WHAT IS THE TRUTH ABOUT HEALTH RISKS

Almost every day the TV is blaring warnings like:


TAKING THIS PILL WILL INCREASE YOUR RISK OF CANCER BY 30%



This scares a lot of people because they don’t understand what a 30%
increase in risk really means. If they did understand they wouldn’t give it a second thought. The actual risk in this case is 0.07% which is insignificant but the reader has no way of knowing that.

How can this be?


Very simple, for example a hypothetical study finds that big toe aches occur in 0.04%of people who watch TV. While only 0.02% suffer from toe ache who do not watch TV. So the headline would read “Watching TV increases the risk of big toe ache by 100%”.

A 100% increase sounds terrible until you find out that the number of people in the control group with toe aches was 2/10,000 and the numer in the TV group was 4/10,000. Then it is obvious that the actual increase is 0.02% and not 100%.

100% in this example is called a relative risk which is obtained by dividing the percent increase in the TV group, 0.02, by the percent in the control group, 0.02, which equals 100% ( 0.02/0.02 = 1 x 100 = 100%). Almost all medical studies of this type use this way of expressing percent and usually do not disclose the actual or absolute percent differences.

Knowing the difference between relative risk and the absolute risk is the key to understanding what the truth is behind the news release and relieving the anxiety induced by reading the scary headlines.