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April 25, 2005
Risk Factors for Heart Disease Should Not Be Confused with Causes of Heart Disease
To get a handle on how your dietary fat, your blood cholesterol and your risk of heart disease may be related, it is important to recognize the difference between risk factors and causes. Risk factors do not necessarily cause disease. This is a crucial difference, one that has often tripped up researchers who study dietary fat and heart disease.
In some of the countries where heart attacks have been shown to be more common people eat more fat, but they also eat more protein and sugar, they smoke more cigarettes, and they buy more DVD players. Calories from fat tend to be more expensive than calories from other nutrients, so the intake of animal fat becomes statistically associated with deaths from heart disease in affluent countries. This information simply tells you that heart disease is more common in affluent countries, but it does not prove one thing causes the other.
The truth is that population studies never prove cause and effect. They are useful because population studies can flag important information that we can investigate further. Yet if you chose to ignore the need to prove cause beyond mere association, you could construct a graph that would show that heart attacks, strokes, hypertension, obesity and diabetes are all caused by television sets because there is a direct statistical correlation between the numbers of TV’s per household and the rate of these diseases!
When scientists collect and analyze data, they refer factors that tend to occur at the same time as the disease does as risk factors. This conventional naming is somewhat misleading because risk factors don’t necessarily convey risks but simply associations. As in the above example, owning multiple TV’s could be cited as a risk factor for heart attacks, even though owning a TV will not increase your risk of having a heart attack.
There are several hundred risk factors for heart disease, including smoking, high blood pressure, obesity, lack of exercise, stress, male sex, income, race, age, and baldness to name a few. To move beyond risk factors to determine the cause of cardiovascular disease, scientists must carefully design and conduct experiments to prove a direct cause-and-effect relationship. This research has been done, and it does not show a link between the amount of dietary fat and heart disease.
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Posted by james at April 25, 2005 6:37 AM