How can you test preventive measures for a medical condition?
In principle, preventive measures should be tested in the same way as treatments are tested – in randomized controlled trials. But this is often difficult. For example, to find out whether getting more exercise and eating low-calorie and low-fat foods can help to prevent diabetes, the following would have to be done:
- A large number of healthy people would have to be willing to be randomly assigned to a group that changes their diet and participates in a sports program for years, or to a control group that is not instructed to do so.
- These people would have to be monitored for decades to notice any health-related differences later on.
Randomized trials on the prevention of medical conditions in healthy people involve a lot of time and effort. Because of this, these kinds of studies often look at smaller groups of people who are already at a greater risk of developing the condition instead. In the case of type 2 diabetes, that means people over the age of 45 who are overweight or already have slightly increased blood sugar levels. Randomized trials for this group of people have already been completed, looking into how lifestyle can affect their diabetes. The results suggest that type 2 diabetes can't be prevented completely by making adjustments to your lifestyle, but it could be delayed at least. So the doctor's advice that Mr. Miller get more exercise and change his diet is based on scientific evidence.