Excerpted from "When Risk Factors Unite," appearing in the Stroke Connection Magazine January/February 2005 (Science updated May 2008).
Common risk factors for coronary heart disease and stroke that can be controlled or treated include high LDL cholesterol levels, low HDL cholesterol levels, high blood pressure, smoking, diabetes, physical inactivity, and being overweight or obese.
High levels of LDL cholesterol contribute to the development of atherosclerosis as the cholesterol is deposited in artery walls, increasing the buildup of plaque. Low levels of HDL cholesterol raise stroke risk because HDL cholesterol carries cholesterol away from the arteries and back to the liver where it is removed from the body.
High blood pressure, 140/90 mm Hg or higher, causes the heart to work harder than normal. Both the heart and arteries are then more prone to injury. High blood pressure increases the risk of heart attacks, strokes, CHF, atherosclerosis and kidney failure. High blood pressure damages the inner lining of the blood vessels, which promotes the formation of atherosclerotic plaques. Over time the arteries become narrowed, hardened and less elastic, contributing even more to the high blood pressure. African Americans are more likely to suffer from hypertension; for instance, 80 percent of African Americans over 65 have high blood pressure. As a result, they have a greater rate of nonfatal stroke, fatal stroke, heart disease death and endstage kidney disease. High blood pressure also increases the risk of hemorrhagic stroke by weakening blood vessels. Also increasing hemorrhagic risk are arteriovenous malformations (AVM) and aneurysms, which are both vascular diseases that can be affected by high blood pressure. “AVM and aneurysm are congenital anomalies rather than diseases with risk factors we can treat,” says Dr. Roach.
For smokers, the risk of developing coronary heart disease is two to four times higher than for nonsmokers. Smoking is also a significant risk factor for stroke. Exposure to other people’s smoke increases the risk of heart disease and stroke, even for nonsmokers.The nicotine and carbon monoxide in cigarette smoke damage the cardiovascular system in many ways. Nicotine causes a short-term increase in blood pressure, heart rate and the flow of blood from the heart. It also causes the arteries to narrow. Carbon monoxide reduces the amount of oxygen the blood can carry. This, combined with the nicotine effects, creates an imbalance between the demand for oxygen by the cells and the amount of oxygen the blood can supply. Toxic products in cigarette smoke can damage the arterial wall, contributing to atherosclerosis. Smoking can make blood platelets stickier, which means clots are more likely to form.
Diabetes seriously increases your risk of developing cardiovascular disease. In fact, up to 75 percent of people with diabetes die of some form of heart or blood vessel disease, and their heart disease death rates are about two to four times higher than for adults without diabetes. Even when glucose levels are under control, diabetes increases your risk. If blood sugar is not well controlled, the risks are even greater. In addition, diabetes causes nerve damage that can make the pain of heart attacks harder to diagnose.
People who have excess body fat — especially if a lot of it is in the waist area — are more likely to develop heart disease and stroke even if they have no other risk factors. Excess weight increases the heart’s work. It also raises blood pressure and blood cholesterol and triglyceride levels, and lowers “good” cholesterol levels. It can also make diabetes more likely to develop.
“Scientists are beginning to understand that genetic influences go a long way in explaining why some families are more susceptible to strokes than others. Of course, genetic factors can influence the stroke risk itself, but genetics can also promote the other stroke risk factors,” added Dr. Roach.
The good news is that risk reduction for both CHD and stroke have a lot in common. Monitoring blood pressure and controlling it if it’s high, giving up smoking, eating a healthy diet, controlling diabetes, regular physical activity and maintaining a healthy weight all have a beneficial effect on risk of either condition.