Correspondence
Aging, Health Risks, and Cumulative Disability
N Engl J Med 1998; 339:481-482August 13, 1998
- Article
To the Editor:
The concept of a compression of morbidity has implications for health care policies and costs and for the quality of people's lives. If morbidity can indeed be compressed into fewer years toward the end of a hypothetical “full life span,” the amount of disability over the whole life span will be reduced.
The paper by Vita et al. (April 9 issue)1 purports to provide evidence of such a compression. The authors state that “Not only do persons with better health habits survive longer, but in such persons, disability is postponed and compressed into fewer years at the end of life.” The accompanying editorial2 mentions some caveats — for example, that the sample is not representative of the general population. However, it also states that “at least in this cohort, the data support the controversial hypothesis of healthier aging with a compression of morbidity,” and that the study provides “the strongest support to date” for the compression hypothesis.
We present two hypotheses. If compression of morbidity occurs, the overall mortality rates of the group at high risk and of the group at low risk will be similar despite the high-risk group's having more morbidity. The alternative hypothesis is that for the low-risk group, morbidity and mortality tend to occur later, and the total amount of morbidity during life is similar to and might even be greater than that of the high-risk group. The results presented by Vita et al. show a 50 percent greater mortality for 10 percent or so of the sample. These results do not favor one hypothesis over the other. It should also be noted that if compression of morbidity had occurred, one could expect an increased mortality at ages approaching the hypothetical full life span. There is no evidence of this.
The study by Vita et al. is longitudinal, and hence it should be possible to test the hypotheses with data from this cohort as more people die. We believe that the current evidence concerning the hypothesis of general compression of morbidity is inconclusive, but such a compression may occur for specific diseases, such as Alzheimer's disease.3
3 ReferencesDan W. Harper, Ph.D.
W.F. Forbes, Ph.D., D.Sc.
Sisters of Charity of Ottawa Hospital, Ottawa, ON K1N 5C8, Canada1
Vita AJ ,Terry RB ,Hubert HB ,Fries JF . Aging, health risks, and cumulative disability. N Engl J Med 1998;338:1035-1041
Full Text | Web of Science | Medline2
Campion EW . Aging better. N Engl J Med 1998;338:1064-1066
Full Text | Web of Science | Medline3
Stern Y ,Tang MX ,Devaro J ,Mayeux R . Increased risk of mortality in Alzheimer's disease patients with more advanced educational and occupational attainment. Ann Neurol 1995;37:590-595
CrossRef | Web of Science | Medline
Author/Editor Response
The authors reply:
To the Editor: The compression-of-morbidity hypothesis says that, in modern populations with relatively low mortality rates, the effects of preventive measures will be greater on age-adjusted disability (morbidity) than on age-adjusted mortality, leading to decreased cumulative lifetime disability (morbidity), as is recognized by Harper and Forbes. In our report,1 we found that disability in low-risk groups was delayed by more than five years, that cumulative disability decreased through the age of 75, and that disability in the year before death was markedly reduced as compared with that in the high-risk groups. Since the years of greatest mortality and disability in our study population still lie ahead, our data strongly support but do not prove the hypothesis.
The additional life expectancy beyond the age of 75 is approximately nine years in men.2 In our data, the cumulative disability at an average age of 75 is 0.92 unit for persons at high risk and 0.45 unit for those at low risk, with roughly linear but slowly accelerating trends toward greater disability. Assuming a doubling of current disability rates of 0.28 and 0.14 per year over the next nine years, the cumulative disability at the age of 84 would become approximately 3.8 units in the high-risk group and 2.1 units in the low-risk group. For the low-risk persons to reach an average of 3.8 disability units, they would have to live, on average, more than five years longer than the high-risk persons.
The mortality differences between groups are projected to be not nearly that great. Major differences in physical-activity levels suggest approximately a two-year increase in longevity.3,4 The high-risk population in the Multiple Risk Factor Intervention Trial at 10.5 years showed a reduction in mortality rate of 7.7 percent, translating into an increase in longevity of less than 1 year for those with reduced blood pressure, lower cholesterol, and less cigarette smoking.5 By the age of 85, differences in mortality rates between low-risk and high-risk groups narrow greatly. For example, the life expectancy for women is only 1.2 years more than that for men, and the difference between African-American men and white men is only 0.1 year.2
Our studies are longitudinal and ongoing and should permit disease-specific inquiries in the future. The increasing role of competing mortality risks as people age is expected to shorten the course of many chronic illnesses that begin late in life.
5 ReferencesJames F. Fries, M.D.
Helen Hubert, M.D., Ph.D.
Anthony J. Vita, M.D.
Stanford University School of Medicine, Palo Alto, CA 94304-18081
Vita AJ ,Terry RB ,Hubert HB ,Fries JF . Aging, health risks, and cumulative disability. N Engl J Med 1998;338:1035-1041
Full Text | Web of Science | Medline2
Kranczer S . Record high U.S. life expectancy. Stat Bull Metrop Insur Co 1997;78:2-8
Medline3
Paffenbarger RS Jr ,Hyde RT ,Wing AL ,Lee I-M ,Jung DL ,Kampert JB . The association of changes in physical-activity level and other lifestyle characteristics with mortality among men. N Engl J Med 1993;328:538-545
Full Text | Web of Science | Medline4
Kushi LH ,Fee RM ,Folsom AR ,Mink PJ ,Anderson KE ,Sollers TA . Physical activity and mortality in postmenopausal women. JAMA 1997;277:1287-1292
CrossRef | Web of Science | Medline5
The Multiple Risk Factor Intervention Trial Research Group (MRFIT)
CrossRef | Web of Science
Author/Editor Response
Dr. Campion replies:
The compression-of-morbidity hypothesis has been difficult to study, because a cohort must be followed for so long before one can draw firm conclusions. Nonetheless, the trends to date detailed by Vita et al. do support this hypothesis. The data from this study cohort should be much clearer by the year 2010, even though a few of the subjects should still be alive and in their 10th decades.
Edward W. Campion, M.D.
- Citing Articles (3)
Citing Articles
1
J. M. Guralnik, L. Alecxih, L. G. Branch, J. M. Wiener. (2002) Medical and Long-Term Care Costs When Older Persons Become More Dependent. American Journal of Public Health 92:8, 1244-1245
CrossRef2
René Guéguen. (2002) Proposition of an Aging Indicator from General Health Examination in France. Clinical Chemistry and Laboratory Medicine 40:3, 235-239
CrossRef3
Susanne Rasoul-Rockenschaub, M. Bodingbauer, F. Muhlbacher. (2001) Der geriatrische Patient aus chirurgischer Sicht - Internistische Evaluierung, Vorbereitung und postoperative Betreuung. European Surgery-Acta Chirurgica Austriaca 33:5, 214-217
CrossRef
