Does Frailty Always Mean Short Longevity?

DOES FRAILY ALWAIS MEAN SHORT LONGEVITY?

A.I Michalski (Institute of Control Sciences RAS, Moscow, Russia),
K.G. Manton (Center for Demographic Studies, Duke University, Durham, NC USA),
A.I. Yashin (Max Plank Institute for Demographic Research, Rostock, Germany)

Purpose
The report is focused on a relationship between individual frailty, disability and longevity. Resent investigation in centenarians give contradictory conclusion about status of health in oldest ages survivors. Hitt, Young-Xu et al. (1999) concluded that centenarians were healthy and independent for most of their lives, but Yashin, Ukraintseva et al. (2001) stated that it would be reasonable to assume that part of the group of centenarians originates from an initially frail part of a generation. In investigations of disability prevalence between men and women in different age groups it was shown that in advanced ages prevalence of disability in women is higher than in men (Andersen-Ranberg, Christensen et al., 1999; Michalski, Manton et al., 2002). Having in mind that women live longer than men this supports that a hypothesis that frailty may be associated with high longevity. This hypothesis corresponds to inverse relationship between initial mortality and parameter of deceleration with age theoretically predicted by Strehler and Mildvan (1960).

Data
Public use analytic data file of four surveys conducted in 1982, 1984, 1989 and 1994 in the frame of National Long Term Care Surveys (NLTCS) was used. The data contain information about disability status of 35848 USA residents (14554 men and 21294 women) born in period 1870-1929 and investigated in 1982, 1984, 1989 and 1994 surveys. The disability in activities of daily living was defined as impossibility to perform without special equipment or personal help at least one of nine activities: eating, getting in/out of bed, getting in/out of chairs, walking around inside, going outside, dressing, bathing, using toilet, urination. Individual life span was defined by difference between year of death and year of birth, provided in analytic data file.

Results
Kaplan-Meier estimates for survival probability among men and women by disability status, observed in 1982, show that men from the age group 90+ in 1982 and reported in 1982 as being unabled to perform only Instrunemtal Activities of Daily Living, had higher chances to survive than those, who was reported as nondisabled. The difference in life expectancy estimates is 2.3 years (p-value < 0.01). Nondisabled women from the same cohort had life expectance higher than women in any group of disability. Mortality estimates demonstrate that people unable to perform Instrumental Activities of Daily Living in the age 65-69 years have higher risk of death than nondisabled people. After age 90 years it becomes opposite in men. In women this change likely takes place in more advanced ages.

Conclusion
New data, obtained in investigations of centenarians and disability in advanced ages, demonstrate inverse relationship between frailty and longevity. The initially frail part of population have higher chances to survive than the initially more robust part. This can be explained in the frame of general theory of mortality and aging, which predicts the inverse relationship between initial mortality and rate of deceleration, related to process of senescence.

References
1. K. Andersen-Ranberg; Christensen, K.; Jeune, B.; Skytthe, A.; Vasegaard, L.; Vaupel, J. W. Declining physical abilities with age: a cross-sectional study of older twins and centenarians in Denmark. Age and Ageing 1999, 28: 373-377.
2. Hitt R, Young-Xu Y, Silver M, Perls T. Centenarians: the older you get, the healthier you have been. Lancet 1999, 354: 652.
3. Manton KG, Corder L, Stallard E. Cronic disability trends in elderly United States populations: 1982-1994. Proc Natl Acad Sci USA 1997, 94: 2593-2598
4. Michalski AI, Manton KG, Yashin AI. Changes Of Disability In Age, Time And Gender. 3rd European Congress of Biogerontolog, Poster. Florence 2002.
5. Strehler BL, Mildvan AS. General Theory of Mortality and Aging. Science 1960, 132: 14-21.
6. Yashin AI, Ukraintseva SV, De Benedictis G, Anisimov VN, Butov AA, Arbeev K, Jdanov DA, Boiko SI, Begun AZ, Bonafe M, Franceschi C. Have the oldest old adults ever been frail in the past? A hypothesis that explains modern trends in survival. J Gerontol A Biol Sci Med Sci 2001, 56: B432-B442.

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