A study released the first week of February 2008 hit the media headlines hard. “Diabetes Study Partially Halted After Deaths” was the title of the version I read in the NY Times. The introductory paragraph was quite shocking: “For decades, researchers believed that if people with diabetes lowered their blood sugar to normal levels, they would no longer be at high risk of dying from heart disease. But a major federal study of more than 10,000 middle-aged and older people with type 2 diabetes has found that lowering blood sugar actually increased their risk of death, researchers reported Wednesday.” Does that mean we all have to rethink actually trying to control our blood sugars tightly? My answer is an emphatic “No!” and let me tell you why.
The over 10,000 study participants had an average age of 62, type 2 diabetes for about 10 years, higher than average blood sugar levels, and heart disease or other conditions like high blood pressure and high cholesterol that increased their risk of heart disease. They were randomly assigned to one of three types of treatments: (1) intense blood sugar control (a goal of an HbA1c less than 6%, which is a normal value for non-diabetic individuals); (2) intense cholesterol control; and (3) intense blood pressure control. In the first group, the participants did whatever it took to get their blood sugars lower, including taking multiple daily injections of insulin, taking two or more oral diabetes medications (as many as it took to reach 6%), and checking their blood sugars frequently, along with taking all of the medications they needed to treat other medical conditions, high blood pressure, and elevated cholesterol levels.
Among the study participants who were randomly assigned to get their blood sugar levels to normal levels, there were 54 more deaths–mostly from heart attacks–than in groups whose blood sugar levels were less rigidly controlled (257 deaths vs. 203 in the standard treatment group over four years). The patients were in the study for an average of four years when investigators called a halt to the intensive blood sugar lowering and put all of them on the less intense regimen.
Do these results mean that controlling your blood sugar is meaningless and dangerous instead of a goal of treatment? Surely not. Years’ worth of respectable research studies have shown that lowering your blood sugars can protect against kidney disease, blindness, amputations, and more, but as the article states, “the findings inject an element of uncertainty into what has been dogma — that the lower the blood sugar the better and that lowering blood sugar levels to normal saves lives.”
Why do I feel so strongly you shouldn’t overreact and change your position on intensive blood sugar control just yet? Certainly, it is important to stop and consider new research findings that go against the grain to see if they are valid and should direct therapies in new directions. As with all studies, there is also the possibility of varying interpretations of the set of results. A good instance of this was the hoopla over hormone replacement therapies (HRT) after the Women’s Health Initiative (WHI) was released. My co-author on an aging book, Dr. John Morley who is a geriatric specialist, believes that the results were misinterpreted and blown out of proportion, leading to major changes in therapies for older women. In the final analysis of the WHI results, the only significant finding in the end was that bone mineral density was improved slightly with hormone replacement, but none of the early findings of increased cancer risk remained significant in the end. His feeling is that many women going through early menopause for varying reasons are being deprived of a much-needed therapy as a result. (He also believes that women more than five years past menopause should probably not be on HRT, but younger women can benefit from it without significant health consequences.)
My point in bringing up the interpretation of the WHI is that this study claiming a raised risk of heart attacks with intensive diabetes control has much of the same feel to it. The media always go crazy over results from any study that go against the grain and sensationalize them. Although the article states that there were no differences among groups when the current study began, often when you go back and examine all of the data, that turns out not to be the case. Having not yet had the opportunity to read the actual study or review the data myself, I would hesitate to change any recommendations at this point.
On the contrary, there are overwhelming research data from previous studies supporting the benefits of lowering blood glucose levels for multiple reasons. For starters, people without diabetes do not suffer from solely diabetes-related complications, and their blood glucose levels are not elevated. People with pre-diabetes, however, have an increased cardiovascular risk for heart attack and stroke even without a diabetes diagnosis. Do we know anything about the diets that these study participants were on, their exercise patterns? Exercise itself naturally lowers oxidative stress leading to systemic inflammation, which is the most direct link to heart disease, insulin resistance, and diabetes complications. Dietary changes can also improve an individual’s oxidative status. Taking insulin should not necessarily cause less blood flow to the heart; in fact, it’s a vasodilator that increases blood flow to it. Thus, for me, the results of this study are far from conclusive and rather contradictory to what we know for certain.
As far as how rapidly you should lower your blood glucose levels, that is certainly a point to consider. I likely precipitated the onset of proliferative retinopathy in my own eyes by getting my blood sugars rapidly into a normal range once I got a blood glucose meter over 20 years ago. However, the eyes’ small blood vessels (microvasculature) and the heart’s much larger coronary vessels (macrovasculature) respond quite differently. When stimulated by exercise, the heart can actually form collateral circulation (new vessels) to enhance coronary blood flow. Moreover, it is usually safe for people with heart disease or prior heart attacks to exercise– doing so actually lowering their risk of having a heart attack (or another one).
It is always prudent to make dramatic lifestyle changes cautiously, but you can make many small changes that can have a larger impact on blood sugar control that would not necessarily have deleterious effects on your heart or cause heart attacks. Again, speaking as an exercise physiologist, I am well aware of the long-established studies showing that exercise improves blood flow to the heart even when coronary artery disease (blocked arteries) is present.
Having said all that, I still believe that the course to follow at this point is still the tried-and-true one; you should not let a single study alone completely disrupt what mounting evidence over years has shown. I can point out study after study that shows many health improvements with better blood glucose control and lower or normal HbA1c values. Many studies have proven that lowering the level of systemic inflammation is protective to your cardiovascular system and heart. However, I personally would never recommend lowering blood glucose levels with medications alone without incorporating physical activity and dietary changes as well, which is what may have been done in the halted arm of this study.
There’s a quote in the NY Times article that you need to consider closely: “It might be that patients suffered unintended consequences from taking so many drugs, which might interact in unexpected ways, said Dr. Steven E. Nissen, chairman of the department of cardiovascular medicine at the Cleveland Clinic.” It’s well documented that taking even just two medications can lead to untoward side effects from their interaction. The number of hospital admissions each year (and even deaths) as the result of medication interactions is actually astounding, but it’s not something that you often hear about. If anything, the results of this study just prove that it’s best to stick to the methods that we know help prevent and control diabetes complications and promote good health and longevity: regular physical activity, a health diet, good stress management, plenty of sleep, and judicious use of prescribed or other medications. Whatever you do, don’t give up on trying to keep your blood sugars as tightly controlled as you can just yet!