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? How
should we interpret the daily flood of news reports on
sometimes contradictory
medical studies?
A new book, co-written by a Johns Hopkins professor
and an outside
colleague, seeks to examine health questions like these in
a new light. Authors
Erik Rifkin and Edward Bouwer are not physicians; both are
environmental
scientists with decades of experience in analyzing health
risks connected with
air, water and soil pollution. By directing this expertise
at data from
mainstream medical studies, the researchers believe they
have found a fresh way
to help the average reader assess common health risks.
Their findings are described in The Illusion of
Certainty: Health Benefits
and Risks, published by Springer. Bouwer is a professor
and chair of the
Department of Geography and Environmental Engineering
at Johns Hopkins. Rifkin
is president of an environmental consulting firm in
Baltimore. A chapter called
"The Physician's and Patient's Perspective" was written by
Bob Sheff, a
radiologist who trained at UCLA and Johns Hopkins.
The researchers said they wrote the book because they
believe that the
average person who must make critical decisions about
health risks is not
getting a complete picture. They discovered that
health-related choices that
sometimes sound straightforward and obvious are often much
more uncertain and
controversial when the risk statistics are viewed in a
different way.
"I've been involved in human health and environmental
risk assessment for
more than 30 years," Rifkin said. "It became clear to me
during this time that
the uncertainty in health risk assessment had gotten lost,
and the numbers had
taken on a life of their own"
He had collaborated with Bouwer on projects for 20
years, and the two
decided to train their science skills on data from medical
studies. "I can read
scientific articles, and I've had experience handling
epidemiological data,"
Bouwer said. "You can look at the data in medical studies
the same way you look
at environmental data. We did, and we found that there was
a lot of uncertainly
in these studies, but it often wasn't being communicated to
people."
Much of this misinformation, the researchers said,
comes from the way risks
are explained to a patient or described in a news story.
One measure, called
absolute risk reduction, looks at the difference in death
rates between two
groups, such as one group who received a medication and one
who did not. If one
person among 100 people who took medication died, the death
rate would be 1
percent. If two people died among 100 people who did not
take medication, the
death rate for that group would be 2 percent. The
difference between these death
rates, found by subtracting 1 percent from 2 percent, would
yield the absolute
risk reduction: 1 percentage point.
But the authors learned that drug companies,
journalists and some medical
professionals often rely on a different measure: relative
risk reduction. This
term compares only the raw numbers of people who died in
each instance. In the
above example, because half as many people (one vs. two)
died in the group who
took the medication, the relative risk reduction is 50
percent. By this measure,
the patient can be told that his or her chance of dying is
cut in half by taking
the drug, instead of being told that there was only a 1
percentage point
difference in the treated group.
"It's as if, in hearing about a baseball game between
the Orioles and the
Yankees, you're told that the Orioles scored twice as many
runs as the Yankees,"
Rifkin said. "But if you don't know the actual numbers
involved, you don't know
whether this was a close 2-1 game or a 20-10 rout. If you
don't know where
you're starting from, the relative risks figures will not
be helpful."
In their book, Bouwer and Rifkin argue that although
relative risk is a
useful yardstick for research scientists, "it should not be
used by the public
to assess the risks and benefits of screening tests. Far
more weight should be
given to absolute risk reduction values."
The authors give readers an easy way to visualize the
absolute risk numbers
through a graphic called the Risk Characterization Theater.
This diagram is
patterned after a seating chart for a theater with space
for 1,000 people. The
authors darken the "seats" that represent the number of
people who are likely to
benefit from a screening test or a medication or who may be
at increased risk
from exposure to an environmental contaminant.
"These theater charts make it easier for people to see
what the case
studies are referring to," Bouwer said. "We're trying to
give people some new
tools to help them make better informed decisions about
health risks."
Various chapters in the book focus on topics such as
environmental
contaminants, prostate screening, cholesterol, statin
drugs, smoking,
chlorinated drinking water and exposure to residential
radon. The authors said
their intent is not to offer medical advice but to show
readers another way to
evaluate health risks.
In the book's foreword, Jared L. Cohon, president of
Carnegie Mellon
University, says Rifkin and Bouwer have been "courageous in
writing this book.
In going to the heart of what's been lacking in risk
communications and
management, they have taken on established thinking. As a
result, this book may
be controversial. In my view, a book like this is long
overdue, and we all will
be better for the reflection and debate it is likely to
stimulate among
scientists and policy-makers."
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