Copyright © 1995 by Steven J. Milloy. All rights reserved. First edition. Published by the Cato Institute, 1000 Massachusetts Avenue, N.W., Washington, D.C. 20002. Library of Congress Catalog Number: 95-72177. International Standard Book Number: 0-9647463-2-8.
Chapter 8
The Big Risk Number
You've calculated your relative risk and you've made it statistically significant. Is that enough? Can you just write up your results, get them published and start filling out those federal grant applications?
You can, but you haven't yet maximized your chances for success. There's one last thing to do and it's easy as pie. You simply take the innocuous relative risk number and "morph" it into a public health crisis.
You need to calculate a risk estimate for some population, preferably a large population or, better yet, all 250 million Americans. If you can figure the number of cancer cases or premature deaths associated with your risk, you're sure to get instant national attention. But how do you do this? Simple. Tell your statisticians you want to calculate an attributable risk. They know how.
Attributable risk is intended to indicate what percentage of deaths in a population are caused by a risk. For example, saying that "16 percent of all deaths are due to being overweight" is an attributable risk. You've attributed 16 percent of all deaths to obesity. All you need to do then is figure out how many deaths there are annually (about 2.2 million in the U.S., according to 1991 statistics), then multiply the number of annual deaths by the attributable risk (16 percent). Voila! A public health crisis is born!
EXAMPLES OF ATTRIBUTABLE RISKS
Risk
Annual Deaths Attributed to Risk
Obesity
350,000 from all causes (Source: derived from 1995 Harvard University Study)
Smoking
390,000 from all causes (Source: U.S. Surgeon General)
Radon
40,000 from lung cancer (Source: U.S. EPA)
Chlorinated tap water
10,000 from bladder & rectal cancer (Source: Morris et al 1992)
Environmental tobacco smoke
3,000 from lung cancer (Source: U.S. EPA)
Now your statisticians (if they are competent and conscientious) should ask if you really want to calculate an attributable risk. This query will be based on the following warning that appears on the package of every statistical analysis program:
STATISTICIAN'S WARNING: ATTRIBUTABLE RISK MAY NOT BE SCIENTIFICALLY JUSTIFIABLE. IT IS CALCULATED FROM VERY UNCERTAIN STATISTICAL ASSOCIATIONS. THESE ASSOCIATIONS MAY NOT REFLECT TRUE BIOLOGICAL CAUSE-AND-EFFECT. AT BEST, A STATISTICAL ASSOCIATION IS A REPRESENTATION OF WHAT WAS OBSERVED IN A PARTICULAR POPULATION STUDIED AND IS NOT APPLICABLE TO OTHER POPULATIONS NOT STUDIED.
You, of course, should ignore this warning.
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