1. Awful summary 0.6% recurrent event rate does not mean it was 99.4% effective. You need to know what the recurrent event rate would have been if everything e

1. Awful summary 0.6% recurrent event rate does not mean it was 99.4% effective. You need to know what the recurrent event rate would have been if everything else was the same and they hadn't followed the diet. Hint: if the normal recurrent event rate is 0.3% then they are worse off, not better (insert test of statistical significance here). If the event you are testing for (recurrent CVA) is rare, then a large enough sample and proper statistical significance tests are even more important. 2. No control group "Didn't follow the diet" is not a control group. They have, post-hoc, selected the subgroup consisting of "people unlikely to follow a lifestyle intervention". That group might also been the most likely to continue smoking, not take their medication, do no exercise, be too unwell to follow a rigorous diet, etc etc. 3. Subgroup analysis Drawing a circle around a subgroup after your study and making inferences from them is an excellent way to get bogus results. (Classic example: Wimbledon winner prediction system. Email 2000 people at random with each player and ask them to bet $1 on that player. After you know the winner, get the subgroup of people who won, and ask them how accurate they think your winner prediction system is.)