Atherosclerosis and Diabetes

Atherosclerosis and Diabetes

Summary

Atherosclerosis is a disease in which fatty plaque gradually forms on the inner walls of the arteries. This disorder, also known as hardening of the arteries, causes the arteries to become narrow and restricts the blood flow to organs and tissues.

Diabetes increases the risk for atherosclerosis and other cardiovascular complications partly because of excess glucose (blood sugar). This hyperglycemia damages arteries by making the walls thicker and less elastic. The change makes it more difficult for the blood to pass through the vessels.

Atherosclerosis increases the risk of heart attack, in which blockages within the coronary arteries prevent blood from reaching the heart. Similarly, atherosclerosis can cause cerebrovascular disease, which restricts blood flow to the brain and increases the risk of stroke. Atherosclerosis can affect other parts of the body such as the legs, and contributes to the development of peripheral arterial disease.

However, there are a number of things that people with diabetes can do to prevent atherosclerosis, including:

  • Controlling cholesterol, blood pressure, glucose and weight
  • Getting regular exercise
  • Not smoking

Treatment of atherosclerosis may include lifestyle changes, medications or surgical procedures.

About atherosclerosis

Atherosclerosis, also known as hardening of the arteries, is a disease in which the arteries become narrowed and hardened as a result of a gradual buildup of plaque within the arteries. Atherosclerosis is the most common form of arteriosclerosis, a group of diseases in which the arteries become thick and hard. Although these terms are used interchangeably, atherosclerosis refers to hardening of medium and large arteries by the buildup of fat.

Normally, blood flows through the arteries, delivering oxygen and nutrients from the heart to the rest of the body. Healthy arteries are flexible and strong. With time, however, the arteries can become stiff and narrow, restricting the blood flow to organs and tissues. Tissues and cells in the body become damaged and may die without adequate blood supply.

Although some hardening of the arteries occurs naturally with age, atherosclerosis involves the buildup of plaque, composed of cholesterol (lipoproteins), calcium and other materials. Atherosclerosis is a slow, complex disease that typically starts with the appearance of fatty streaks around the aorta.

Narrowed arteries from atherosclerosis can reduce the blood supply to vital organs, such as the heart and brain. In addition, the plaque can rupture, causing larger blood clots to form that can block blood flow or travel to another part of the body.

Atherosclerosis is a major cause of death and disability in the United States, as it is the underlying problem in serious conditions including coronary artery disease, heart attack and stroke.

In addition to raising the risk of cardiovascular disease, atherosclerosis can contribute to other diabetic complications by impeding circulation. These include skin disorders, foot problems and impaired healing of wounds such as ulcers.

Individuals with diabetes are at increased risk of developing atherosclerosis for several reasons:

  • High levels of glucose (blood sugar) make the blood vessels thicker and less elastic. It is more difficult for blood to pass through these arteries.
  • This excess glucose (hyperglycemia) contributes to higher levels of fats in the blood. People with diabetes tend to have more fats (lipids) in their blood, which narrow and clog the arteries.
  • People with type 2 diabetes, by far the most common form of diabetes, often have additional risk factors for atherosclerosis. These include high blood pressure, obesity and hyperlipidemia (unhealthy levels of blood fats).

In addition, research indicates that insulin resistance, which is a feature in prediabetes, type 2 diabetes and double diabetes, may contribute to the development of atherosclerosis. It is not clear how insulin resistance is related to this disease, but it is thought to be through direct and indirect conditions. Directly, insulin resistance may change the composition and structure of the walls of the arteries. Indirectly, insulin resistance is associated with dyslipidemia (high levels of “bad” LDL cholesterol and low levels of “good” HDL cholesterol). This condition often occurs in individuals with early coronary artery disease.

According to the U.S. Centers for Disease Control and Prevention (CDC), individuals with diabetes are two to four times more likely to have heart disease than persons without diabetes. Further, the risk of stroke is about twice as likely in diabetes patients. Cardiovascular disease is the leading cause of death in patients with diabetes.

It is difficult, if not impossible, to determine the number of people who have atherosclerosis. The condition does not have outward symptoms and may not be detected until an artery is seriously damaged.  The American Heart Association (AHA) estimated in 2005 that atherosclerosis caused about 14,000 deaths annually in the United States, contributed to about 69,000 deaths and accounted for nearly three-fourths of deaths from cardiovascular disease, which is the leading cause of death in the United States. The AHA did not release estimates of these statistics in 2006.

Much research is being done on atherosclerosis. Recent highlights include:

  • Though atherosclerosis is commonly associated with middle and old age, metabolic syndrome, a cluster of conditions that can include diabetes, has been found to be an important indicator of silent (subclinical) atherosclerosis in young adults.
  • As researchers learn more about the role of inflammation in atherosclerosis, they are working toward creating a vaccine that might regulate the body’s inflammatory response, thus reducing atherosclerosis in high–risk patients.
  • Studies have indicated anti-inflammatory properties in a class of cholesterol-reducing drug called statins. Fibrates, another type of cholesterol drug, have been found to decrease the progression of coronary artery disease and atherosclerosis in patients with type 2 diabetes.
  • Studies have shown that antihypertensives decrease signs of inflammation in the blood, suggesting that these blood pressure drugs may also slow the inflammatory changes that lead to atherosclerosis.
  • Certain foods have shown promise in slowing or reversing atherosclerosis. These include walnuts, which contain monounsaturated fats, and moderate consumption of red wine, which contains an antioxidant called resveratrol. Experts, however, do not recommend consuming red wine or any alcohol strictly for potential cardio–protective benefits, and diabetic patients need clearance from their physician before drinking alcohol because it can alter control of glucose.
  • The Diabetes Heart Study, a large-scale project in North Carolina, found that diabetic black men had much less atherosclerosis than diabetic white men. The surprising finding is believed to be due to biological or genetic differences.

Risk factors and causes

There are two main theories as to the cause of atherosclerosis:

  • Unhealthy levels of cholesterol in the blood damage the walls of the arteries. The cholesterol causes an inflammatory reaction that allows fatty materials to accumulate.
  • Repeated injury to the walls of the artery from the immune system or direct toxicity.  

In both of these theories, there is a change in the arteries that leads to the development of fatty materials, known as atheromas. It is believed that these theories are not completely separate and are most likely related to each other in the cause of the disease.

Atherosclerosis is also thought to involve inflammation as certain white blood cells are present during the development of the disease. These cells move out of the bloodstream into the artery walls, where they are transformed into foam cells. These foam cells collect cholesterol and other fatty materials which in turn form atheromas. The atheromas cause a hardening and thickening of the artery wall.

Hardening of the arteries occurs over time, which means the older a person is the greater the risk for developing the disease.  Most cases of atherosclerosis are found in middle–age and older adults. Men and individuals with a family history of premature cardiovascular diseases have an increased risk of atherosclerosis.

There are several additional conditions that increase the risk of developing atherosclerosis. Some of the risk factors can be controlled, such as diet, but others cannot be controlled, such as family history.

Diabetes is one such disease that increases the risk of atherosclerosis. Researchers believe that higher glucose levels damage blood vessels, creating a greater likelihood of developing cardiovascular problems. Characteristics for diabetes and atherosclerosis include:

  • People with type 1 diabetes may be more likely to develop arteriosclerosis in the small arteries, such as those in the eyes and the kidneys, and sometimes in the large arteries.
  • People with type 2 diabetes are more likely to develop atherosclerosis in the large arteries, such as in the heart.

People with diabetes tend to develop atherosclerosis at an earlier age and more extensively than those individuals without diabetes. The risk of developing atherosclerosis is 2 to 6 times higher for people with diabetes.

Additionally, individuals with diabetes may have a number of related factors that increase the risk for atherosclerosis. These risk factors include:

  • High blood pressure. This condition has long been recognized as a major risk factor for atherosclerosis and cardiovascular disease. When a person has high blood pressure and diabetes, a common combination, the risk for cardiovascular disease doubles.
  • Dyslipidemia. High levels of LDL “bad” cholesterol and triglyceridesand low levels of HDL “good” cholesterol contribute to the development of atherosclerosis. Dyslipidemia is frequently present in diabetes patients.
  • Obesity. Being significantly overweight greatly increases the risk of cardiovascular disease. Abdominal obesity is closely associated with type 2 diabetes as well as high blood pressure and high cholesterol, leading to atherosclerosis.
  • Smoking. Research has documented that tobacco smoking contributes to cardiovascular disease. Smoking has been shown to:
    • Decrease HDL cholesterol
    • Increase LDL cholesterol
    • Damage artery walls with increased carbon monoxide in the blood
    • Constrict arteries, further limiting the blood flow
    • Increase the blood’s tendency to clot by making platelets stickier
  • Physical inactivity. Inactivity appears to increase the risk of cardiovascular disease, whereas regular exercise appears to reduce the risk. In addition, a sedentary lifestyle is often associated with diabetes and high blood pressure.
  • Homocysteine. This amino acid in the blood injures the artery walls and increases the formation of atheromas (collections of plaque). People with that suspected hereditary disorder often develop extensive atherosclerosis at an early age. It is not a condition known to be associated with diabetes.
  • Stress. Some research suggests that factors such as stress, hostility and marital discord may contribute to atherosclerosis.

The risk factors for atherosclerosis are clearly related to one another. An increase in weight can cause an increase in cholesterol and blood pressure. In addition, many of the associated risk factors are commonly found in people with diabetes. With each of these factors, a diabetic person has a greater chance of developing atherosclerosis and cardiovascular complications.

Signs and symptoms of atherosclerosis

The symptoms of atherosclerosis usually appear gradually and may not become evident until there is serious damage to an artery. Symptoms may not appear until the wall of the artery is narrowed by more than 70 percent. The symptoms vary according to the location and severity of the blockage. Atherosclerosis can affect any arteries in the body but most often occurs in the arteries serving the heart, brain, legs and kidneys.

At first, symptoms may occur only after vigorous exertion when the arteries cannot supply the oxygen and nutrients demanded by the tissues. As the narrowing becomes worse, it takes less and less exertion for the symptoms to appear. The more the artery is blocked, the more serious the symptoms. For example, if an artery leading to the heart (coronary artery) is narrowed, the individual may feel a type of chest pain called angina. However, if the artery is blocked, it can cause a heart attack (myocardial infarction).  In some cases, people do not recognize the first signs of atherosclerosis, resulting in a more serious consequence.

In individuals with diabetes, a common symptom of atherosclerosis is intermittent pain or cramping in the legs, known as claudication. Obstruction of the arteries in the legs may cause this symptom, which is an indication of a more serious condition, peripheral artery disease (PAD). Claudication is associated with a two– to three–fold increase in risk of stroke, heart failure or coronary heart disease in men with diabetes, according to the American Diabetes Association (ADA). Left untreated, PAD can result in complications including unhealing ulcers, infections, gangrene and amputation.

Other symptoms that may appear as the result of atherosclerosis in different areas include:

  • Neck. Possible signs of cerebrovascular disease include headache or impaired memory. Obstructions of the carotid arteries in the neck may cause symptoms of a “mini-stroke” (transient ischemic attack, TIA) or stroke, such as sudden numbness or weakness, dizziness or difficulty communicating.
  • Abdomen. Obstruction of the abdominal aorta usually does not have symptoms before the dangerous signs of rupture. Occasionally, individuals may note a pulsating abdominal mass.
  • Arms. As with PAD in the legs, atherosclerosis may cause pain or cramping in the arms.
  • Genitals. Atherosclerosis may cause erectile dysfunction in men.

In some cases, atherosclerosis may cause a change in the appearance of the skin, particularly on the legs. The skin becomes hairless, thin, cool and shiny. In addition, the feet may have thick and discolored toenails. The toes may become cold because of a poor blood supply to that region.

Because blood carries the white cells that fight infections, individuals with atherosclerosis may have difficulty healing from injuries. Even minor scrapes and cuts can advance to open sores that heal slowly. This symptom is particularly dangerous to individuals with diabetes as diabetic neuropathy (nerve damage) may prevent them from feeling the injuries and obtaining early medical treatment.

Diagnosis methods for atherosclerosis

The first signs of atherosclerosis may be found during a routine physical examination by a physician. Prior to the examination, the physician will obtain a medical history with emphasis on risk factors, such as:

  • Family history of cardiovascular problems
  • Type and duration of diabetes
  • Past levels of glucose and cholesterol
  • History of blood pressure problems
  • Smoking and use of alcohol
  • Diet and exercise habits
  • Symptoms of artery damage, such as chest pain, muscle cramping or numbness

In the examination, the physician will look for indications of narrowed or hardened arteries, including:

  • Whooshing sounds (bruits) heard by a stethoscope when listening to the arteries
  • Weak or absent pulse below the narrowed part of the artery
  • Evidence of poor healing of a wound or sore in the areas where restricted blood flow is suspected
  • Decreased blood pressure in an affected arm, leg or foot
  • Signs of pulsing bulge (aneurysm) in the abdomen or behind the knee

To help diagnose atherosclerosis, the physician may recommend several tests, including:

  • Blood tests. A blood test can be used to check for increased levels of cholesterol,glucose or homocysteine, which are risk factors for the disease.
  • Ankle brachial index (ABI). This test uses a blood pressure cuff and a Doppler ultrasound device to measure blood flow. The physician measures and compares the blood pressure between the arm and ankle. The normal range is 0.95 to 1.2.  If the ABI measurement does not fall within that normal range, it indicates peripheral artery disease, which is usually caused by atherosclerosis.
  • Electrocardiogram (EKG). An electrocardiogram measures the electrical impulses from the heart through electrode patches attached to the skin. It can help detect heart problems. An exercise stress test, in which an EKG is performed while the patient uses a treadmill or stationary bicycle, may also be recommended, with or without a harmless nuclear contrast medium.
  • Doppler ultrasound. This test allows a physician to see arteries throughout the body. It also allows blood pressure to be measured at various points along the arm or leg to determine any blockage in the arteries. An ultrasound of the heart is called an echocardiogram
  • Other imaging tests. Chest x-rays, CAT scan (computed axial tomography) and MRI (magnetic resonance imaging) allow a physician to view the arteries. They can help determine the presence and extent of blockage. These tests often show hardening and narrowing of large arteries, calcium deposits and aneurysms. A new form of CAT scan, called multi–detector computed tomography (MDCT), has shown advantages over the traditional electron beam computed tomography (EBCT) in detecting atherosclerosis.
  • Angiography. If advanced atherosclerosis is suspected, a physician may perform a coronary or carotid angiogram, a type of arterial x-ray. A thin tube (catheter) is threaded through a blood vessel, usually the femoral artery in the upper thigh, and guided to the coronary arteries of the heart or a carotid artery in the head. The physician then injects a dye (contrast medium) through the catheter to enhance x-rays. In some cases, coronary blockages can be treated immediately through the catheter while it is still in place.

Treatment and prevention methods

Lifestyle changes may be one of the first steps in the treatment of atherosclerosis. This treatment also may decrease the severity of or prevent atherosclerosis in the future. Lifestyle changes are particularly important to individuals with diabetes as these individuals are at higher risk for the disease. As with diabetes, many of the risk factors for atherosclerosis can be controlled. Lifestyle changes that can be used to treat and possibly prevent atherosclerosis include:

  • Glucose control. Research has shown that strict glycemic management in people with type 1 diabetes reduces the development of atherosclerosis. The American Diabetes Association has reported that intensive glucose control can yield benefits years after the control is implemented.  The research suggests that glucose control should begin as early as possible because the greatest amount of damage occurs in the first few years of the disease. Individuals with diabetes should follow their diabetes management plan as designed by their healthcare professionals.
  • Healthy diet. A diet low in saturated fats and trans fats and high in fiber can help control weight, blood pressure and cholesterol. Excess blood fats (lipids) and cholesterol contribute to atherosclerosis and other medical complications. An unhealthy diet can lead to obesity,which is closely linked to diabetes and atherosclerosis.
  • Exercise. Regular physical exercise can improve circulation and condition muscles to use oxygen more efficiently. Physical activity can also develop new blood vessels that form a natural bypass around obstructions, allowing more blood to reach the arms and legs. Research on obese individuals indicated that people who lost just 7 percent of their body weight and did moderate physical exercise improved their blood vessel function by 80 percent.  Thirty minutes or more of exercise each day can reduce the risk of atherosclerosis as well as complications associated with diabetes.
  • Weight control. If an individual is overweight or obese, the chances of developing atherosclerosis and cardiovascular problems increase significantly. Maintaining a healthy weight and body mass index (BMI) is important for control of diabetes and atherosclerosis.
  • Not smoking. Nicotine has been shown to narrow the arteries and restrict the blood vessels. In addition, tobacco use has been linked to high cholesterol and damage to the artery walls. One of the best ways to improve cardiovascular health as well as glucose control in diabetes is to quit smoking.
  • Stress management. Stress can contribute to atherosclerotic risk factors such as overeating and high blood pressure.

Although lifestyle changes can improve the health of the arteries, certain types of medications can help slow or reverse the effects of atherosclerosis. Types of medications that physicians may prescribe include:

  • Antiplatelets. These drugs, such as aspirin, reduce the likelihood that blood factors called platelets will clump together on the walls of an artery.  In the case of atherosclerosis, antiplatelets prevent the formation of blood clots that can cause further blockage.
  • Cholesterol-reducing drugs. These medications can improve a patient’s cholesterol profile, which may help slow, stop or reverse the buildup of plaque on the artery walls.
  • Anticoagulants. In certain instances, a physician may prescribe these drugs to help prevent clots from forming in the arteries and blocking the blood flow to the tissues.
  • Antihypertensives. Vasodilators such as ACE inhibitors, angiotensin-II receptor blockers and calcium channel blockers prevent the muscles in the walls of the arteries from tightening, which narrow the arteries.
  • Other medications. In some cases, the physician may prescribe medications for other complications, such as nitrates to relieve angina or folic acid for high levels of homocysteine. If glucose control is a problem in diabetes patients, medications may be changed to improve the condition. Recent research suggests that antidiabetic agents such as thiazolidinediones might help fight atherosclerosis.

It is important for the physician to consider any interactions between these drugs and insulin medications. Individuals with diabetes should inform the physician of the exact type and strength of insulin they are taking, as well as their schedule.

If a physician notes severe symptoms, a serious blockage may be present. This blockage can cause damage to tissue or organs and may require surgical intervention. Surgeries that may be used to correct the condition include:

  • Angioplasty. A thin balloon–tipped catheter is inserted into the blocked or narrowed part of the artery. The balloon is inflated, pressing the plaques against the artery walls. This procedure opens the artery to allow increased blood flow. A mesh tube (stent)may be left in the artery to help keep it open.
  • Embolectomy. A catheter is inserted into the artery to remove a blood clot.
  • Endarterectomy. In this procedure, a surgeon makes an incision in the artery, removes the plaques and closes the artery.
  • Vascular surgery. This bypass operation takes a graft from another part of the body or from a synthetic tube and places it in a blocked or narrowed artery. This graft allows the blood to flow around the blocked or narrowed artery and is often used in the legs. It also can be used to repair a large or leaking aneurysm in the aorta.
  • Thrombolytic therapy.  A physician may insert a clot-dissolving drug (“clot buster”) into a blood clot to break up the blockage.

If the atherosclerosis is present in the arteries of the heart, a coronary artery bypass surgery may be recommended by the physician. If the disease affects the arteries of the neck, the physician may recommend carotid artery surgery to remove the plaque buildup. These arteries supply the brain, and it is crucial to keep them as free from plaques as possible to avoid a stroke.

Because individuals with diabetes have an increased risk of atherosclerosis, it is important that they be closely monitored for any symptoms. If detected early, treatment can be successful in slowing or possibly reversing the effects of the disease. If atherosclerosis goes undetected, however, the result can be an emergency situation, such as a heart attack or stroke.

Questions for your doctor

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about atherosclerosis:

  1. How much does my diabetes or prediabetes increase my odds of developing atherosclerosis?
  2. Could my leg pain be due to atherosclerosis? What other signs of atherosclerosis should I watch for?
  3. What tests for atherosclerosis might I need to undergo, and what do they involve?
  4. What do my test results show? Do I have or am I at risk of atherosclerosis?
  5. How does atherosclerosis differ from arteriosclerosis, peripheral arterial disease, cerebrovascular disease, carotid artery disease, coronary artery disease and diabetic angiopathy? Do I have any of these conditions as well?
  6. How and why does atherosclerosis affect type 1 diabetes and type 2 diabetes differently?
  7. How much does atherosclerosis increase my risk of heart attack, stroke and other cardiovascular conditions?
  8. Does my atherosclerosis increase my risk of foot problems, skin problems, kidney disorders, eye diseases or other conditions?
  9. Can I help treat or prevent atherosclerosis by making improvements in exercise, diet or other habits? How important is it that I quit smoking?
  10. Do I need medications to treat or prevent atherosclerosis? If so, which options do you recommend?
  11. Could my atherosclerosis require surgery? What would this involve?
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