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		Understanding Risk: What Do 
          Those 
          Headlines Really Mean?
              Every day in the newspaper or on television we 
                see stories about new medical findings. Perhaps we hear that a 
                certain drug causes a 300% or 3-fold increase in strokes. That’s 
                a large increase—it sounds scary. But, if you know that in every 
                10,000 people not taking the drug, there are 2 strokes, then a 
                3-fold increase really only means 6 more strokes. Maybe that’s 
                not quite so frightening. It’s also confusing that sometimes stories 
                seem to report opposite results—a new vaccine prevents a devastating 
                infection, or it doesn’t. How are we to make sense of such stories? 
                How do we know what to believe?
              This fact sheet provides some background to help 
                you understand these news reports. It might also help you judge 
                which results are really important and which are simply interesting 
                but not a reason to change how you take care of yourself.How does a research study begin?First, you should know that there are different 
                types of research studies. Often a scientist starts with a question 
                and sets up a controlled experiment to get the answer. Maybe a 
                new drug needs to be tested to see if it cures a bacterial infection. 
                In this kind of experiment the scientist grows the bacteria in 
                the laboratory and then adds the new drug to see what happens. 
                Usually, there is also a control—that is, the same bacteria 
                is grown but not exposed to the new drug. The scientist then looks 
                to see how the new drug affected the treated bacteria compared 
                with the untreated bacteria. Perhaps the treated bacteria are 
                dying while the control ones are still growing. That could mean 
                the drug is effective. If so, the scientist might move on to testing 
                the drug in animals and then in people.Which studies involve people?When studying people, scientists often use observational 
                studies. In these, researchers keep track of a group of people 
                for several years without trying to change their lives or provide 
                special treatment. This can help scientists find out who develops 
                a disease, what those people have in common, and how they differ 
                from the group that did not get sick. What they learn can suggest 
                a path for more research. However, observational studies have 
                certain weaknesses. Sometimes differences between groups are caused 
                by something the investigators are not aware of. For any observational 
                study, only further research can prove for sure whether their 
                finding is the actual cause of illness or not.What comes next?The results of laboratory experiments and observational 
                studies often interrelate. For example, perhaps a new drug for 
                lowering cholesterol has already been tested for safety in a controlled 
                experiment. Scientists know from observational studies that eating 
                a lot of high-fat foods can raise cholesterol levels and they 
                know that people with high cholesterol are more likely to have 
                heart attacks. This might lead scientists to suspect that they 
                can prevent heart attacks by lowering cholesterol levels with 
                the new drug.But how to prove that this suspicion is correct? 
                Another kind of research study, called a randomized controlled 
                clinical trial (RCT), is thought to be the best way to learn 
                whether a certain treatment works or not. A clinical trial 
                often involves thousands of human volunteers. They are assigned 
                to 2 or more study groups by chance (randomized). One of 
                the groups, the control group, receives a placebo. 
                A placebo looks just like the treatment or drug being tested, 
                but actually does nothing.To start the clinical trial the scientists sign 
                up volunteers. The volunteers are randomly divided into two groups. 
                One receives the test drug, and the other, the control group, 
                gets a placebo. The study is also masked. This means that 
                neither the doctors nor the volunteers know who is getting the 
                test treatment or the placebo. For the next several years the 
                investigators keep track of cholesterol levels and heart attacks 
                in each group. They also watch for side effects of the drug. At 
                the end of the study period, everyone learns which group was getting 
                the test drug and which was on placebo, and the results are analyzed. 
                Fewer heart attacks in the group receiving the test drug would 
                show that the drug prevents heart disease.How Do They Explain the Results?But, how well does this fictional drug prevent 
                heart attacks? We have to look at how it affects someone’s risk 
                of heart attack. By studying large numbers of people, scientists 
                can learn how big these effects are. Benefits and risks can be 
                explained in several ways. These include relative risk 
                and absolute risk.When the difference between two groups is described 
                as “relative,” it is usually shown as a ratio or a percent. An 
                “absolute” difference is nothing more than a number found by subtraction. 
                How this number is presented to you can sway how you “feel” about 
                the finding and affect whether you change your behavior.Let’s look at these differences first by using 
                dollars. We’ll compare Chris and Pat’s retirement accounts.Chris		        Pat

Account balance	        $130,000	        $100,000
Relative difference	30% more than Pat
Absolute difference	$30,000 more than Pat
              Think about how the numbers make you feel. Would 
                you rather say that “I have 30% more than Pat” or that “I have 
                $30,000 more than Pat?” Both statements report the same finding, 
                but different people prefer to use different ways to present the 
                results.If we drop the account balances, would you answer 
                differently?Chris		        Pat

Relative difference	30% more than Pat	
Absolute difference	$30,000 more than Pat
              Relative RiskLet’s look again at our earlier research example. 
                In describing the results, the scientist might talk about relative 
                risk. This compares the likelihood that a person who takes 
                the new medicine will have a heart attack to the likelihood that 
                a person in the placebo group will have one. It tells us how much 
                larger or smaller the chance of heart attack is while using the 
                test drug. Maybe the researchers found the relative risk of heart 
                attack in the placebo group was “1.5.” Since a finding of “1.0” 
                means there is an equal chance in each group, the finding of 1.5 
                means the chance of heart attacks in the group receiving 
                the placebo is 50% greater than the chance of heart attacks 
                in people taking the test medicine. It does not mean half 
                of all those who did not receive the test drug had heart attacks.Absolute RiskAbsolute risk gives an actual number of 
                health problems that happened or are prevented because of the 
                drug. In our imaginary study of a new cholesterol drug, let’s 
                say that there might be 50 heart attacks in 10,000 people taking 
                the drug and 75 heart attacks in a similar group taking the placebo. 
                That is, for every 10,000 people not using it, there would probably 
                be 25 more heart attacks. That’s the absolute risk. Some people 
                find absolute risk--“X number of extra cases in 100, 1000, or 
                10,000 people”--easier to apply to their own health care decisions 
                than a relative risk percentage.Let’s Put “Risk” to WorkHow would someone use risk information when talking 
                with his or her doctor about a health problem? Here’s an example. 
                Recently Julia learned that she has osteopenia, a loss of bone 
                mass that can develop into osteoporosis. Exercising and getting 
                more calcium and vitamin D are slowing her bone loss. But, her 
                doctor has suggested a drug to prevent further bone loss leading 
                to osteoporosis. Several choices are available. She should ask 
                her physician how well each one would probably lower her chance 
                of breaking a bone as she grows older. The doctor might be able 
                to give her a percentage (relative risk) or the number of times 
                people in the group get sick (absolute risk) for each medicine. 
                Julia also needs to ask the physician about side effects from 
                each medication and her risk of those. With that information, 
                she can take part in making an informed decision about which drug 
                to prevent osteoporosis is best for her to use at this time.Ask YourselfSo, when you learn about a new medical finding, 
                ask yourself:1. Was it a study in the laboratory, in animals, 
                or in people? The results of research in people are more likely 
                to be meaningful for you.2. Does the study include enough people like you? 
                You should check to see if the people in the study were the same 
                age, sex, education level, income group, and ethnic background 
                as yourself and had the same health concerns.3. Was it a randomized controlled clinical trial 
                involving thousands of people? They are the most expensive to 
                do, but they also give scientists the most reliable results.4. Where was the research done? Scientists at a 
                medical school or large hospital, for example, might be better 
                equipped to conduct complex experiments or have more experience 
                with the topic. Many large clinical trials involve several institutions, 
                but the results may be reported by one coordinating group.5. Are the results presented in an easy-to-understand 
                way? They should use absolute risk, relative risk, or some other 
                easy-to-understand number.6. If a new treatment was being tested, were there 
                side effects? Sometimes the side effects are almost as serious 
                as the disease. Or, they could mean that the drug could worsen 
                a different health problem.7. Who paid for the research? Do those providing 
                support stand to gain financially from positive or negative results? 
                Sometimes the Federal government or a large foundation contributes 
                funding towards research costs. This means they looked at the 
                plans for the project and decided it was worthy of funding, but 
                they will not make money as a result. If a drug is being tested, 
                the study might be partly or fully paid for by the company that 
                will make and sell the drug.8. Who is reporting the results? Is the newspaper, 
                magazine, or radio or television station a reliable source of 
                medical news? Some large publications and broadcast stations have 
                special science reporters on staff who are trained to interpret 
                medical findings. You might want to talk to your health care provider 
                to help you judge how correct the reports are.The bottom line is--talk to your doctor. He or 
                she can help you understand the results and what they could mean 
                for your health. Remember that progress in medical research takes 
                many years. The results of one study need to be duplicated by 
                other scientists at different locations before they are accepted 
                as general medical practice. Every step along the research path 
                provides a clue to the final answer—and probably sparks some new 
                questions also.
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