Understanding Medical Studies : Risks

by National Institute on Aging

(Page 2 of 2)

Absolute risk

Absolute 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 work

How 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 using a drug to prevent further bone loss leading to osteoporosis. Several different drugs 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 worse (absolute risk) for each medicine. Julia also needs to ask the doctor about side effects from each medication and her risk of those. With all this information, Julia can take part in making an informed decision about which drug to prevent osteoporosis is best for her to use at this time.

Ask yourself

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.

About the Author

www.nia.nih.gov
NIA, one of the 27 Institutes and Centers of NIH, leads a broad scientific effort to understand the nature of aging and to extend the healthy, active years of life. In 1974, Congress granted authority to form NIA to provide leadership in aging research, training, health information dissemination, and other programs relevant to aging and older people.