Four percent because people can't seem to have the discipline to got to bed a few minutes early when the time change is coming. Your own link said it was not directly because of DST but rather lack of sleep stressing the body. Also to say that it is an extra 60,000 heart attacks is laughable. If people are having a myocardial incident prompted by one hour of sleep they are a ticking time bomb that is just waiting for the next time they stay up late to watch a game or go out for dinner and drinks. If they aren't having them the Monday after DST starts they are likely having them soon thereafter.There is no reason for it, just a needless thing that has arisen because some lawmakers thought it was a good idea to save fuel.
And a 4% net difference is significant. Let's see 1.5 million heart attacks each year in the US. 4% of those because of some time shifts would be an extra 60,000 heart attacks that may be unnecessary. Just pick a time and stick with it all year and don't change it each spring and fall.