relatively abrupt turn to a very steep downslope as one nears the age of death of the ideal Gaussian curve, and a final flattening of the curve as the normal biological distribution of deaths results in a tail after the age of 90….
Thus, two profound characteristics of the mortality of man, the elimination of premature disease and the development of the sharp downslope representing natural death, have remained far from the public consciousness. These data have been available for many years. The first solid comments about rectangularization of the human survival curve can be found in prophetic statements in the 1920s. Many statisticians and actuaries working with national health data since that time have noted the increasingly rectangular shape of the curve, and many have speculated that it represents a natural species life limit. Entire theories of the aging process … have been built around the observed fact of a natural life span in man and animals. Yet, the public has remained largely ignorant of these developments.
A society in which life expectancy is believed to increase at every age and in which one becomes increasingly feeble as one grows older is a society heading for trouble. A society moving according to the curves of Figure 5, as our society is, is a society moving toward a world in which there is little or no disease, and individuals live out their natural life span fully and vigorously, with a brief terminal period of infirmity…. Dramatic changes in mortality patterns result in equally dramatic social changes.
Figure 4 Sequential Survival Curves in the United States
Source: U.S. Bureau of Health Statistics.
Figure 5 Ideal Mortality Curve in the Absence of Premature Death
Source: U.S. Bureau of Health Statistics.
References
Cannon, W. B., The Wisdom of the Body, New York: Norton, 1932.
Dubos, R., Man Adapting, New Haven, CT: Yale University Press, 1965.
Sacher, G. A., “Life Table Modification and Life Prolongation,” in J. Birren and C. Finch, eds., Handbook of the Biology of Aging, New York: Van Nostrand Reinhold, 1977, pp. 582–638.
Source: Vitality and Aging: Implications of the Rectangular Curve by James F. Fries and Lawrence Crapo. New York: W. H. Freeman, 1981. Reprinted by permission of the authors.
Reading 7: The Compression of Morbidity Hypothesis
A Review of Research and Prospects for the Future
Vincent Mor
Cross-national evidence for the validity of the compression of morbidity hypothesis originally proposed by Fries is generally accepted. Generational improvements in education and the increased availability of adaptive technologies and even medical treatments that enhance quality of life have facilitated continued independence of older persons in the industrialized world. Whether this trend continues may depend upon the effect of the obesity epidemic on the next generation of older people.
For more than 2 decades, gerontologists have been debating the implications of the progressive reductions in old-age mortality and increasing survival of the very old, with some noting that lengthening life necessarily extends the duration of functional dependency in an aging population. It has been hypothesized that increasing survival does not necessarily mean that the added years of life accruing to older individuals would be spent sick and disabled.1 This compression of morbidity hypothesis stated that better health care, an active lifestyle, and greater preventive health behavior would preserve health even in the face of increasing survival. Shortly thereafter, other researchers2 were able to quantify “active life expectancy,” setting the stage for the application of sophisticated demographic techniques to test the hypothesis that the duration of morbidity and disability would not increase or might even be reduced in the population, even as mortality was decreasing….
There are several important clarifications that should be made to better understand the dispute surrounding the compression of morbidity hypothesis. First, using morbidity and disability interchangeably ignores the evidence that the presence of different diseases may have quite different effects on mortality, hospitalization (a health services use-based marker of real morbidity), disability, and functional impairment.9 For example, although cardiovascular disease mortality declined, partially because of improved treatment, outreach efforts also led to earlier identification of more individuals with early-stage disease. Earlier detection of disease (morbidity) is one reason why increases in the prevalence of chronic illness have not translated into increases in disability and impaired function.10,11 …
Efforts to understand what has caused the reduced rate of functional decline in the aged population have focused on the improved education of the newer cohorts of elderly, improvements in the built environment (e.g., barrier-free housing, elevators) and material amenities, and improvements in function-enhancing medical interventions.14 First, the average 75-year-old in developed countries of the 1990s is less likely to be constrained by stairs and more likely to have an automobile and to live in housing that is architechnally barrier free. Second, that same older person has his/her Social Security check directly deposited, meals warmed in a microwave, and groceries ordered over the telephone. Third, the disability of cataracts has been virtually eliminated with new surgical techniques, disabling arthritic hips and knees are routinely replaced, and improvements in the medical management of heart disease, for example, clearly facilitate retained functioning and independence. The relative contributions of each of these major classes of technological innovations to improvements in population functioning is not known, but it is likely that these, as well as other significant shifts in the lives of older persons in the industrialized world, have improved their quality of life and functional independence.6, 15 Indeed, it may be that the education advantage observed in most studies that find reduced functional decline is partially achieved by older persons being able to manipulate the environment without exertion.11
Nevertheless, before we celebrate and ignore the pending explosion of the aged population in all industrialized countries in the world, it is critical to understand that, even if the rate of functional decline has dropped several percentage points over the last decades, the sheer numerical increase in the size of the aged population over the next 30 years will mean that the number of older persons who are dependent, disabled, and suffering the functional consequences of multiple chronic conditions will be larger than it has ever been, far larger than most countries are prepared to manage. Healthy life expectancy (another expression of “active life expectancy”) is increased via reductions in mortality and morbidity, but disease prevalence is increasing, so functional independence must be maintained in the face of advancing age and comorbidity.11
The emerging epidemic of obesity among the middle-aged population, particularly in the United States, is another factor that may temper the optimism some have expressed about being able to compress the duration of functional morbidity.6, 15, 16 Recent evidence of the rising prevalence of obesity in the middle aged and the consequences of obesity for independence and for the ability to function and fill social roles suggests that we may be in for a reversal of the hard-fought gains of functional decline.12, 17–19 Indeed, these findings reinforce the importance of an active lifestyle and low-risk health
