Apr. 30, 2002 HONOLULU, April 25 – Women whose routine mammograms revealed calcification in the blood vessels of the breasts were at increased risk for stroke, although those who had calcification only in their milk ducts were not, according to a long-term study presented at the American Heart Association’s Asia Pacific Scientific Forum. “Women with breast blood vessel calcification had a 54 percent increased risk of ischemic stroke compared to women without calcification,” says Carlos Iribarren, M.D., Ph.D., M.P.H., investigator in the division of research at Kaiser Permanente in Oakland, California. Women who had calcification in their milk ducts, another finding during mammography, were not at increased risk of stroke.
The 16,305 women underwent routine mammography between 1964 and 1973 at Kaiser Permanente Hospitals as part of voluntary health checkups. Their health history was tracked for 20 years. “Mammograms, which are relatively inexpensive and recommended annually for women after age 40, eventually may be used for early detection of stroke risk among women. But it is too soon to recommend mammography for this purpose,” says Iribarren.
“Mammograms should not replace conventional cardiovascular risk assessment tools, such as cholesterol measurements, blood pressure, smoking status, physical activity, diet or newer blood markers, such as homocysteine levels or C-reactive protein,” he says. However, mammograms might someday be used in addition to standard screening tools to better determine a woman’s risk, he added.
Homocysteine is an amino acid in the blood associated with a higher risk of coronary heart disease. C-reactive protein is a blood marker for inflammation, which researchers are finding may be an integral part of the cardiovascular disease process.
Ischemic stroke, the most common form of stroke, occurs when a blood clot blocks blood flow supplying part of the brain. Clots are more likely to block vessels narrowed by atherosclerosis, the build up of fats, cellular debris and calcium. Although attention has tended to focus on the fatty buildup, recent studies have begun to explore a possible relationship between the amount of calcification and the risk of cardiovascular diseases, such as heart attack and stroke.
Besides assessing stroke risk, the researchers also sought to determine whether certain factors make it more likely for a woman to accumulate calcium in the blood vessels and milk ducts of the breasts. They found that calcification of blood vessels inside the breast was more common among older women, those with a low educational background, those with diabetes and women who had three or more children.
Milk duct calcification, which was not associated with an increased risk of stroke, was more common among older women, cigarette smokers and among those who used hormone replacement therapy after menopause.
Researchers say calcification of breast blood vessels and milk ducts may occur by different processes. The breast blood vessels probably become calcified as part of the atherosclerotic process, whereas the milk ducts become calcified from other medical conditions.
“Women with diabetes were the most likely to have calcified blood vessels in their breasts, and also face a high risk of stroke, so these women should be monitored very closely for potential cardiovascular complications,” says Iribarren The researchers caution that since their study relied on mammograms done up to 30 years ago, additional studies using modern high-resolution mammography techniques are needed to confirm these findings.
Calcification as a marker for heart disease or stroke risk has recently been a topic of high interest for researchers. For example, in recent years, a new imaging technique, Electron Beam Computed Tomography (EBCT), has made it possible to measure the amount of calcium in arteries. Studies have shown a correlation between the degree of calcification and the risk of heart attack or stroke. However, grading the degree of risk associated with a particular degree of calcification is still an area of active study. “Cardiovascular diseases, such as heart attack and stroke, continue to be the leading cause of death among women in the United States. However, despite recent advances in understanding the risks of cardiovascular diseases, currently identified risk factors fail to predict up to half of future cardiovascular events,” says Iribarren. “Mammography may one day be a valuable addition to traditional screening methods.”
Co-authors include: Claiborne Johnson, M.D., University of California, San Francisco; Alan S. Go, M.D. Kaiser Permanente Division of Research, Oakland, Calif.; Stephen Sidney, M.D., Kaiser Permanente Division of Research, Oakland, Calif.; and David S Spring, M.D., Kaiser Permanente Oakland Medical Center, Oakland, Calif.
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