Attributable Risk

This classic slide was prepared by Geoffrey Rose from early Framingham cohort data showing a histogram of the distribution of people by arbitrary classes of increasing level of Total Serum Cholesterol (TSC).

Above the histogram columns is the actual number of coronary events counted for that TSC class in the early years of the study. It indicates that 70 percent of them occurred under the level of 280 TSC, and that most cases occurred among those people in the middle of the distribution rather than among those at the extreme.

Though the curvilinear rise in relative risk soars for people with ever-higher TSC, the most coronary attacks in the population that are attributable to TSC as a risk factor, occur in the mid- or “normal” TSC range for that population. Thus, to effectively reduce the burden of coronary disease in the population, a community strategy is required to lower the average level of TSC and shift the whole populations’ distribution downward. It should be complemented by the traditional medical strategy to identify and treat people with high TSC levels. (HB)