Cardiovascular risk age: concepts and practicalities

Objectives

A young person with many risk factors may have the same level of risk as an older person with no risk factors. Thus a high-risk 40-year-old may have a risk age of 60 years or more. The aim of the study was to derive a generic equation for risk age, construct risk age charts, and explore the hypothesis that risk age is similar regardless of the cardiovascular disease (CVD) end point used.

Methods

The equation was generated by equating the generic formula for 10-year CVD risk (with unknown risk factor levels) to the generic formula for 10-year CVD risk in a person with age = x and ideal risk factor levels (total cholesterol 4 mmol/l, systolic blood pressure 120 mm Hg, and non-smoker) and solving for x. To examine the consistency between risk ages for different end points, a risk age based on risk of CVD fatal events and based on risk of fatal and non-fatal CVD events was derived for each of the participants in the FINRISK population study. The correlation between these risk ages was examined.

Results

A generic equation for risk age was derived. The generic equation could not be used for SCORE (Systematic COronary Risk Evaluation), because the age is included in the baseline. Therefore a table of SCORE risk ages was developed by looking up the risk age corresponding to each combination of risk factors in the chart. Risk age remains similar regardless of the cardiovascular end point used, which bypasses the dilemma of whether to use a risk-estimation system based on CVD mortality or on the more attractive but less reliable end point of total CVD events. On the basis of the equation, risk age is not dependent on baseline survival and therefore recalibration is not required.

Conclusions

Risk age is an intuitive and easily understood method for communicating about risk, particularly in younger patients, and may facilitate lifestyle change in younger patients. However, treatment decisions should be based on absolute risk, as recommended by guidelines on CVD prevention.