Diabetes news: Are blood sugar levels not as important as we thought?

When a patient is first diagnosed with type 2 diabetes, one of the first things to discuss is getting and keeping their blood sugar at a normal level. Tight control of blood sugar has been shown to help prevent some of the damage diabetes can cause. However, a new study calls into question one long-held belief about blood sugar control: that it can help prevent fatal heart disease. The National Institutes of Health stopped one part of a study that was looking at what people with type 2 diabetes can do to reduce their risk of heart problems, which is a known consequence of diabetes. The study found that people who achieved very tight blood sugar control by taking medication did have fewer heart attacks. But they were more likely to be fatal.  I know that's worrisome, but keep reading, because there are things that you can do to help protect yourself.

Here's what my colleague, Dr. Howard Lewine, has to say about the study: 

This finding, although preliminary, is a big deal. But it doesn't mean that people with diabetes are at any less of a risk for heart attacks and strokes today than they were yesterday.

Two medical facts about diabetes and cardiovascular disease need to be reinforced.

• Type 1 diabetes and type 2 diabetes are very different diseases. With type 1 diabetes, very tight control of blood sugar starting at the time of diagnosis helps prevent further health problems. This includes cardiovascular disease.
• If you have either type 1 or type 2 diabetes, you will substantially lower your risk of heart disease and stroke by:

• Not using tobacco
• Exercising daily
• Eating a diet rich in vegetables and whole grains, and eating fish at least once or twice per week
• Maintaining a healthy weight
• Keeping your blood pressure in line, ideally less than 130/80
• Lowering your LDL cholesterol, ideally to 70 milligrams per deciliter

There are many benefits to avoiding high blood sugar. But high blood sugar is not one of the traditional, proven factors that increase the risk of heart disease. In fact, the new study results suggest that lowering blood sugar to normal by using medicine increases the risk of death.  

As it turns out, the results of another study of people with type 2 diabetes were published recently in the New England Journal of Medicine. Similar to the NIH study, it compared people who received intensive therapy to reduce heart disease risk to those who received standard therapy. The study, which lasted 13 years, was performed in Denmark.

The study was not designed to show which aspect of treatment made the most difference. But the authors suggested that two things had the greatest effect on reducing deaths: taking a statin to reduce cholesterol and lowering blood pressure with medicine. Taking aspirin also had benefit. Lowering blood sugar with insulin was not associated with less risk of death.

If you have type 2 diabetes and tend to have blood sugars in the high-normal range, you should bring them down. Doing this through diet, exercise, and weight loss will always improve your health.

The unanswered question is: What is the best drug to take if your blood sugar stays high despite your best efforts. Right now, the evidence suggests metformin as the first choice.

Metformin lowers blood sugar by decreasing the production of sugar in the liver. It also improves the action of circulating insulin. Metformin, used alone, almost never causes blood sugar to get too low. Also, unlike many other diabetes medicines, it does not cause weight gain. Some people actually lose a few pounds when taking metformin.

Not everyone should use metformin. People with kidney problems and congestive heart failure that require drug therapy probably should avoid metformin.

This report from the NIH questions one of the most widely held beliefs in medicine — the lower the blood sugar the better, as long as you don't get hypoglycemia. It is still true that people whose blood sugar naturally stays in the normal range are less likely to develop diabetes. And therefore, they are also less likely to develop the health problems related to diabetes. But once your blood sugars are above normal, it's not just lowering them to normal — no matter what it takes — that translates to better health.

Of course, before you make any decisions about a change in your diabetes care, talk with your doctor.

What do you think about this news about blood sugar control and heart health?

Julie K. Silver, M.D., is an assistant professor in the Department of Physical Medicine and Rehabilitation at Harvard Medical School. She is also the Chief Editor of Books for Harvard Health Publications.

Diabetes

Nearly 21 million Americans suffer from diabetes, and as anyone who has been affected by the disorder knows, it is about much more than a statistic: it means a new way of life. Diabetes: A plan for livingis a special report from Harvard Medical School that will help you learn how to better understand and manage your diabetes, including type 1 and type 2, as well as other variations of the disease. This report will show you that it's not just possible to live with diabetes; it's possible to live well.

 
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