The Illusion of Certainty: Health Benefits and Risks

Management of Environmental Quality

ISSN: 1477-7835

Article publication date: 8 August 2008


LLaurado, J.G. (2008), "The Illusion of Certainty: Health Benefits and Risks", Management of Environmental Quality, Vol. 19 No. 5.



Emerald Group Publishing Limited

Copyright © 2008, Emerald Group Publishing Limited

The Illusion of Certainty: Health Benefits and Risks

Article Type: Books and resources From: Management of Environmental Quality: An International Journal, Volume 19, Issue 5

Erik Rifkin and Edward Bouwer, with guest author Bob Sheff,Springer,Humana Press,Totowa, NJ, USA,December 2007,ISBN-13:978-0-387-48570-6,241 pp.

In its overall approach this book offers a way to explore quantitatively such vital questions as: “How solid is the link between high cholesterol and heart disease? Do regular screening tests for breast and prostate cancer lead to far fewer deaths from these diseases? How safe is the water we drink and the air we breathe?”

In an attempt to give meaningful answers to these questions two environmental scientists with many years of experience in analyzing health risks connected with air, water and soil pollution have written this book. They make it very clear at the beginning that they are not physicians: one (EJB) is a Professor of Environmental Engineering at Johns Hopkins University in Baltimore, Maryland and the other (ER) is an environmental consulting executive who provides assistance and guidance to federal and state regulatory agencies and corporations regarding the nature and magnitude of environmental risk and potential remediation strategies. Towards the end, a chapter endorsing the Rufkin and Bouwer’s findings is written by Bob Sheff, MD, a practitioner and administrator of large medical managed-care systems in the United States.

The first five chapters generically under the title “The Basics” deal with topics that, in the authors’ views, many people do not know how to ask and another group of people does not know the answer, such as: What is the probability that a breast lump is benign? What are the chances it is malignant? How does the cancer risk compare with the risks of tylectomy or mastectomy? Who does determine if a risk is acceptable?

The argument of the authors revolves about the following queries: “What is the risk in absolute terms? What is the risk in relative terms? What is the difference between the two?”. And how can the user of medical services or the inhabitant in an ecological threatened area evaluate the risks involved?

In order to answer some of those questions, the authors relied on the concepts of absolute risk vs. relative risk. The absolute risk is the risk of developing a disease over a specific period of time. Hence, the definition of absolute risk reduction (ARR) as the difference between the absolute risks in two groups, e.g. breast cancer death rates between two groups of women, those who had mamograms and those who did not. It appears that absolute risk and ARR values are seldom provided to the public. What we hear are relative values in the form of relative risk reduction (RRR) that employs the ratio of the two absolute risk numbers to measure how much the risk is reduced in a group as compared to another.

To exemplify the concept, suppose that 10,000 diabetics are administered a drug and 10,000 a placebo. At the end of a five-year study one drug treated individual has died whereas two died in the placebo group. The absolute risk reduction (ARR) is the difference between the death rates for the two groups. For the drug group the death rate was 0.01 percent (=1/10,000) and for the placebo group 0.02 percent (=2/10,000). By subtracting 0.01 from 0.02 the ARR result is 0.01 percent. Another way to look at the result is to state that for 10,000 diabetics in a theatre (vide infra), only one would benefit from receiving the drug over a five-year period.

By turning to relative risk, one compares the two in 2/10,000 with the 1 in 1/10,000. The reduction is from 2 to 1. Since this difference of 1 is 50 percent of the two deaths observed in the placebo group the relative risk reduction (RRR) is given as 50 percent. Thus, the same study with the same results can be expressed as 0.01 percent ARR or as 50 percent benefit as RRR. To the public it is more enjoyable to hear that the drug will halve one’s chance of dying rather than to hear that the drug would change the death rate by 0.01 percent, equivalent to say than one person out of 10,000 would benefit over a five-year period!

Although calculating RRR (the relative value) is a valid statistical method, it distorts the benefits to individuals when it is used to explain health risks, because the real benefit is usually considerably smaller than it appears. Since RRR is used by drug companies, the media, many physicians and others to illustrate health risks, it is important to understand how it differs from absolute risk. In this context it is remarked in the Foreword that “the book may be controversial” and it is likely to stimulate reflection and debate among scientists and policy-makers.

An interesting, appealing and original feature brought in by the authors is to present graphically a population group as a typical theatre with a seating capacity of, say 1,000 (picturesquely sectioned into stage, orchestra, front mezzanine and rear mezzanine). This is named the risk characterization theatre (RCT) and may illustrate the number of benefited individuals, the number of individuals contracting a disease, the merits of published risk factors, etc. It goes without saying that the RCT is consistently used to illustrate the specific case studies in this book which are: Vioxx™ and heart attacks; prostate cancer screening; statins, cholesterol and heart disease; colorectal cancer screening; health effects of smoking; chlorination of drinking waters and health risks; residential radon and risk of lung cancer; ecological risk assessment; Asian oysters in Chesapeake Bay; chromium and sediment toxicity.

These subjects are treated at different length and depth. An unbiased verdict based on the ARR and RCT is provided for each discussed study. Some definite results emerge: yes! there is a high risk of a cardiovascular event by taking Vioxx™, but no proof that prostate cancer screening reduces the risk of dying of this cancer, and so on. I found particularly good the chapter on drinking water and the chapter on chromium and sedimentation toxicity, where the authors spread their expertise. On the other hand, I found the chapter on whether to import Asian oysters recherché and prolix, the theme reflecting the proclivities and geographical location of the authors. The chapter by Sheff attempts to educate the actual or prospective patients regarding where to look at and what to ask from the physicians or health experts in order to reach an estimate of involved risk as accurate as possible. However, if this avenue were pursued ad nauseam it might cause a collapse of health delivery systems owing to its complexity.

An emotional note remains unsolved: in many of the assessments the risk involved in not following a certain treatment is very low, similar to the hypothetical example, namely that “one person out of 10,000 would benefit” from a treatment/procedure. That would suggest that it is not worthy to assume the expenses and side effect risks attached to it. However, imperceptibly the question comes to one’s mind: what if that person was a beloved relative of mine…or even myself?

I encountered a few errors: p. 67 the legend to Figure 5.2B reads “12 blackened seats” where only 11 are blackened; p. 180, line 4 reads “than” where then is intended; p. 195 “de minimus non curat lex” employed twice should be de minimis … . Although I do not want to be labeled sexist I found rather disconcerting the exclusively repeated use of “she” and “her” to indicate the patients’ examining physician. A more balanced and natural concession could have been made by using s/he and her/his.

Bibliography is signaled numerically within the text and annotated at the end of each chapter. An appendix contains “a brief primer on statistical approaches for quantifying uncertainty”. At the beginning of the book there is a list of abbreviations used throughout. At the end there is a glossary and a comprehensive index.

Even in professional publications and, needless to say pharmaceutical adverts and media reports, many health benefits and risk assessments are presented as authoritative, definitive and based on compelling evidence. This book points out that “[H]owever, all they provide is the illusion of certainty”. This volume makes for easy reading and will help the average person “interpret the daily flood of news reports or sometimes controversial studies”, but should also be of interest to professionals in medicine, nursing and public health, as well as government advisory and regulatory agencies, politicians, lawyers, engineers and academicians. It could also be used as additional information for selected undergraduate and graduate courses.

J.G. LLauradoDeputy Editor, MEQ