Your Medical Mind_ How to Decide What Is Right for You - Jerome Groopman [8]
This statistic comes as a surprise to many people. When you hear that a statin lowers Susan’s risk by 30 percent, it sounds as if she is at 100 percent risk of suffering a heart attack if she doesn’t take the medication. The calculation above yielded what is called the “number needed to treat,” how many people must be treated to benefit one person in the group; for women like Susan, three hundred have to take a statin in order to help one person. By calculating the “number needed to treat,” you can clearly grasp the impact of the drug for an individual.
A second key aspect of health literacy is knowing how the same information can be presented as either positive or negative. This way of changing how information is presented is known as “framing.” We first framed the benefit of statin treatment by presenting it as a 30 percent reduction in risk. Seen this way, the benefit of taking statins appears very significant. But by reframing the benefit as the question “How many people do you need to treat to protect one person from a heart attack?” the benefit may seem relatively minor. Still, some people look at it this way: “If there is a chance I could be the one person out of three hundred who avoids a heart attack, then the statin is 100 percent effective for me.”
“Decision aids” like the one Susan found on the Web site are designed to help people with a variety of medical conditions improve their health literacy. When you can interpret statistics accurately, you can merge science with stories and fit single anecdotes into the larger context of all people who are treated. Susan now knew the numbers relevant to her about statin treatment preventing a heart attack, and when we spoke, she considered whether she might be the one who would benefit. But she couldn’t stop thinking about the woman at church. Susan’s mind fixed on what she stood to lose.
The third component of health literacy is understanding the risks of a therapy. Susan’s acquaintance at church had the most common side effect of statins: muscle pain due to inflammation. The medications less often result in liver toxicity and gastrointestinal upset with abdominal pain and nausea. As Susan’s doctor told her, these side effects are seen in a “few percent” of patients. Statins cause muscle pain in 1 to 10 percent of people who take them. Some physicians believe you should drive down the LDL, or “bad” cholesterol, to very low levels by giving high doses of statins for greater protection against heart attack. But high-dose therapy with certain statins is more apt to affect the muscles. There is considerable controversy among experts over the risks and benefits of high doses of statins.
If we take into account both standard dose and high-dose statin treatment, we can accurately frame the side effects: The number affected is 1 to 10 out of 100. However, if we “flip” the frame, the number without any side effects is 90 to 99 out of 100, a much more reassuring statistic.
Susan continued to search on the government Web site. She read, “To find out what your risk score means and how to lower your risk for a heart attack, go to ‘High Blood Cholesterol—What You Need to Know.’” She had all her numbers from the doctor on her desk. She again followed the steps on the screen and found that she fit into category four—low to moderate risk. The guideline said that her goal was to lower her bad LDL cholesterol to less than 160 by starting a “TLC” diet: eating healthy foods and exercising regularly. Susan read further. If the cholesterol didn’t fall with diet and exercise, the guideline stated, “you may need medication.”
Susan sat back in her chair and looked at the screen