of patients who take niacin experience elevated blood glucose levels. On the positive side, some studies have reported that diabetics who use niacin had little trouble with glucose control. In addition, niacin-statin therapy reduces the progression of heart disease. Some experts believe it now may be used as an alternative to or in combination with statins. Combinations with a new agent ezetimibe (Zetia) may also be beneficial. Ezetimibe inhibits the absorption of cholesterol in the intestines and is proving to be a very useful adjunct to statins for lowering LDL levels.
[For more information, seeWell-Connected Report #23 Cholesterol, Other Lipids, and Lipoproteins.]
Kidney Damage (Nephropathy)
Kidney disease (nephropathy) is a very serious complication of diabetes. With this condition, the tiny filters in the kidney (called glomeruli) become damaged and leak protein into the urine. Over time this can lead to kidney failure. Urine tests showing microalbuminuria (small amounts of protein in the urine) are important markers for kidney damage.
Treatment and Prevention of Nephropathy. Long-term studies are now reporting a 60% reduction in new cases of nephropathy with strict blood glucose control and a delay in progression of the disease. Targeting specific preventive measures may especially protect against kidney disease. They include maintaining glycolated hemoglobin levels at 7% or below, controlling blood pressure--particularly systolic pressure, and lowering not only LDL cholesterol but also triglycerides.
The antihypertensive drugs ACE inhibitors are proving to protect against progression of kidney disease even in people with normal blood pressure. They are now the agents of choice for both preventing and managing nephropathy in type 1 diabetes. Newer agents called angiotensin-IIreceptor blockers (ARBs), such as losartan (Cozaar) and irbesartan (Avapro), are also helpful for both conditions.
Sulodexide is an agent based on a natural substance called a glycosaminoglycan, which helps reduce blood clotting. Studies are suggesting that it may help prevent nephropathy with few side effects. (It also may be helpful for foot ulcers.)
If the kidneys fail, the patient will need to go on dialysis. Symptoms of kidney failure may include swelling in the feet and ankles, itching, fatigue, and pale skin color.
Diabetes reduces or distorts nerve function causing a condition called neuropathy. It particularly affects sensation. It is a common complication that affects nearly half of both type 1 and type 2 diabetics after 25 years. Neuropathy usually starts in the fingers and toes and moves up to the arms and legs (called a stocking-glove distribution). Symptoms include the following:
The most serious consequences of neuropathy affect the legs and feet and pose a risk for ulcers and, in very severe cases, amputation. In some cases, neuropathy may mask angina, the warning chest pain for heart disease and heart attack. Diabetic patients should be aware of other warning signs of a heart attack, including sudden fatigue, sweating, shortness of breath, nausea, and vomiting.
Neuropathy Pain and its Treatment. Studies show that tight control of blood glucose levels also delays the onset and slows progression of neuropathy, although there is some concern that the increased incidence of hypoglycemia with intensive insulin control may actually cause nerve damage.
A number of agents are used for neuropathy depending on its effects. Some used for neuropathy pain include the following:
Other Complications of Neuropathy. Neuropathy also affects other functions and treatments are needed to reduce their effects as well. If diabetes affects the nerves in the autonomic nervous system, then abnormalities of blood pressure control and bowel and bladder function may occur. Erythromycin, domperidone (Motilium), or metoclopramide (Reglan) may be used to relieve delayed stomach emptying caused by neuropathy.
Impotence in men is also associated with neuropathy. Sildenafil (Viagra), vardenafil (Levitra, Nuviva, and tadalafil (Cialis)) are proving to be effective treatments for impotence in about half of the men with either type 1 or type 2 diabetes. Side effects and usually minimal.
Foot Ulcers and Amputations. Perhaps the most serious consequences of diabetic neuropathy occur in the lower limbs. An estimated 15% of diabetics experience serious foot problems. They are the leading cause of hospitalizations for these patients.
Diabetes is responsible for more than half of all the lower limb amputations performed in the U.S. Each year there are about 88,000 non-injury amputations and between 50% and 75% of them are due to diabetes. Worse, the number is increasing as the prevalence in diabetes type 2 rises. About 85% of amputations start with foot ulcers, which develop in about 12% of people with diabetes.
In general, foot ulcers develop from infections, such as those resulting from blood vessel injury. Even minor infections can develop into severe complications. Numbness from nerve damage, which is common in diabetes, compounds the danger since the patient may not be aware of injuries. About one-third of foot ulcers occur on the big toe.
According to a 2003 government survey, those at higher risk for foot ulcers tend to be people with diabetes who are overweight, smokers, and those with a long history of diabetes. People who had had the disease for more than 20 years and were insulin-dependent were at the highest risk. Related conditions that put people at risk include peripheral neuropathy, peripheral arterial disease, foot deformities, and a history of ulcers.
Charcot Foot. Charcot foot or Charcot joint (medically referred to as neuropathic arthropathy) occurs in up to 2.5% of people with diabetes. Early changes appear like an infection, with the foot becoming swollen, red, and warm. A seriously affected foot can become deformed. The bones may crack, splinter, and erode, and the joints may shift, change shape, and become unstable. It typically develops in people who have neuropathy to the extent that they cannot feel sensation in the foot and are not aware of an existing injury. Instead of resting an injured foot or seeking medical help, the patient often continues to normal activity, causing further damage.
Charcot foot is initially treated with strict immobilization of the foot and ankle; some centers use a cast that allows the patient to move and still protects the foot. A 2001 study in the U.K. concluded that a single dose of pamidronate, a bisphosphonate, reduces bone turnover, symptoms, and disease activity. When the acute phase has passed, patients usually need lifelong protection of the foot using a brace initially and custom footwear.
Measures to Prevent Foot Ulcers. Preventive foot care could significantly reduce the risk of ulcers and amputation. Some tips for preventing problems include the following:
Treating Foot Ulcers in Diabetes. About one-third of foot ulcers will heal within 20 weeks with good wound care treatments. Some treatments are as follows:
Investigative Agents for Treating Foot Ulcers. A number of recent investigative agents and procedures for treating foot ulcers include the following:
Devices to Heal Ulcers and Protect the Foot. Researchers are also using or investigating various devices to heal or prevent ulcers. The following are some examples:
Retinopathy and Eye Complications
Diabetes accounts for 12,000 to 24,000 of new cases of blindness annually and is the leading cause of new cases of blindness in adults ages 20 to 74. The most common eye disorder in diabetes is retinopathy. People with diabetes are also at higher risk for developing cataracts and certain types of glaucoma. [For more information, seeWell-Connected Report #26 Cataractsor Report #25 Glaucoma.]
Description of Retinopathy. Retinopathy is a condition in which the retina becomes damaged. The two primary abnormalities that occur are a weakening of the blood vessels in the retina and the obstruction in the capillaries--probably from very tiny blood clots. Retinopathy generally occurs in one or two phases:
According to a 2003 study, about 40% of young adults with type 1 diabetes had developed retinopathy within 10 years of diagnosis. (Although this rate is high, it is significantly lower than in previous years when blood glucose control was not as strict.) The risk is lower in patients with type 2, although in one study over 20% had signs of retinopathy six years after diagnosis. Any patient on insulin or who has had diabetes for more than 20 years should have a yearly eye examination. Patients with no signs of retinal damage or risk factors for retinopathy may only require screening every three years.
Prevention of Retinopathy. Fortunately, severe and even moderate vision loss is largely preventable with intensive control of blood glucose levels. (Note: intense glucose control can cause early worsening of retinopathy, although this is nearly always counterbalanced by long-term benefits.) Measures for reducing risks to the heart (e.g., ACE inhibitors for lower blood pressure and drugs that improve cholesterol) may also have protective benefits for the eyes. Whereas low-dose aspirin is used to prevent heart disease, high doses may prevent retinopathy. Patients at risk for retinopathy should discuss this therapy with their physicians.
Treatment of Retinopathy. Once damage to the eye develops, eye surgery may be needed. Argon or diode laser photocoagulation is proving to be particularly effective in reducing severe visual loss from retinopathy, and is useful for patients with macular edema when fluid build-up threatens the retina.
Mental Function and Dementia
Studies indicate that patients with type 2 diabetes face a higher than average risk of developing dementia caused either by Alzheimer's disease or problems in blood vessels in the brain. Problems in attention and memory can occur even in people under age 55 who have had diabetes for a number of years. In one study of people with type 1 diabetes, high glucose levels (hyperglycemia) were associated with slower brain function, including less verbal fluency and slow ability to do mental arithmetic.
Respiratory Infections. People with diabetes face a higher risk for influenza and its complications, including pneumonia, possibly because the disorder neutralizes the effects of protective proteins on the surface of the lungs. In fact, deaths among people with diabetes increase by 5% to 15% during flu epidemics and they are six times more likely to be hospitalized with complications from flu than nondiabetics who have flu. Everyone with diabetes should have influenza vaccinations annually and a vaccination against pneumococcal pneumonia.
Urinary Tract Infections. Women with diabetes face a significantly higher risk for urinary tract infections, which are likely to be more complicated and difficult to treat than in the general population.
Diabetes doubles the risk for depression. Furthermore, according one study, depression, in turn, increases the risk for hyperglycemia and complications of diabetes. Restoring mental health, both through medication and psychotherapy, not only improves quality of life but also helps patients control their blood sugar levels.
Changes in Bone Quality
Diabetes changes bone quality and density, but the effects differ depending on type:
Older patients with either type are at risk for falling, which compounds the risk for fracture.
Other complications of diabetes include the following:
Specific Complications in Women
Diabetes and Pregnancy. Both temporary diabetes that occurs during pregnancy (gestational diabetes) and pregnancy in a patient with existing diabetes can increase the risk for birth defects. Studies indicate that hyperglycemia may effect the developing fetus as soon as it is conceived.
Because glucose crosses the placenta, a woman with diabetes can pass high levels of blood glucose to the fetus. In response, the fetus secretes large amounts of insulin. This combination of high fetal blood levels of insulin and glucose can have significant effects:
In addition to endangering the fetus, diabetes also presents risks to the pregnant woman, particularly preeclampsia, which is a potentially dangerous condition involving very high blood pressure. Pregnant women with diabetes are also at greater risk for retinopathy.
Some suggestions for preventing complications include the following:
Of note: Although there was some concern that short-acting insulin lispro might increase the risk for birth defects, the most recent evidence suggests that it does not. In fact, some experts believe it achieves a better outcome and should be preferred to regular insulin in pregnant women. More research is needed.
Effect on Estrogen. Diabetes appears to blunt some of the effects of estrogen, which may increase the risk for heart disease. Women with diabetes have a higher risk for early menopause, which, in one study, occurred at an average age of about 41 years.
Reproductive Cancers. Women with type 1 diabetes often have lumps in the breast that are benign but which make mammograms difficult to interpret. It is not clear whether these lumps are risk factors for breast cancer. One study indicated that women with diabetes have a higher risk for endometrial cancer and possibly for breast cancer.
Specific Problems in Adolescents with Type 1 Diabetes
Lack of Blood Glucose Control. Control of blood glucose levels is generally very poor in adolescents and young adults. Adolescents with diabetes are at higher risk than adults for ketoacidosis resulting from noncompliance. In a British study of young adults with type 1 diabetes, 15% were already hypertensive and about half of these young people had signs of kidney damage. Young people who do not control glucose are also at high risk for permanent damage in small vessels, such as those in the eyes.
Self-Destructive Behaviors. One study found that young people with diabetes have a higher than average rate of suicidal fantasies. Although the actual rate of suicide was no higher than that of their nondiabetic peers, such thoughts are strongly associated with self-destructive behavior.
Of particular note, up to one-third of young women with type 1 diabetes have eating disorders and underuse insulin to lose weight. Anorexia and bulimia pose significant health dangers in any young person--but they can be especially severe in people with diabetes.