Heart Disease: Low-risk is not no-risk
Most physicians recognize that cholesterol testing is a flawed tool for prediction of heart disease. To improve on the weaknesses of cholesterol testing, the Framingham risk score is often offered as a better risk-assessment tool, a prediction system based on the 60 years of observations coming from the residents of Framingham, Massachusetts.
If we apply the Framingham risk scoring system to the U.S. population, several observations can be made:
- 35% of the adult population in the U.S., or 70 million, is deemed "low-risk." Low-risk is defined as the absence of standard risk factors for heart disease; low-risk persons have no more than a 1-in-20 chance (5%) of dying from heart disease in the next 10 years. Physicians are advised by the American Heart Association (AHA) and its experts that no specific effort at risk reduction is necessary.
- 25%, or approximately 50 million, U.S. adults are deemed "high-risk," based on the presence of 2 or more risk factors. High-risk persons experience 20-30% likelihood of heart attack in the next 10 years. People at high-risk are candidates for preventive efforts according to the guidelines set by the Adult Treatment Panel III (Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults; ATP III) for cholesterol-reducing statin drug treatment and for "lifestyle-modifying" advice.
- The remaining 40% of the adult population, or 80 million people, are judged "intermediate-risk," with likelihood of heart attack between 5-20% over the next 10 years. According to ATP III, this group should receive preventive advice and might be considered for statin drug treatment.
By the above scheme, the low-risk population will experience up to 3,500,000 heart attacks over the next decade, or 350,000 heart attacks per year.
The intermediate-risk population (without preventive treatment) will experience 8,000,000 heart attacks over the 10-year time period, or 800,000 per year (if we take the middle-ground of 10% likelihood of heart attack).
The high-risk population, the group most likely to receive standard advice on diet, exercise, and be prescribed statin cholesterol drugs, will have risk reduced by 35% by preventive efforts over the 10-year period. This means that heart attacks over 10 years will be reduced from 12,500,000 (once again, taking the middle-ground of 25% likelihood of heart attack) to 8,125,000 by standard prevention efforts, or 812,500 heart attacks per year.
This means that, following the standard approach, applying the widely-accepted Framingham risk scoring system and engaging in preventive practices as advocated by the AHA and ATP III will permit "only" two million heart attacks this year. (It also assumes that physicians will actually comply with standard advice, including going through the motions of performing the Framingham risk calculation. In reality, they often do not.)
These frightening predictions do, indeed, play out in real life. The numbers of heart attacks, death from heart attacks, and hospitalizations for unstable heart symptoms, as reported by the AHA (AHA 2008 Update; correspond to the numbers provided by these predictions.
These numbers are no secret. They are well known facts that have simply come to be accepted by the medical community. In other words, the standard approach to heart attack prediction makes the fact that two million people will succumb to cardiovascular events in the next year no mystery. This exercise in prediction is coldly accurate.
Heart attacks therefore occur in low-risk groups, intermediate-risk groups, and high-risk groups. While the percentages of people experiencing heart attacks differ in each risk group, they occur in substantial numbers - regardless of what level of risk you carry. Then how can you know your individual risk, even if you are "low-risk"?
My view: You cannot. The Framingham Risk scoring system is useful to examine risk within a population, but useless when applied to a specific individual. After all, if you are the "low-risk" person who has a heart attack, it's little consolation to know that your statistical likelihood was relatively low.
Risk therefore needs to be individualized, reduced to the risk experienced by a specific individual.
How do you do that? Easy. Measure the disease itself, i.e., coronary atherosclerosis, rather than statistical risk. The best way to do that today remains a simple heart scan, the test that uncovers and quantifies the amount of coronary atherosclerosis you have. This is as close as you and I can come to an index of disease that reveals individual risk. Carotid scanning is a second choice, an ultrasound test that uncovers atherosclerosis in the arteries of the neck