Understanding the relationship between relative and absolute risk

✍ Scribed by William D. Dupont; Walton D. Plummer Jr.,

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 756 KB
• Volume: 77
• Category: Article
• ISSN: 0008-543X
• DOI: 10.1002/(sici)1097-0142(19960601)77:11<2193::aid-cncr2>3.0.co;2-r

✦ Synopsis

BACKGROUND.

Relative risks are the most common statistics used to quantify the risk of mortal or morbid outcomes associated with different patient groups and therapeutic interventions. However, absolute risks are of greater value to b'oth patient and physician in making clinical decisions.

METHODS.

The relationship between relative and absolute risks is explained using graphical aids. A program to estimate absolute risks from relative risks is available on the Internet (see ftp:llfp. uanderbilt.edulpublbiostat1absrisk. txt). This progiram uses a competing hazards model of morbidity and mortality to derive these estimates.

RESULTS.

When a patient's absolute risk is low, it can be approximated by multiplying her relative risk by the absolute risk in the reference population. This appl-oximation fails for higher absolute risks. The relationship between relative and absolute risk can vary dramatically for different diseases. This is illustrated by breast cancer morbidity and cardiovascular mortality in American women. The accui-acy of absolute risk estimates will be affected by the accuracy of relative risk estimates, by the appropriateness of the reference groups used to calculate relative risks, by the stability of cross-sectional, age-specific morbidity and mortality rates over time, by the influence of individual risk factors on multiple causes of mortality, and by the extent to which relative risks may vary over time.

CONCLUSIONS.

Valid absolute risk estimates are valuable when making treatment decisions. They can often be obtained over time intervals of 10 to 20 years when the corresponding relative risk estimates have been accurately determined.