Patients with diabetes have higher death rates than people who do not have diabetes regardless of sex, age, or other factors. Heart disease and stroke are the leading causes of death in these patients. All lifestyle and medical efforts should be made to reduce the risk for these conditions.
People with type 2 diabetes are also at risk for nerve damage (neuropathy) and abnormalities in both small and large blood vessels (vascular injuries) that occur as part of the diabetic disease process. Such abnormalities produce complications over time in many organs and structures in the body. Although these complications tend to be more serious in type 1 diabetes, they still are of concern in type 2 diabetes.
There is an association between high blood pressure (hypertension), unhealthy cholesterol levels, and diabetes. People with diabetes are more likely than non-diabetics to have heart problems, and to die from heart complications. Heart attacks account for 60% and strokes for 25% of deaths in patients with diabetes. Diabetes affects the heart in many ways:
- Both type 1 and 2 diabetes speed the progression of atherosclerosis (hardening of the arteries). Diabetes is often associated with low HDL ("good" cholesterol) and high triglycerides. This can lead to coronary artery disease, heart attack, or stroke.
- High blood pressure is more common in patients with diabetes than those without the condition.
- Impaired nerve function (neuropathy) associated with diabetes may also lead to cardiovascular problems.
- Women with diabetes are at particularly high risk for heart problems and death from heart disease and overall causes.
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.
Diabetic nephropathy is the leading cause of end-stage renal disease (ESRD).. If the kidneys fail, dialysis is required. Symptoms of kidney failure may include swelling in the feet and ankles, itching, fatigue, and pale skin color.
|Click the icon to see an image of the pancreas and kidneys.|
Nerve Disorders (Neuropathy)
Diabetes reduces or distorts nerve function, causing a condition called neuropathy. Neuropathy refers to a group of disorders that affect nerves. The two main types of neuropathy are:
- Peripheral (affects nerves in the toes, feet, legs, hand, and arms)
- Autonomic (affects nerves that help regulate digestive, bowel, bladder, heart, and sexual function)
Peripheral neuropathy particularly affects sensation. It is a common complication for nearly half of people who have lived with type 1 or type 2 diabetes for more than 25 years. The most serious consequences of neuropathy occur in the legs and feet and pose a risk for ulcers and, in unusually severe cases, amputation. Peripheral neuropathy usually starts in the fingers and toes and moves up to the arms and legs (called a stocking-glove distribution). Symptoms include:
- Burning sensations
- Loss of the sense of warm or cold
- Numbness (if the nerves are severely damaged, the patient may be unaware that a blister or minor wound has become infected)
- Deep pain
Autonomic neuropathy can cause:
- Digestive problems (constipation, diarrhea, nausea, vomiting)
- Bladder infections and incontinence
- Erectile dysfunction
- Heart problems. Neuropathy may mask angina, the warning chest pain for heart disease and heart attack. Patients with diabetes should be aware of other warning signs of a heart attack, including sudden fatigue, sweating, shortness of breath, nausea, and vomiting.
- Rapid heart rates
- Lightheadedness when standing up (orthostatic hypotension)
Heart disease risk factors may increase the likelihood of developing neuropathy. Lowering triglycerides, losing weight, reducing blood pressure, and quitting smoking may help prevent the onset of neuropathy.
Foot Ulcers and Amputations
About 15% of patients with diabetes have serious foot problems. They are the leading cause of hospitalizations for these patients.
Diabetes is responsible for more than half of all lower limb amputations performed in the U.S. Most amputations start with foot ulcers.
Those most at risk are people with a long history of diabetes, and people with diabetes who are overweight or who smoke. People who have the disease for more than 20 years and are insulin-dependent are at the highest risk. Related conditions that put people at risk include peripheral neuropathy, peripheral artery disease, foot deformities, and a history of ulcers. [For more information, see In-Depth Report #102: Peripheral artery disease and intermittent claudication.]
Foot ulcers usually develop from infections, such as those resulting from blood vessel injury. Foot infections often develop from injuries, which can dramatically increase the risk for amputation. 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 a third of foot ulcers occur on the big toe.
Charcot Foot. Charcot foot or Charcot joint (medically referred to as neuropathic arthropathy) is a degenerative condition that affects the bones and joints in the feet. It is associated with the nerve damage that occurs with neuropathy. Early changes appear similar to an infection, with the foot becoming swollen, red, and warm. Gradually, the 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 normal activity, causing further damage.
Retinopathy and Eye Complications
Diabetes accounts for thousands of new cases of blindness annually and is the leading cause of new cases of blindness in adults age 20 - 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, such as primary-open angle glaucoma (POAG). The risk for POAG is especially high for women with type 2 diabetes. [For more information, see In-Depth Report #26: Cataracts and In-Depth Report #25: Glaucoma.]
Retinopathy is a condition in which the retina in the eye becomes damaged. Retinopathy generally occurs in one or two phases:
|Click the icon to see an image of diabetic retinopathy.|
- The early and more common type of this disorder is called nonproliferative or background retinopathy. The blood vessels in the retina are abnormally weakened. They rupture and leak, and waxy areas may form. If these processes affect the central portion of the retina, swelling may occur, causing reduced or blurred vision.
- If the capillaries become blocked and blood flow is cut off, soft, "woolly" areas may develop in the retina's nerve layer. These woolly areas may signal the development of proliferative retinopathy. In this more severe condition, new abnormal blood vessels form and grow on the surface of the retina. They may spread into the cavity of the eye or bleed into the back of the eye. Major hemorrhage or retinal detachment can result, causing severe visual loss or blindness. The sensation of seeing flashing lights may indicate retinal detachment.
|Click the icon to see an animation on diabetic retinopathy.|
Mental Function and Dementia
Some studies indicate that patients with type 2 diabetes, especially those who have severe instances of low blood sugar, face a higher than average risk of developing dementia. Diabetes can also cause problems with attention and memory.
Respiratory Infections. People with diabetes face a higher risk for influenza and its complications, including pneumonia. Everyone with diabetes should have annual influenza vaccinations 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. Depression, in turn, may increase the risk for hyperglycemia and complications of diabetes.
Tight blood sugar (glucose) control increases the risk of low blood sugar (hypoglycemia). Hypoglycemia, also called insulin shock, occurs if blood glucose levels fall below normal. It is generally defined as blood sugar level below 70 mg/dL, although this level may not necessarily cause symptoms in all patients. Hypoglycemia may also be caused by insufficient intake of food, or excess exercise or alcohol. Usually the condition is manageable, but occasionally, it can be severe or even life threatening, particularly if the patient fails to recognize the symptoms, especially while continuing to take insulin or other hypoglycemic drugs.
Mild hypoglycemia is common among people with type 2 diabetes, but severe episodes are rare, even among those taking insulin. Still, all patients who intensively control blood sugar (glucose) levels should be aware of warning symptoms.
Hypoglycemia Symptoms. Mild symptoms usually occur at moderately low and easily correctable levels of blood glucose. They include:
- Rapid heartbeat
Severely low blood glucose levels can cause neurologic symptoms such as:
- In rare and worst cases, coma, seizure, and death
[For information on preventing hypoglycemia or managing an attack, see Home Management section of this report.]
Diabetic Ketoacidosis (DKA)
Diabetic ketoacidosis (DKA) is a life-threatening complication caused by insulin deficiency. Until recently, it was a complication almost exclusively of type 1 diabetes. In such cases, it is nearly always due to noncompliance with insulin treatments. However, in rare cases DKA can also occur in patients with type 2 diabetes.
Diabetes increases the risk for developing other conditions, including:
- Hearing loss
- Periodontal disease
- Carpal tunnel syndrome
- Nonalcoholic fatty liver disease, also called nonalcoholic steatohepatitis (NASH), a particular danger for people who are obese
- Colorectal cancer
- Uterine cancer
Specific Complications in Women
Diabetes can cause specific complications in women. Women with diabetes have an increased risk of recurrent yeast infections. In terms of sexual health, diabetes may cause decreased vaginal lubrication, which can lead to pain or discomfort during intercourse.
Women with diabetes should also be aware that certain types of medication can affect their blood glucose levels. For example, birth control pills can raise blood glucose levels. Long-term use (more than 2 years) of birth control pills may increase the risk of health complications. Thiazolidinediones can prompt renewed ovulation in premenstrual women who are not ovulating, and can weaken the effect of birth control pills.
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 high blood sugar levels (hyperglycemia) can affect the developing fetus during the critical first 6 weeks of organ development. Therefore, it is important that women with pre-existing diabetes (both type 1 and type 2) who are planning on becoming pregnant strive to maintain good glucose control for 3 - 6 months before pregnancy. It is also important for women to closely monitor their blood sugar levels during pregnancy. For women with type 2 diabetes who take insulin, pregnancy can affect their insulin dosing needs. Insulin dosing may also need to be adjusted during and following delivery.
Diabetes and Menopause. The changes in estrogen and other hormonal levels that occur during perimenopause can cause major fluctuations in blood glucose levels. Women with diabetes also face an increased risk of premature menopause, which can lead to higher risk of heart disease.
Review Date: 04/01/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.