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There are several types of medical research. Some studies are done to learn what causes disease, and how to avoid getting sick. Others are done to improve how we treat disease. They include the following: Observational studies follow the same group of people over time to find out what happens to their health. An example is the Framingham Heart Study, in which 5,209 men and women between the ages of 30 and 62 from the town of Framingham, Massachusetts have been studied since 1948. This study was the first to show that having high levels of cholesterol and blood pressure, as well as cigarette smoking and other factors, put you at risk of heart disease. Epidemiological studies look for patterns of diseases in large groups of people. For example, every year, doctors do epidemiologic studies to look at what kinds of influenza (flu) outbreaks have occurred in the world. They then use this information to decide what to put in that year's flu vaccine. Intervention studies look at ways to change behaviors that affect health. One example would be a study of how increased exercise affects weight and diabetes or heart disease. Prevention studies look for ways to keep people from getting sick. These studies often involve people who are at risk for a particular disease. An example is a study of people who smoke or have high blood cholesterol, which puts them at risk for having a heart attack. If the prevention method is a drug or vaccine, prevention studies are clinical trials (see below). If the prevention method is a change in behavior, they are intervention studies. Clinical trials are performed to learn the best ways to treat or, sometimes, to prevent disease. This kind of study tests a new drug, vaccine, or medical device. In the United States, companies are required to prove to the Food and Drug Administration (FDA) that treatments are both safe and effective before they can be sold in pharmacies. Clinical trials begin only after results from laboratory and animal studies show that the new, investigational treatment is safe to test and likely to be effective in people. Volunteers in clinical trials are closely monitored to look for both the expected effects of the investigational treatment, and side effects. Clinical trials are done in stages, which are called phases. If you are thinking about volunteering for a clinical trial, you should know which phase of testing the drug or device is in. Phase I clinical trials last up to one year and involve 20-100 healthy volunteers. The primary purpose of Phase I studies is to determine the best dosage to be used in further testing, and to measure how quickly the drug is broken down in the body. Phase II clinical trials usually last one to two years and involve up to several hundred volunteers who have the condition to be treated. The primary purpose of Phase II trials is to find out if the investigational treatment has the desired effects in people, to confirm the best dosage to be used in further testing, and to begin testing for safety. Phase III clinical trials typically last two to four years and involve several hundred to several thousand volunteers. The main purpose of Phase III trials is to measure how well the investigational treatment works and to determine how much of a drug is needed to achieve the best result. This is usually the phase when the investigational treatment is being compared to a placebo (inactive treatment) or to the treatment that is presently used (standard treatment). Phase IV clinical trials, sometimes called "post-marketing" trials, begin after the results of the Phase I - III trials have been given to the FDA for approval. They last two to ten years and involve several hundred to several thousand patients. Phase IV trials are done for many different reasons - to test different dosages, to determine if the treatment works for other diseases or conditions, or to test different ways of taking the treatment (such as different forms of drugs - tablets, capsules, "time-release" tablets, syrups).
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