Book Review
Wendy Wolfson
RedwoodAge.com

Understanding numbers is often a high stakes matter, when it comes to the health choices we must make. Available information is frequently incomplete and often confusing. Sometimes it is deliberately intended to be so, in the case of direct-to-consumer advertising  to induce people to ask their doctors for the latest drug.  

"Know Your Chances," a primer on healthcare decision making written by a trio of docs from the Dartmouth Outcomes Group, cuts through ambient dreck to give the average person the dirt on statistics.

For several years, Drs. Steven Woloshin, Lisa Schwartz and Gilbert Welch have trained hundreds of journalists how to report on healthcare in a class sponsored by NIH called "Medicine in the Media."

Now they share these basic tools with you, so you can learn the fine art of deciphering drug ads, detect bias, pick out the hype in medical stories and. as a result, make better decisions about your health.

The trio teach you the important questions to ask, and in a clear and friendly way, how to do the (quite elementary) math. 

This how-to guide to health statistics makes you think about medical outcomes in a whole new way. For example, a new expensive cancer drug may shrink a tumor but may not prolong a patient's life.

Another, now classic example, was hormone replacement therapy. HRT was all the rage for several years until researchers tallied the numbers in the Women's Health Study and found to their chagrin, that while taking estrogen raises the level of HDL, the "good" cholesterol, which is associated with lower heart attack risk, the absolute number of women who had higher HDL levels actually had a higher incidence of heart attacks. Not hugely higher, but just enough for doctors to stop recommending hormone replacement therapy.  

Questions the book covers include:

• What is risk? - How to understand what an outcome means, whether it's a symptom, a disease or death.
• How big is the risk? What are your personal chances of experiencing an outcome over a period of time? Is it over a lifetime or is it a year?
• How to best to phrase risk. How to recalculate confusing risk equations into an easy-to-understand form.
• How to define risk. Is a probability absolute or relative?
• How to figure out if the risk mentioned actually applies to you.
• How does pne risk stack up to other risks. Why that drug may help you sleep but give you worse side effects than insomnia. 
• Figuring out what risk reduction really means. Does a drug or procedure actually reduce your risk or just lessen your symptoms?
• Weighing the downsides of risk reduction. Is the risk reduction benefit worth potential side effects and cost?
• How to evaluate the science and studies behind the numbers. They are not always easy to determine.

This  book goes down smoothly as a chocolate milkshake, almost qualifying as beach reading, but you will want to do the brain teaser exercises. 

In a last, somewhat tongue-in-cheek exercise, Woloshin, Schwartz and Welch subject their book to the same rigorous testing as any other medical intervention.

They tally up the numbers and conclude reading their book certainly made people smarter, and caused no harm. And they show statistical proof.