- Primary prevention uses a high-risk strategy, wherein individuals are screened and those over a threshold are treated often with medications.
- This strategy has the advantage of “tailoring” the intervention to each individual with the goal of optimizing benefits and risks. However, it involves high screening costs and the use of risk thresholds and risk prediction models to determine the global risk from multiple risk factors.
- For example, in the Framingham Heart Study, more than twice as many people developed CAD (coronary artery disease) with a cholesterol level <200 mg/dL, as did those with cholesterol levels >300 mg/dL. This is because less than 5% of the population has cholesterol levels higher than 300 mg/dl which would account for only 5% of the heart attacks even if everyone with this level had a heart attack. Only 20% of the US population with cholesterol <200 mg/dl develop a heart attack. Since they account for 60% of the US population, this would translate to at least 12% of the heart attacks, more than double that observed in those with very high cholesterol levels.
- Using risk factor thresholds fails to recognize that the relationship between most risk factors such as BP, LDL (low-density lipoprotein) cholesterol, smoking and CVD is continuous and linear. Therefore, intervening in only those with extreme elevations in risk factor levels misses the opportunity to avoid a large proportion of cardiovascular events that occur among people with “average” risk factor levels, which represent the majority of the population.
- Since the risk associated with most risk factors is a continuum, more people making small changes result in large benefit to the society, as opposed to large changes in a small number of high-risk patients. Although the benefit to the society is large, the benefit to individual member is small. This irony in preventive medicine is termed “Prevention Paradox”.1
- For more information see primordial prevention.
1. Rose G. The strategy of preventive medicine. New York: Oxford University Press; 1992.