 | What Your Doctor Is Reading | | |
Update From the Medical Journals: May 2007
May 30, 2007  By Mary Pickett, M.D.
Harvard Medical School What's the latest news in the medical journals this month? Find out what your doctor is reading. Aspirin Lowers Colon Cancer Risk Aspirin probably offers some useful protection to people with a high risk of colon cancer, according to a study in the May 12 issue of The Lancet. Two earlier studies from the 1970s and 1980s — the British Doctors' Aspirin Trial and the UK-TIA Aspirin Trial — suggested that daily aspirin use could prevent colon polyps. A colon polyp can develop into a colon cancer after about 10 years, so preventing polyps is a good idea. But these initial aspirin studies lasted five years, which is too short a time to show how many cancers (if any) would truly be prevented. Also, complications from aspirin use, such as intestinal bleeding, made most doctors worry that the risks of aspirin might outweigh its benefits. British researchers continued to follow the nearly 7,500 adults (most of them over age 40) who participated in the initial randomized trials to see what effect aspirin had on preventing colon cancer. They found that people who took 300 milligrams or more of aspirin daily for at least five years did indeed have fewer colon cancers over the next 15 to 20 years. Compared with people who took a placebo pill during the original five-year study, people who took aspirin had 37% fewer colon cancers as a group. Even people with a family history of colon cancer in a close relative had a lower cancer rate. Since aspirin can cause ulcers and intestinal bleeding, experts are careful not to recommend its use for everyone. But people who have a high risk for colon cancer can be added to the growing list of people for whom daily aspirin might make sense. Back to top PET Scan May Detect Early Alzheimer's Disease The May 8 issue of Neurology published a small study suggesting that doctors may now have a test to diagnose Alzheimer's disease at a very early stage. The test that was used in the study is a "positron emission tomography," or PET scan. A PET scan is an imaging technique that uses radioactive particles to show the areas of the brain with the most metabolic and chemical activity. Recently, researchers found that a PET scan can detect the scarred areas that are known as amyloid plaques in the brains of people with advanced cases of Alzheimer's disease. Researchers wondered if the same pattern on a PET scan might be used to identify people with Alzheimer's disease at a much earlier stage. So, they asked 13 people who had been diagnosed with "mild cognitive impairment" to have a PET scan. People with mild cognitive impairment have some difficulty with short-term memory and information processing. The researchers compared these PET scans to PET scans from 14 people who were similar in age, but who didn't have mild cognitive impairment. The PET scans from the first group were very similar to people who had Alzheimer's disease, unlike those from the second group. This study is small, but it's important. It's possible that a PET scan might allow doctors to better predict whether progression to Alzheimer's disease will occur when patients complain of memory difficulty. A test to diagnose the disease at an early stage will be particularly useful if a treatment is developed that can halt progression of Alzheimer's. PET scans are not used at the present time to formally diagnose Alzheimer's disease because the results are preliminary. But we are very likely to see more of this technology in the near future. Back to top Diabetes Drug Is Surprisingly Linked to Higher Heart Attack Rate The New England Journal of Medicine published a surprising analysis on-line on May 22. Two doctors combined data from 42 separate studies to find out what impact rosiglitazone (Avandia) has on heart attack rates and heart-associated deaths. Rosiglitazone lowers blood glucose by making a person with diabetes more sensitive to insulin. However, when the combined data were analyzed, 43% more heart attacks were seen among people who were treated with this drug, compared with people who were treated with other diabetes medicines or with a placebo. This analysis may not be the final word on rosiglitazone, but it raises many concerns about the drug's safety. Since one of the major goals in diabetes treatment is to lower heart attack risk, most doctors will stop using rosiglitazone or switch to other treatments. Back to top More News in Brief - Osteoporosis Drugs May Trigger Irregular Heart Rhythm. A once-yearly injection of a new osteoporosis drug called zolendronic acid (Reclast) reduced the risk of spine, hip and other fractures among postmenopausal women according to a study in the May 3 Issue of the New England Journal of Medicine. But there was an unexpected risk associated with zolendronic acid. Women who received the medication had about one and a half times the usual risk for developing atrial fibrillation and some needed emergency treatment. Atrial fibrillation is an irregular heart rhythm that can sometimes cause dizziness, heart stress, or strokes. In the same journal issue, a lead researcher who tested the commonly-used osteoporosis drug alendronate (Fosamax) commented that the side effect appears to occur with that drug, too, although it occurs much more rarely. The safety of osteoporosis drugs will need to be closely reviewed, given this concern.
- Very Low Birth-Weight Babies Develop Health Problems as Adults. A study in the May 17 Issue of the New England Journal of Medicine finds that people who were born pre-term with very low birth weights are more likely to have both insulin resistance (the metabolic pattern that can progress to type 2 diabetes) and high blood pressure as adults. This tendency occurred whether or not the adults were overweight. Doctors might decide that people who have a history of very low birth weight should have special screening as adults to detect high blood pressure and diabetes.
- Genetic Testing May Predict Heart Disease Risk. A family history of heart disease in a parent or sibling is a known risk factor for heart attack. Scientists have just identified two genes that may be responsible according to two studies published online on May 3 by the journal Science. Between the two studies, researchers analyzed genes from more than 38,000 people. About one out of five people have a double (homozygous) copy of the first gene, which correlates with a risk for heart attack that is 1.6 times greater than the risk for non-carriers of the gene, and twice the risk for having a heart attack at an early age. One in four or five people have a homozygous copy of the second gene, which correlates with a 30% to 40% increased risk for heart attack. Genetic testing may help predict heart disease risk and help doctors individualize recommendations for heart disease prevention in the future.
Back to top Mary Pickett, M.D., is a lecturer for Harvard Medical School and an assistant professor of medicine at Oregon Health & Science University. At OHSU, she is a director of student programs and she oversees teaching of students and medical residents. She practices general internal medicine in Portland, Ore.
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