Small hours heart risk peak clue

"US scientists may have uncovered a reason why heart attacks and strokes occur most often in the early hours. The Emory University team say daily rhythms in the activity of cells that line blood vessels may be key. They found the activity of these cells was at its lowest ebb in the early hours of the morning. The study, presented to an American Heart Association conference, suggests this might make blood vessels less able to relax, raising the risk of problems" - BBC