is little basis for concluding that levels or trends in the quality of social networks have played a role in the divergent life expectancies studied. Similarly, little evidence supports the hypothesis that hormone therapy played a part in an emergent longevity shortfall for American women.

Finally, the panel examined whether differences in health care systems across countries might help explain the divergence in life expectancy over the past 25 years. The health care system in the United States differs from those in other high-income countries in a number of ways that conceivably could lead to differences in life expectancy. Certainly, the lack of universal access to health care in the United States has increased mortality and reduced life expectancy. However, this is a smaller factor above age 65 than at younger ages because of Medicare entitlements. For the main causes of death at older ages—cancer and cardiovascular disease—available indicators do not suggest that the U.S. health care system is failing to prevent deaths that would elsewhere be averted. In fact, cancer detection and survival appear to be better in the United States than in most other high-income countries. Survival rates following a heart attack also are favorable in the United States.

Most of the comparative data the panel reviewed relate to the performance of the U.S. health care system relative to those of other high-income countries after a disease has already developed. A separate concern is that the U.S. health care system does a particularly poor job at prevention, an observation that may be especially relevant in the midst of a nationwide obesity epidemic. The panel reviewed scattered evidence on the performance of the United States with respect to preventive medicine relative to European countries and found the evidence to be inconclusive. Certainly the high prevalence of certain health conditions in the United States is consistent with a failure of preventive medicine. But it could also be consistent with a higher prevalence of smoking, obesity, and physical inactivity among Americans, or with a medical system that may be unusually effective at identifying certain diseases.

LOOKING TO THE FUTURE

What will happen to life expectancy rates in the United States and other countries in the coming decades? Although it is impossible to answer that question with any certainty, the analyses described in this report point to some likely patterns for the future. Because there appears to be a lag of two to three decades between smoking and its peak effects on mortality, one can predict how smoking will affect life expectancy in various countries over the next 20 to 30 years. On this basis, life expectancy for men in the United States is likely to improve relatively rapidly in the coming decades in response to changes that have occurred in smoking patterns over the past 20 years. For



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement