如果说,在过去的20年由于心脏病而死亡的人数的下降是医学的一大成就,那么,什么原因导致这种下降则成了目前医学的主要论题之一。据心脏病学家的计算,从1968年以来,这种下降延长了50万以上美国人的生命。对于其中某些人,可归因于低脂饮食、减少吸烟,降低血压和增加体育运动;对另一部分人则可归功于医疗保健服务。然 If the decline in the number of people who died of heart disease over the past 20 years is a medical achievement, then what has led to this decline has become one of the major topics in medicine so far. According to cardiologists, this decline has prolonged the lives of more than 500,000 Americans since 1968. For some of them, it can be attributed to a low-fat diet, reduced smoking, lower blood pressure and increased physical activity; for others, health care services. Of course