Exactly where we will stand in the long war against disease by the year 2050 is impossible

to say. (111) But if developments in research maintain their current pace, it seems likely that a combination of improved attention to dietary and environmental factors, along with advances in gene therapy and protein-targeted drags, will have virtually eliminated most major classes of disease.

From an economic standpoint, the best news may be that these accomplishments could be accompanied by a drop in health-care costs. (112) Costs may even fall as diseases are brought under control using pinpointed, short term therapies now being developed. By 2050 there will be fewer hospitals, and surgical procedures will be largely restricted to the treatment of accidents and other forms of trauma (外伤). Spending on nonacute (慢性病的) care, both in nursing facilities and in homes, will also fall sharply as more elderly people lead healthy lives until close to death.

One result of medicine's success in controlling disease will be a dramatic increase in life expectancy. (113) The extent of that increase is a highly, speculative matter, but it is worth noting that medical science has already helped to make the very old (currently defined as those over 85 years of age) the fastest growing segment of the population. Between 1960 and 1995, the U. S. population as a whole increased by about 45%, while the segment over 85 years of age grew by almost 300%. (114) There has been a similar explosion in the population of centenarians, with the result that survival to the age of 100 is no longer the newsworthy feat that it was only a few decades ago. U. S. Census Bureau projections already forecast dramatic increase in the number of centenarians in the next 50 years: 4 million in 2050, compared with 37, 000 in 1990.

(115) Although Census Bureau calculations project an increase in average life span of only eight years by the year 2050, some experts believe that the human life span should not begin to encounter any theoretical natural limits before 120 years. With continuing advances in molecular medicine and a growing understanding of the aging process, that limit could rise to 130 years or more.

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