If you're worried about your heart, there's good news and bad. First the good: there is strong evidence to support the theory that a couple of beers or glasses of wine daily help to prevent coronary heart disease. Now, the bad part: most heart attacks occur at dawn. Researchers at Harvard Medical School and Boston's Brigham and Women's Hospital have provided the first solid clue to how alcohol works to protect the heart. After comparing the drinking habits of 340 men and women who had suffered recent heart attacks with those of healthy people of the same age and sex, the researchers found people who sip one to three drinks a day are about half as likely to suffer heart attacks as nondrinkers. Apparently, those who drank alcohol had higher blood levels of high-density lipoproteins, or the so-called good cholesterol, which is known to ward off heart disease. Meanwhile, researchers at the TNO Institute for Ageing and Vascular Diseases in Holland say most heart attacks occur in the early morning, when one would expect them the least because the heart is under little stress during that period. Researchers say the lack of a blood-clotting enzyme in the early morning hours could be one of the causes for the greater number of heart attacks around dawn (Global Technoscan, October, 1993). The finding could have important implications for the treatment of heart patients, say scientists.