Central  South  Dakota  Medical News
The Clinical View
  by P.E. Hoffsten, M.D.
29 October 2003

HEART DISEASE RISK FACTORS – DEBUNKING THE 50% MYTH

     One of my favorite hobbies is collecting and reading old medicine textbooks.  It is humbling to read the misconceptions in old medicine textbooks and think that perhaps 100 years from now, we will be viewed as equally misinformed.

     An interesting observation from 1890’s textbooks of medicine is that the concept of a heart attack is barely mentioned and yet today heart attack is the leading cause of death in our society.  Over the 100 years of the 20th century, lifestyle change has been substantial.  Now instead of infections being the leading cause of death as it was in the 1890’s, heart attacks are the leading cause of death.  Now we have electricity and computers and automobiles and modern machinery that decreases the physical labor required of human beings.  Our sedentary lifestyle has created an entire new set of diseases heart attack being the most prominent.

     In the early 1950’s, heart attack was recognized as a leading cause of death and studies were done to look for the causes of heart attack.  It was soon recognized that there were four major risk factors for heart disease.  These were:  1.  Hypertension causing approximately 33% of all heart attacks.  2.  Cigarette smoking responsible for 33% of all heart attacks.  3.  High blood cholesterol causing 20% of all heart attacks.  4.  Diabetes mellitus responsible for 10% of all heart attacks.  This leaves only 5% of all people who have heart attacks without one or more of these risk factors.  The more risk factors a person has, the more likely heart attacks are to occur.

     Recently, television, newspapers, and magazines have suggested that only 50% of all heart attacks are associated with these classical risk factors.  These sources tend to diminish the importance of the well known risk factors in causing heart attacks.  Alternatively, it has been suggested that C-reactive protein, lipoprotein (a), fibrinogen, and homocystine are important risk factors for heart disease.  There has been a tendency to discount the classical risk factors of blood pressure, cholesterol, diabetes and smoking saying that these are only responsible for 50% of all heart attacks. Thus was born the “50% myth”.  It is implied that the “real cause of heart attacks is still unknown.

     In a recent issue of the Journal of the American Association, there were four separate articles devoted to this topic.  Two large studies looking at the association of risk factors in heart disease in over 500,000 people were published.  Both studies showed that 90% of all heart attacks were associated with one of the four classical risk factors.  Where the 50% myth ever came from is not really known.  But when tested in over 500,000 people, the real answer is that the classical risk factors account for 90% of all heart attacks.  In a third article in the same issue of the Journal of American Medical Association and article was directed to the importance of the four new suggested risk factors mentioned above.  It was shown that CRP, lipoprotein (a), homocystiene and elevated fibrinogen have very little impact in the overall risk of heart attack accounting for less than 5% of all the heart attacks that occur.

     The specific recommendations at this point begin with blood pressure control.  In order to control blood pressure, you must know what your blood pressure is.  Check your blood pressure and be sure that it is 130/80 or less.  There is no such thing as normal high blood pressure.  If blood pressures are found in excess of 130/80, medications or life style changes are needed to get it down and prevent heart attacks.

     The second major risk factor is cigarette smoking.  Fortunately, the general public’s smoking habits have dropped from 65% of the adult population in the 1950’s down to 26% at this time.  Continued efforts are eradicating this most unhealthful problem are important.

     Cholesterol control is everywhere.  Getting a total cholesterol under 200 mg% and a bad cholesterol (LDL) under 100 mg% is recommended.

     Lastly avoiding diabetes with appropriate weight control and exercise is one of the most important steps a person can take.  If a person becomes diabetic, control of blood sugar, blood pressure and cholesterol takes on additional importance.  It would appear from these articles mentioned above, that the 50% myth is now de-bumped.  Working on the classical risk factors is re-enforced by these reports and well worth the effort.