March 3, 2008

What Kind of Study Was That?

It is important to know if the information you are gathering on the Web is from a credible source.
If you are reading this, you already know that anyone looking for health and medical information is confronted by abundance. Every day the news and websites like this one provide a constant stream of information about medical conditions, treatments and the steps people can take to improve their health. Often, the information is contradictory — over a period of months, we might hear about one study that shows that drinking wine is good for your heart; another that shows that drinking wine makes women more likely to get breast cancer; and still a third that shows that sulfites in wine can cause a potentially fatal allergic reaction.

The goal of this two-part series is to make you an informed consumer of health information.

So, how do you sift through the information and figure out which of these studies is right? Most likely, they all are, at least in some specific way. If they appear to have different results, the probable reason is that they are different kinds of studies that were designed to answer different questions. The mere fact that each is "scientific" tells us very little about what they mean for us as individuals.

Understanding the types of studies reported in health and medical articles can help you begin to evaluate their claims and make informed decisions.

In this first installment of TheDoctor's series on becoming an informed consumer of health information, we will talk about the three major types of research that are often referred to in news articles on medical discoveries — clinical trials, epidemiologic studies and population-based intervention trials. The second installment will discuss how you can figure out whether a health claim you read is credible or not. It discusses the terminology of scientific research and covers the strengths and weaknesses of the various types of medical studies as well as the kinds of conclusions that can honestly be drawn from them. The goal of this two-part series is to make you an informed consumer of health information.

Clinical Trials
Researchers will set up a clinical trial in order to test the effectiveness of a drug or other treatment for a particular disease or disorder. Essentially, a clinical trial is an experiment conducted within a hospital, lab or other controlled environment. For example, researchers might give a carefully screened group of subjects a new allergy medicine and then observe or test their reactions. Subjects need to be carefully screened so that unaccounted-for differences in people do not influence the results. For example, if the study subject group includes people from widely varying age groups or health statuses, some unknown variable from their background — say, forgetfulness about taking pills or an unknown interaction with an over-the-counter medication or ethnic food — might be mistaken for an effect of the drug. Clinical trials are good at establishing cause-and-effect relationships — for instance, proving that diets low in folic acid can cause certain birth defects.

The down side of a clinical study is that its artificiality might mask an effect that would arise in people's real lives. For example, many years ago, an antidepressant drug passed several clinical trials with flying colors, only to have it discovered that it seriously interfered with specific kinds of intellectual performance. The scientists running the clinical trials had tested the drug for all kinds of common side effects — headache, nausea, dehydration and others — but had never thought of testing its effect on activities such as playing chess or solving mathematical problems. Because what they test is usually focused on a specific intervention for a specific problem, clinical trials may need to be repeated using different kinds of subjects before their results can be applied to the general public.

Epidemiological Studies
These are often the studies behind the big pronouncements we hear about on the news. The findings of a study that says eating chocolate improves mood are likely to be based on a questionnaire or other means of gathering information in which people's mood and their chocolate consumption are measured. Epidemiological studies are not performed in a laboratory setting; they usually take place in the real world and involve large numbers of people.

The famous Framingham Heart Study, for example, followed over 5,000 men and women living in a Massachusetts town, from the 1940s through the 1970s. The researchers asked subjects/participants such things as if they smoked, how much education they had, how much meat they ate and then related this information to the health of their hearts. This kind of study can identify subtle trends that affect large numbers of people. For example, it might show a clear association (called a correlation) between smoking, masculinity and heart disease. The problem comes with trying to evaluate which, if any, of these three is a cause and which is an effect. Does smoking cause heart disease? Is it more likely to cause heart disease in men? Or are men both more likely to develop heart disease for dietary reasons and more likely to smoke for cultural reasons? Epidemiological studies might point to a plausible cause and effect, but it usually takes an experiment or clinical study to provide real proof.

Population-based Intervention
Sharing some characteristics of an epidemiologic study and some of a clinical trial, a typical population-based intervention trial looks at large numbers of people living outside a controlled setting, who are given either a real treatment (the "experimental" group) or a fake treatment or placebo such as a sugar pill (the "placebo" group) and then observed to see whether a specific outcome occurs in one group or the other. A well-known example of a population-based intervention is a 2002 study of hormone replacement therapy (HRT), which involved 16,000 postmenopausal women. This study had to be stopped when researchers noticed that the women taking a certain hormone combination were developing cancer and suffering strokes at an increased rate. Population-based interventional studies can be very useful for detecting small trends that show up in large groups of people; they also have the advantage of reflecting real people's daily lives. The flip side is that, because the circumstances of the study are not carefully controlled, it cannot clearly establish what causes a particular effect or account for all the variables that may affect all the various outcomes. These variables might include differences in such things as people's diets, their level of exercise and other habits as well as the accuracy with which they report these things. Many studies have seen their results skewed by subjects' inability to accurately report such things as OTC drug use, medical history and eating habits.

The bottom line for consumers of scientific and medical news is that, armed with a little knowledge, we can be go beyond the headlines and the hype and glean useful information that can help us lead healthier lives. Learning to read between the lines of news reports and sift science from pseudoscience is one of the most powerful health strategies you can exercise.

Pop Quiz
Answer the following questions and let's see what you learned from Part One.
  1. Five thousand Eskimos of all ages were studied for 10 years. Everything they ate was recorded using daily food diaries and they were tested every six months for signs of heart disease and diabetes. A strong association was found between a diet high in animal fat and both heart disease and diabetes. What kind of study was this?

    1. Population-based Intervention
    2. Epidemiological Study
    3. Clinical Trial

  2. 75 Eskimo men between 45 and 60 were given a new cholesterol-lowering drug in a laboratory setting. They ate an identical diet, which was provided at the lab. For 6 months, at one-month intervals, the men were tested for cholesterol levels.

    1. Population-based Intervention
    2. Epidemiological Study
    3. Clinical Trial

  3. 700 Eskimo men and women were divided into two groups. One group was put on an exercise regimen for a year; the other group was not. Both groups ate an identical diet. All subjects were tested every week for BMI.

    1. Population-based Intervention
    2. Epidemiological Study
    3. Clinical Trial

Answers: 1. B; 2. C; 3. A
NOTE: We regret that we cannot answer personal medical questions.
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