Risk factor criteria.

Abstract

The concept of the risk factor for chronic diseases, such as cardiovascular disorders, is derived from the application of epidemiological methods initially developed for infectious and nutritional deficiency diseases to chronic conditions to identify the factor(s) linked to the development of the chronic disease. Typically in infectious or nutritional deficiency conditions, a single causative agent or primary cause is identified. Thus, the cause of tuberculosis is the tubercle bacillus, and the cause of pellagra is niacin deficiency. However, for cardiovascular diseases, in which causes are usually complex and multifactorial, new concepts were required. For example, individuals with hypertension have a far greater risk for cardiovascular disease than those without hypertension, but many individuals with hypertension never have clinical sequelae, and many individuals with diagnosed cardiovascular diseases have no hypertension. One can also argue that many individuals who are exposed to the tubercle bacillus do not develop clinical tuberculosis, but the converse is not true; no one has tuberculosis without the tubercle bacillus. This provides a clear distinction between multifactorial diseases, such as coronary disease where the risk factor concept is paramount, and other health conditions. The initial application of the risk factor concept was well developed long before the term was coined. Early in the previous century, insurance companies noted that individuals with high blood pressure were at higher risk for premature mortality1 and therefore would be accepted for life insurance only on payment of an additional premium. Insurance companies also recognized the related risk factor of obesity, and imposed higher premiums on overweight clients. In this context, risk factors are used as predictors of disease and mortality. Surprisingly, insurance companies failed to recognize the enormous contribution of smoking to cardiovascular risk until later. Although the underlying concept had been widely discussed and applied, the term “risk factor” was …