Stroke: Reducing Risk-Part III

Many vascular specialists say that two diagnostic tests are available but underused in helping to prevent strokes from occurring. These two tests are the carotid ultrasound test and the ankle-brachial test. Vascular doctors will begin a campaign to have Medicare cover the cost of these two tests beginning at the age of 65.

The cost of each of these tests can vary from about $45 to several hundreds of dollars depending on where the test is taken. There is a private company called Life Line Screening that offers these two tests, plus ultrasound tests for aortic aneurysms and an exam for osteoporosis for $129. Hospitals that do the carotid artery test charge about $250 for this test.

The American Vascular Association offers free screenings from time to time. There will be one at the Grand Hyatt Hotel in New York City on October 1. For a list of other sites where these screenings will take place go to The Society of Interventional Radiology will also offer free screening at various sites during the year. To obtain a list of where these screenings will be held go to

Those who are at high risk of incurring strokes include those who have a family history of stroke, those who have diabetes or those who have high blood-lipid levels. There is evidence that, once carotid artery blockage is found, either drugs or surgery can treat it. A blockage of the carotid artery that exceeds 80% is considered sufficient a level to warrant surgery. The carotid artery is near the neck's surface, so an ultrasound test done by a professional sonographer can detect the problem.

There is a turf war going on among medical professionals in this area. There are 2,400 vascular surgeons and physicians in this country and there are 22,000 cardiologists in the U.S. The American Stroke Association, which is made up of neurologists, says it is considering promoting these tests, but it isn't sure how cost effective the tests are.

The ankle-brachial test involves taking the blood pressure of the patient at the ankle and the brachial artery in the upper arm. The comparative ratios of the two should be about 1 to 1, and is known as the ABI ratio. A score of 0.9 means blood-flow blockage is significant enough to be considered abnormal

A group of specialists convened by the National Heart, Lung and Blood Institute issued new guidelines for what constitutes "normal" blood pressure. Under the new standards millions more Americans fall within the risk category, and thus expose themselves to suffering from the diseases associated with abnormal blood pressure. The guidelines established a new category called "prehypertension" to describe an additional estimated 45 million people with readings from 120 to 139 millimeters of mercury of systolic pressure or from 80 to 90 diastolic pressure.

Systolic pressure, which is the upper number, represents the pressure of arterial blood flow when the heart beats. Diastolic pressure, which is the lower number, indicates the pressure between beats. High blood pressure greatly increases the risk of heart attack, stroke, heart failure and kidney failure. The report also concluded that in people older than 50 "systolic blood pressure of more than 140 millimeters of mercury is a much more important cardiovascular disease risk factor than diastolic blood pressure."

Heaviness is the leading risk factor for developing high blood pressure, and weight loss nearly always brings down an elevated pressure. A government-tested diet has proven to be effective also in controlling hypertension. It is popularly called the DASH diet, which is the acronym for Dietary Approaches to Stop Hypertension. Reducing salt intake to a maximum of 2,400 milligrams a day can enhance the effectiveness of the diet.

As people age their blood pressure tends to rise. According to the Framingham Heart Study, 90% of those who have normal readings when they are 55 eventually develop high blood pressure. Blood pressure increases because most people's arteries narrow and stiffen with age. This study has been going on for more than decades.

According to a study being done at the Framingham Heart Study of the National Heart, Lung and Blood Institute nine out of 10 older Americans develop high blood pressure. The study further determined that more the two-thirds of the 65-year-olds developed high blood pressure within 10 years. The study has monitored residents of Framingham, Mass. since 1948.

Ramachandran Vasan an author of the study stated, "We know that high blood pressure is a preventable condition." He went on to say: " This would mean watching the diet you eat, watching the salt content, watching the fat content, exercising more regularly and getting your blood pressure checked periodically."

Readers should be aware that the mortality rate from stroke has declined considerably in the recent decade. In fact, the stroke rates in the United States are among the lowest in the world. This would appear related to the development of treatment modalities for hypertension, probably the leading factor for stroke. At the same time, mortality from stroke accounts for about one in 15 deaths in the United Statesómortality rate for men is 46.6/100,000 and for women is approximately 36.7/100,000. Note should be made that the rates are higher in the elderly and in African-Americans.

In a study paid for by Merck & Co., that was conducted on 9,193 men and women with hypertension in Scandinavia and the U.S. that compared Merck's Cozaar (generic version is named losartan) versus the beta- blocker drug known generically as atenol, Cozaar was found to be vastly superior in preventing strokes and diabetes. Both Cozaar and atenol are leading blood pressure lowering medications. All of the participants in the study had shown early evidence of heart damage from high blood pressure (enlargement of their heart's left ventricle). Atenol is also sold under the brand name of Tenormin.

The study found that patients on Cozaar were 25 percent less likely to suffer strokes and 25 percent less likely to develop diabetes. Dr. Bjorn Dahlof of Goteburg University in Sweden presented the results of the study at the American College of Cardiology meeting in Atlanta.

Researchers are always on the look out for ways to protect the individual from risk of stroke. The difficulty of these studies is that trying to isolate a single nutrient that may be effective is a difficult task. Many nutrients interact with each other at different levels of their metabolism, thus having positive and negative synergistic effects on a wide range of nutrients in the body, thus they may not be shown to have a causal relationship per se.

However, there appears to be a plethora of studies that indicate that consumption of a diet rich in potassium, magnesium and fiber is protective against stroke mortality in man. The protective effects were seen particularly in hypertensive subjects, but were observed at all levels of blood pressure and remained significant after adjustment for blood pressure level.

A high intake of fiber and potassium is the result of a diet rich in fruit and vegetables, associated with intake of many other nutrients, such as vitamins, which may also affect stroke risk. This complicates cause and effect implications.

It should be noted that in most studies of the role of nutrients in risk prevention, the individuals who most benefit from the nutrient intake are those who do not smoke, usually have a high level of physical activity, consume low levels of alcohol, have less fat and take more micronutrients than the other individuals in the study. All this points out that health is related to healthy living standards involving nutritious food intake, moderate physical activity and a psychological healthy outlook on life which minimizes but does not eliminate stress effects.

In general, most individuals do not implement dietary strategies to control disease risk while they are healthy. In cardiovascular medicine, it is believed that it is never too late but also never too early to try to prevent disease.

While one needs to focus on the classical causal stroke risk factors (see Stroke I & II), including high blood pressure, smoking, artherial thrombosis, and diabetes mellitus, the additional implementation of a higher intake of protective nutrients might result in a higher risk reduction.

Poorly controlled diabetes mellitus can lead to increased blood pressure; increased intake of dietary fiber may improve glucose tolerance and the clinical manifestation of diabetes and lead also to reduced blood pressure.

Potassium can effect blood pressure by affecting a variety of factors and functions in the body, including natriuresis, barorecepter sensitivity, vasodilation, catecholaminergic functioning, the central nervous system, glucose tolerance and renin-angiotensin-aldosterone system. Accordingly, potassium may decrease stroke risk via its effect on blood pressure. A diet high in potassium has been found to be cardio-protective by other possible mechanisms as well. Higher concentrations of potassium may inhibit the formation of free radicals (a molecule with an unpaired, highly reactive electron; the oxygen-free radical is a byproduct of normal metabolism, produced as cells turn food and oxygen into energy, and has been implicated in processes within the body that result in aging as well as cancer, atherosclerosis, cataracts and neurodegeneration.) at the level of the endothelial cells, thus affecting vasomotion. Furthermore, potassium has been shown to inhibit the proliferation of smooth muscle cells and inhibit platelet aggregation and formation of artherial thrombosis. Potassium concentrations may also represent an important modulation of the death of cerebellar neurons in different in vitro models.

A diet rich in fruits and vegetables generally has a low calorie density and is accordingly associated with lower risk of weight gain and may even lead to weight loss. Overweight and obesity, especially abdominal obesity, is associated with increased risk of cardiovascular disease, including high blood pressure. Several studies reported that fat accumulation in the abdominal area might be an independent risk factor for stroke.

A recent study reported that the prevalence of silent cerebral infarction (SCI) or lesions in the general population aged 50-70 years is about 11%. The major risk factors for SCI's are smoking and hypertension. These SCIís showed upon brain imaging in the absence of clinical symptoms. Such data underlines the importance of preventative strategies, especially dietary changes, in all people, independent of age, sex and risk factors.

  1. Sacco RL. Risk factors and outcome for ischemic stroke. Neurology 1995; 45 (Suppl 1): S10-14.
  2. Ascherio A., Rimm EB, Hernan MA, et al. Intake of potassium, magnesium, calcium and fiber and the risk of stroke among US men. Circulation 1998; 98:1198-1204
  3. Spiller CA. Dietary fiber in human nutrition. Boca Raton, FL
  4. Kannel WB, Cupples LA, Ramaswami R et al. Regional obesity and risk of cardiovascular disease: The Framingham Study. J Clinical Epidemiology 1991; 44:183-190.
  5. Suter PM The effects of potassium, magnesium, calcium and fibers on risk of stroke: Brief critical review. Nutritional Reviews 1999; 57(3): 84-91


Written by Harold Rubin, MS, ABD, CRC, Guest Lecturer
updated September 29, 2004

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Stroke I-General Information
Stroke II-Stroke Treatment
Stroke Part IV-Role of aspirin & heparin in ischemic stroke

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