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Diabetes and Heart Disease — An Intimate Connection

By By Om P. Ganda, M.D., Director, Lipid Clinic, Joslin Diabetes Center

A strong link between diabetes and heart disease is now well established. Studies from Joslin Diabetes Center several years ago showed a two- to threefold increase in the incidence of heart disease in patients with diabetes compared with those without diabetes who were being followed in the Framingham Heart Study. Women with diabetes have an even greater risk of heart disease compared with those of similar age who do not have diabetes. In fact, cardiovascular disease leading to heart attack or stroke is by far the leading cause of death in both men and women with diabetes. Another major component of cardiovascular disease is poor circulation in the legs, which contributes to a greatly increased risk of foot ulcers and amputations.

Several advances in the treatment of heart disease over the past two decades have improved the chances of surviving a heart attack or stroke. However, as the incidence of diabetes steadily increases, so has the number of new cases of heart disease and cardiovascular complications. Unfortunately, in patients with diabetes, improvement in survival has been less than half as much as in the general population.

Why Is Heart Disease So Common in People With Diabetes?

Diabetes by itself is now regarded as the strongest risk factor for heart disease; however, a variety of mechanisms—not solely blood glucose levels—most likely come into play. The blood vessels in patients with diabetes are more susceptible to other well-established risk factors, such as smoking, high cholesterol and high blood pressure, and more than 90% of patients with diabetes have one or more of these additional risk factors.

Some of the increased susceptibility to blood vessel damage that people with diabetes have could be due to the long-term effects of inadequate control of blood glucose levels on the tissues or as a result of other cell damage related to diabetes. There is also evidence that being overweight, having a sedentary lifestyle and poor blood glucose control contribute to the increased chance of high blood pressure and abnormalities in blood lipids (i.e., high cholesterol, high triglycerides and a low level of HDL cholesterol—the “good” cholesterol.

Research on the role of additional risk factors is being conducted. Evidence shows that patients with diabetes have an increased level of low-grade inflammation of their arterial lining, a process that initiates the blood vessel changes leading to heart disease. Some of the new tests to assess this inflammation are being evaluated, including C-reactive protein and homocysteine.

How to Prevent or Delay Heart Disease

The best way to prevent or delay the development of cardiovascular disease is to prevent diabetes itself. People with increased risk for diabetes can be identified. A large National Institutes of Health-sponsored study, the Diabetes Prevention Program, and other studies have proven that modest weight reduction and a 30-minute exercise routine five days a week can reduce the development of type 2 diabetes over three years by more than 50%. Moreover, even people at risk for diabetes or those with prediabetes, in addition to those with diabetes, frequently have abnormalities in blood pressure and lipid levels that can be detected and treated to prevent cardiovascular disease.

Weight control and smoking cessation are two important lifestyle measures that have an impact on preventing heart disease. Studies show that even in overweight people, regular physical activity has major cardiovascular benefits.

In the last 10 years, large-scale research studies around the world have shown that optimal control of LDL cholesterol (the “bad” cholesterol) and blood pressure can prevent adverse cardiovascular outcomes by 30% to 50%. The American Diabetes Association and the American Heart Association recommend an LDL cholesterol goal in all adults with diabetes at less than 100 mg/dl. In people who already have heart disease, a more desirable LDL cholesterol goal should be less than 70 mg/dl, based on evidence from more recent studies. The blood pressure goal in all patients with diabetes is less than 130/80. In most patients with diabetes, reaching these targets for blood pressure could require two or more medications. Fortunately, we have safe and effective medications available to help patients meet their lipid and blood pressure goals.

In addition, good control of blood glucose levels and low-dose aspirin can add to these benefits. For A1C tests—a measure of average blood glucose levels over the preceding two to three months—the goal is less than 7%..

Take Action

To sum up:  there's no totally certain way to avoid heart disease and circulation problems. But there are lots of things to do to cut your risk.

Stop Smoking

This is the single most important thing you can do! Nicotine narrows and restricts blood vessels. So does having diabetes. You can't change having diabetes. But you can stop damage caused by nicotine. Join a stop smoking group. Get support. Plan to quit. Cut back. And then, stop!

Lose Weight If Overweight

Being overweight tends to increase your blood glucose, blood pressure and blood fat levels. Even a modest 10-20 pound weight loss will improve your levels. To lose weight, skip crash weight loss programs. Emphasize eating healthy foods that are low-fat and high-fiber and increase your physical activity. These will help keep your blood glucose and blood fat levels in a healthy range. Check with your healthcare provider to determine how to safely increase your physical activity.

Keep Blood Pressure in Control

High blood pressure increases the risk of stroke. Have your blood pressure tested at least twice a year. If your blood pressure is over 130/80, lose weight. This is a lower target than for people who don't have diabetes. Follow a low-salt meal plan. Increase your physical activity. And ask your healthcare provider about medications to lower blood pressure.

Get More Physical Activity

Physical Activity keeps your heart healthy, and helps keep blood glucose and blood fat levels in control. So don't be a couch potato. Talk with an exercise specialist to start a sensible physical activity program. Be sure to check with your healthcare provider before beginning or increaseing you physical activity program. Also be sure to ask if there are types of exercise you should not do because of other diabetes complications you have.

Define a set schedule for physical activity. Put it in your calendar. Stick to it. You'll be surprised how much better you feel!

Keep Your Blood Fats and Cholesterol in Control

High levels of blood fats, including cholesterol, increase the risk of heart disease. Because you have diabetes, you are more likely to have high blood fat levels. So pay special attention! Know your blood fat levels. There is now proof that lowering levels of so-called bad cholesterol (LDL cholesterol) in persons with diabetes greatly lowers the risk of a heart attack. Your target levels should be lower than those of someone without diabetes.

Your level of HDL (so-called good cholesterol) should be greater than 40 for men and  greater than 50 for women. Your level of LDL (so-called bad cholesterol) should be under 100. Your triglyceride level (another bad fat) should be under 150.

To reach these goals, follow a low-fat, high-fiber, lower calorie meal plan — weight loss decreases blood fat levels. See a dietitian for help. Get more physical activity, because physical activity lowers levels of bad fats and increases levels of good fats. Blood fat lowering medications may be needed if your cholesterol levels don't respond to these treatments.

Keep Blood Glucose in Check

Monitor your blood glucose regularly (according to how you were taught). Know how to take action based on your blood glucose checks. Know how to adjust your medication, exercise and meal plan if plasma blood glucose is unusually high (higher than 180 mg/dl two hours after eating or higher than 130 mg/dl before eating) or unusually low (lower than 70 mg/dl or below 90mg/dl with symptoms). High blood glucose increases the risk for all other complications of diabetes, so it’s important to know your blood glucose levels.

Know your target A1C. Hemoglobin A1C is a blood test your healthcare provider performs to tell how well your blood glucose has been controlled over the past two months or so. Your A1C should be lower than 7%. If it is running higher than 7% and nearer to 8.0%, or even higher, ask your diabetes treatment team for help with your treatment plan.

Page last updated: September 15, 2019