Update From the Medical Journals: January 2012 - What Your Doctor Is Reading - Harvard Commentaries

What's the latest news in the medical journals this month? Find out what your doctor is reading.

Women with Healthy Bones Can Repeat Bone Density Test in 15 Years
Study Ponders Statin Drug and Diabetes Link
More News in Brief: CT-Scan Dye Can Affect Thyroid; Sex Called Safe for Most Heart Patients; Safety of New Blood Thinner Gets a Closer Look

Osteoporosis is the name for bones are "thin" (fragile). It can lead to hip fractures and spine fractures in elderly people. Bone-building drugs can help treat osteoporosis.

Doctors diagnose osteoporosis with a bone mineral density (BMD) test. This is an X-ray test that takes about 10 minutes and costs roughly $250. Guidelines recommend that all women age 65 and older and men age 75 get the test. Women who have any special risks for osteoporosis (for example, if osteoporosis runs in the family) can get screened at a younger age, usually any time after menopause.

But doctors had no guideline for how often to repeat this test. Many have been repeating the test every two years for most women based on their own judgment. Findings of a study published January 19 in the New England Journal of Medicine will give doctors some testing intervals to follow.

A bone density test gives you a T-score. A normal T-score is between zero and -1.0. Your T-score can tell you if you have osteoporosis (T-score of -2.5 or lower), or milder bone thinning called osteopenia (T-score between -1.0 and -2.5).

Researchers looked at the health records of almost 5,000 women over 15 years. The women had never had a fracture, and all of the women were older than 65. The study was limited to women who did not have osteoporosis on their first bone density test.

Fewer than 1% of women with a normal bone density result developed osteoporosis over the 15 years. For women with mild osteopenia, 5% developed osteoporosis in that time. But 67% of women with severe osteopenia went on to have osteoporosis on subsequent tests. Based on these results, the researchers recommend this schedule of repeat testing.

Women with osteoporosis (T-score -2.5 or lower) were not part of this study. Doctors usually repeat bone density tests for women who have osteoporosis only if repeating the test will be used to adjust their treatment plan.

Doctors are likely to adopt these screening intervals, since they are the first ones recommended that have been based on evidence. Men were not included in this study.

About 1 out of 4 U.S. adults over age 45 takes a statin drug. Statins are the most popular drugs to lower cholesterol. They include atorvastatin (Lipitor), simastatin (Zocor) and others. Recent research has sparked a debate among experts about whether or not taking statins increases the risk for diabetes. On January 10, the journal Archives of Internal Medicine published a study that added to this discussion.

Researchers used information from a huge study of 153,840 women ages 50 to 79 that began in 1993. The study was an observational study. The researchers did not randomly assign one group of people to take statins and another group to take a placebo pill. Instead, in this more simple study, they followed the women over time and noted how many women who took statins also developed diabetes.

They found that statin users were more likely to develop diabetes. About 10% of women who took statins developed diabetes. Only 6.4% of those who did not use statins developed the disease. Other studies have suggested a similar trend for both men and women. Those studies haven't been as large as this study, so they have not attracted as much attention in the news as this one has.

But doctors have been quick to point out that the statins-diabetes link may not be a sign that statins cause this disease. People who need statins have bad cholesterol, and bad cholesterol goes hand in hand with the pattern of metabolism that also results in diabetes. It is likely that the connection is due to the underlying metabolism pattern, not a side effect of the drug. For people with high cholesterol, diabetes or heart disease, statins prevent heart attacks and strokes, and they save lives.

CT-Scan Dye Can Affect Thyroid. Contrast dye is frequently given through an intravenous (IV) line during computed tomography (CT) scans and cardiac catheter procedures. This dye frequently contains iodine. Doctors are careful to watch for allergic reactions and kidney stress after exposure to this dye. But a study in the January 23 issue of the Archives of Internal Medicine shows this dye can also affect thyroid function.

Researchers did this study because the thyroid gland uses iodine to make thyroid hormone. Exposure to large doses of iodine can sometimes permanently change thyroid function. However, doctors were not aware that a small exposure to iodine, such as a dose of intravenous dye, could also affect the thyroid. The study included patients who had normal thyroid function before receiving the contrast dye. They were compared to a group of patients who never received dye. The researchers discovered that patients were more likely to develop hyperthyroid (overactive thyroid) disease or hypothyroidism (underactive thyroid) if they had been exposed to the dye.

Based on the numbers in this study, thyroid disease is probably not a frequent complication from contrast dye use. But this study should increase our caution about using iodine-based contrast dyes. Doctors might also consider checking thyroid tests after dye exposure. Dyes that do not contain iodine are available, and these are becoming more widely used (mostly due to allergy concerns.)

Sex Called Safe for Most Heart Patients. The American Heart Association issued a scientific statement saying that it's safe for most people with heart disease to have sex. This statement appeared in the journal Circulation on January 19. People who should check with their doctors first include those who have chest pain (angina) during exercise or during sex, people who have had a heart attack within the last two weeks, and people who have advanced heart failure or valve disease.

Blood pressure and heart rate both go up during sex. The "cardio" workout that comes with sex can vary. But when married couples are wired to home monitors, sex is roughly the same as a moderately paced or brisk walk on a flat surface. In theory, it is possible for sex to trigger a heart attack. Sometimes rigorous exercise, anger or sex creates enough stress and strain to bring on a heart attack. But only a very small number of heart attacks start this way. And the increase in heart attack risk from sex is very small.

For a person with a high risk of having a heart attack in the next year (for example, a person with a history of one heart attack who rarely or never exercises) sex once a week would increase heart attack risk from about 10% per year to about 10.1% per year.

Safety of New Blood Thinner Gets a Closer Look. Warfarin (Coumadin) is a commonly used clot-prevention drug (also called a blood thinner.) A new family of drugs that can be used instead of warfarin has been well received. One of the new drugs is dabigatran (Pradaxa). But a new look at this drug's safety says people who take dabigatran may have a slightly higher risk of heart attack than people who are treated with older drugs like warfarin. The difference is small — less than 1%. People taking dabigatran also were more likely to have chest pain with little or no exertion. Research describing these new concerns was published in the Archives of Internal Medicine. This analysis combined data from seven prior studies.

It might not be fair to say that a heart attack is a side effect of dabigatran. Some experts think that these studies might just show that warfarin (and another drug looked at in the study, enoxaparin) are better at preventing heart attacks. The total number of heart attacks was pretty low. But it is a difference that might make the new drug a bit less of a new favorite.

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.