But several new reports released Tuesday show that some hours, days and seasons are riskier than others - often for reasons that are not entirely clear. Experts have been looking into these sorts of things since the mid- 1980s. By far the clearest finding, now confirmed by at least 30 studies, is that morning is the riskiest time of day for the heart. Simply climbing out of bed substantially increases the danger of a heart attack, probably because it raises blood pressure, spikes stress hormones and makes the blood stickier, among other things. All of this amounts to more than a medical curiosity.
Doctors already know that beta blocker drugs can blunt the morning peak in heart attacks.
At the annual meeting of the American Heart Association in Dallas, researchers presented several new insights into how these risks fluctuate over time. Dr. Robert A. Kloner of Good Samaritan Hospital in Los Angeles reviewed 220,000 deaths in Los Angeles between 1985 and 1996. The risk began to climb sharply about Thanksgiving, peaked at New Year's and then gradually tapered off. January turned out to be the worst month. The risk was 33 percent higher than in the summer.