[coldpie]

This is exactly the kind of question the trials are designed to answer, yes. We know roughly the background incidence rate of diseases, so you can expect some percentage of participants will be affected by those diseases. It's also important to remember your basic statistics fallacies: the question is not, what are the odds that any of our participants come down with MS, which is a very tiny chance. The question is, what are the odds that any of our participants will come down with _any_ background disease, which is a much larger chance. It is very likely to happen, and indeed it does. They still pause the study to run the numbers and make sure the new diagnoses are not outliers from the background rate.