Update From the Medical Journals: October 2012
October 31, 2012
By Mary Pickett, M.D.
What's the latest news in the medical journals this month? Find out what your doctor is reading.
A four-year study has shown that some people who take beta blockers are not getting much benefit from long-term use.
Beta blockers include drugs like metoprolol (Toprol, Lopressor), atenolol (Tenormin), and carvedilol (Coreg). They limit some of the effects of adrenaline, your main stress hormone. (Adrenaline increases your heart's work by triggering "alpha" and "beta" receptors.) When you take a beta-blocker medicine, your heart beats slowly and steadily. And with less stress.
Doctors trust beta blockers. They:
These medicines are so important that some hospital review boards judge a hospital's quality by whether most or all of the heart attack patients are sent home with a prescription for a beta blocker.
But are we using beta blockers for too many patients, and for too long? Some doctors routinely recommend a beta blocker even for people who have coronary artery disease but no symptoms people with no angina and no heart attack. And some doctors even offer the medicines to people who have risk factors for heart disease, such as high cholesterol or diabetes, but do not have proven problems with their heart or arteries.
A new study of more than 20,000 adults taking beta blockers found no clear benefit on mortality (death) rates. The study lasted for almost 4 years. The study was published online by the Journal of the American Medical Association on October 2.
The study also looked at people who had suffered a heart attack years before. We know that beta blockers improve survival in the early months after a heart attack. Previous studies have made it look like there is a long-term benefit, too. But this large 4-year study one of the largest and longest studies that has looked at this question could not confirm a long-term benefit. It is possible that most of the benefit from beta blockers happens in the first year or two after a heart attack. Perhaps heart attack patients do not need to stay on a beta blocker for a lifetime.
Beta blockers do cause side effects. They can make the heart beat too slowly. They can cause fatigue, dizziness, nightmares or insomnia, impotence in men, depression symptoms in some people. They might worsen wheezing in people with lung disease. Elderly patients are particularly likely to have side effects.
For people with risk factors only (no true heart disease), taking a beta blocker does not seem to be worthwhile. And while doctors will definitely still recommend beta blockers to heart patients, this study might change how long we keep them on the medicine list. For people with heart failure, beta blockers are known to be helpful. For heart attack patients who do not have heart failure, more studies will need to be organized to tell us the ideal amount of time to keep taking a beta blocker.
Previous research has linked a lack of sleep to a higher risk for obesity and diabetes. A new, but small, study looked at the cells of people who don't get enough sleep. This study might explain why lack of sleep is linked to diabetes. The journal Annals of Internal Medicine published the study October 16.
Type 2 diabetes is caused by "insulin resistance," which is a change in the way cells react to insulin. Insulin is a hormone that controls the entry of blood sugar into cells. This process does not work efficiently when there is insulin resistance. If you have insulin resistance, the pancreas needs to make and release higher levels of insulin into the blood to overcome the resistance.
Seven healthy adults were assigned to sleep either 8.5 hours or 4.5 hours in a sleep lab for 4 nights in a row. After a 2-week break, the groups switched sleep times. After each 4-day cycle, researchers took samples of fat cells from the abdomen wall of the subjects. They also did blood tests to measure insulin. Insulin levels were nearly 3 times higher after people were sleep deprived. Also, cells that were sampled after the sleep-deprived period were 30% less able to respond to insulin when they were studied in a lab.
This study was too small for us to draw conclusions about the way too little sleep might relate to diabetes. But it does seem like a good reason for all of us to make sure we are getting enough sleep. This may be especially important for people who are overweight, or who have pre-diabetes or diabetes.
Mary Pickett, M.D. is an Associate professor at Oregon Health & Science University where she is a primary care doctor for adults. She supervises and educates residents in the field of Internal Medicine, for outpatient and hospital care. She is a Lecturer for Harvard Medical School and a Senior Medical Editor for Harvard Health Publications.