Genetics of Human Longevity: New Ideas and Findings Dr. Natalia S. Gavrilova, Ph.D. Center on Aging, NORC and the University of Chicago, Chicago, Illinois, USA
Three scientific problems: • Mechanisms of familial transmission of human longevity Paradox of low heritability of lifespan vs high familial clustering of longevity • Parental-age effects (accumulation of mutation load in parental germ cells) Does progeny conceived to older parents live shorter lives? • Does exceptional human longevity come with high cost of infertility? Testing the evolutionary theories of aging
“The Heritability of Life-Spans Is Small”C.E. Finch, R.E. Tanzi, Science, 1997, p.407 Paradox of low heritability of lifespan vs high familial clustering of longevity “… long life runs in families” A. Cournil, T.B.L. Kirkwood, Trends in Genetics, 2001, p.233
Early Study on Familial Longevity • This study found that the relatives of nonagenarians and centenarians live longer than relatives of shorter-lived individuals • These findings were confirmed in later studies (Gudmundsson et al., 2000; Perls et al., 2002 and others )
Characteristic of our Dataset • Over 16,000 persons belonging to the European aristocracy • 1800-1880 extinct birth cohorts • Adult persons aged 30+ • Data extracted from the professional genealogical data sources including Genealogisches Handbook des Adels, Almanac de Gotha, Burke Peerage and Baronetage.
Daughter's Lifespan(Mean Deviation from Cohort Life Expectancy)as a Function of Paternal Lifespan • Offspring data for adult lifespan (30+ years) are smoothed by 5-year running average. • Extinct birth cohorts (born in 1800-1880) • European aristocratic families. 6,443 cases
Unusual Non-linear Pattern of Lifespan Inheritance It is theoretically predicted (by quantitative genetics) and experimentally confirmed that the dependence of most offspring quantitative traits (body weight for example) on parental traits is linear. However, if some parents are damaged during early development and therefore have shorter lifespan (despite having normal germ cell DNA), the dependence for lifespan inheritance should become non-linear. This is because the offspring born to these short-lived parents with normal germ cell DNA should have normal rather than shorter lifespan
Offspring Lifespan at Age 30 as a Function of Paternal LifespanData are adjusted for other predictor variables Daughters, 8,284 cases Sons, 8,322 cases
Offspring Lifespan at Age 60 as a Function of Paternal LifespanData are adjusted for other predictor variables Daughters, 6,517 cases Sons, 5,419 cases
Offspring Lifespan at Age 30 as a Function of Maternal LifespanData are adjusted for other predictor variables Daughters, 8,284 cases Sons, 8,322 cases
Offspring Lifespan at Age 60 as a Function of Maternal LifespanData are adjusted for other predictor variables Daughters, 6,517 cases Sons, 5,419 cases
Person’s Lifespan as a Function of Spouse LifespanData are adjusted for other predictor variables Married Women, 4,530 cases Married Men, 5,102 cases
Person’s Lifespan as a Function of Sisters LifespanData are adjusted for other predictor variables Females, 5,421 cases Males, 7,378 cases
Person’s Lifespan as a Function of Sisters-In-Law LifespanData are adjusted for other predictor variables Females, 4,789 cases Males, 4,707 cases
Mortality KineticsLong-Lived Mutants of Mouse and Drosophila Mouse Snell dwarf mutant. Flurkey et al., PNAS, 2001. Drosophila mutant methuselah. Lin et al., Science, 1998.
Mortality Kinetics for Progeny Born to Long-Lived (80+) vs Short-Lived ParentsData are adjusted for historical changes in lifespan Sons Daughters
Parental-Age Effects(accumulation of mutation load in parental germ cells) Does progeny conceived to older parents live shorter lives?
Daughters' Lifespan (30+) as aFunctionof Paternal Age at Daughter's Birth6,032 daughters from European aristocratic familiesborn in 1800-1880 • Life expectancy of adult women (30+) as a function of father's age when these women were born (expressed as a difference from the reference level for those born to fathers of 40-44 years). • The data are point estimates (with standard errors) of the differential intercept coefficients adjusted for other explanatory variables using multiple regression with nominal variables. • Daughters of parents who survived to 50 years.
Paternal Age as a Risk Factor for Alzheimer Disease • MGAD - major gene for Alzheimer Disease • Source: L. Bertram et al. Neurogenetics, 1998, 1: 277-280.
Paternal Age and Risk of Schizophrenia • Estimated cumulative incidence and percentage of offspring estimated to have an onset of schizophrenia by age 34 years, for categories of paternal age. The numbers above the bars show the proportion of offspring who were estimated to have an onset of schizophrenia by 34 years of age. • Source: Malaspina et al., Arch Gen Psychiatry.2001.
Is There Any Link Between Longevity and Fertility? What are the data and the predictions of the evolutionary theory on this issue?
Brief Historical Note • Beeton, M., Yule, G.U., Pearson, K. 1900. Data for the problem of evolution in man. V. On the correlation between duration of life and the number of offspring. Proc. R. Soc. London, 67: 159-179. • Data used: English Quaker records and Whitney Family of Connectucut records for females and American Whitney family and Burke’s ‘Landed Gentry’ for males.
Findings and Conclusions by Beeton et al., 1900 • They tested predictions of the Darwinian evolutionary theory that the fittest individuals should leave more offspring. • Findings: Slightly positive relationship between postreproductive lifespan (50+) of both mothers and fathers and the number of offspring. • Conclusion: “fertility is correlated with longevity even after the fecund period is passed” and “selective mortality reduces the numbers of the offspring of the less fit relatively to the fitter.”
Other Studies, Which Found Positive Correlation Between Reproduction and Postreproductive Longevity • Alexander Graham Bell (1918): “The longer lived parents were the most fertile.” • Bettie Freeman (1935): Weak positive correlations between the duration of postreproductive life in women and the number of offspring borne. Human Biology, 7: 392-418. • Bideau A. (1986): Duration of life in women after age 45 was longer for those women who borne 12 or more children. Population 41: 59-72.
Studies that Found no Relationship Between Postreproductive Longevity and Reproduction • Henry L. 1956. Travaux et Documents. • Gauter, E. and Henry L. 1958. Travaux et Documents, 26. • Knodel, J. 1988. Demographic Behavior in the Past. • Le Bourg et al., 1993. Experimental Gerontology, 28: 217-232.
Study that Found a Trade-Off Between Reproductive Success and Postreproductive Longevity • Westendorp RGJ, Kirkwood TBL. 1998. Human longevity at the cost of reproductive success. Nature 396: 743-746. • Extensive media coverage including BBC and over 70 citations in scientific literature as an established scientific fact. Previous studies were not quoted and discussed in this article.
Number of progeny and age at first childbirth dependent on the age at death of married aristocratic women Source: Westendorp, R. G. J., Kirkwood, T. B. L. Human longevity at the cost of reproductive success. Nature, 1998, 396, pp 743-746
Do longevous women have impaired fertility ?Why is this question so important and interesting: • Scientific Significance. This is a testable prediction of some evolutionary theories of aging (disposable soma theory of aging, Westendorp, Kirkwood, 1998) • Practical Importance. Do we really wish to live a long life at the cost of infertility? Based these concerns a suggestion was made: "... increasing longevity through genetic manipulation of the mechanisms of aging raises deep biological and moral questions. These questions should give us pause before we embark on the enterprise of extending our lives“ Walter Glennon "Extending the Human Life Span", Journal of Medicine and Philosophy, 2002, Vol. 27, No. 3, pp. 339-354 • Educational Significance. Do we teach our students right? Impaired fertility of longevous women is often presented in scientific literature and mass media as already established fact (Kirkwood, 2002; Westendorp, 2002; Glennon, 2002; Perls et al., 2002 etc.) Is it a fact or artifact ?
Point estimates of progeny number for married aristocratic women from different birth cohorts as a function of age at death.The estimates of progeny number are adjusted for trends over calendar time using multiple regression. Source: Westendorp, R. G. J., Kirkwood, T. B. L. Human longevity at the cost of reproductive success. Nature, 1998, 396, pp 743-746
General Methodological Principle: • Before making strong conclusions, consider all other possible explanations, including potential flaws in data quality and analysis • Previous analysis by Westendorp and Kirkwood was made on the assumption of data completeness:Number of children born = Number of children recorded • Potential concerns: data incompleteness, under-reporting of short-lived children, women (because of patrilineal structure of genealogical records), persons who did not marry or did not have children.Number of children born >> Number of children recorded
Test for Data Completeness Direct Test: Cross-checking of the initial dataset with other data sources We examined 335 claims of childlessness in the dataset used by Westendorp and Kirkwood. When we cross-checked these claims with other professional sources of data, we found that at least 107 allegedly childless women (32%) did have children! At least 32% of childlessness claims proved to be wrong ("false negative claims") ! Some illustrative examples: Henrietta Kerr (16531741) was apparently childless in the dataset used by Westendorp and Kirkwood and lived 88 years. Our cross-checking revealed that she did have at least one child, Sir William Scott (2nd Baronet of Thirlstane, died on October 8, 1725). Charlotte Primrose (17761864) was also considered childless in the initial dataset and lived 88 years. Our cross-checking of the data revealed that in fact she had as many as five children: Charlotte (18031886), Henry (18061889), Charles (18071882), Arabella (1809-1884), and William (18151881). Wilhelmina Louisevon Anhalt-Bernburg (17991882), apparently childless, lived 83 years. In reality, however, she had at least two children, Alexander (18201896) and Georg (18261902).
Antoinette de Bourbon(1493-1583) Lived almost 90 years She was claimed to have only one child in the dataset used by Westendorp and Kirkwood: Marie (1515-1560), who became a mother of famous Queen of Scotland, Mary Stuart. Our data cross-checking revealed that in fact Antoinette had 12 children! • Marie 1515-1560 • Francois Ier 1519-1563 • Louise 1521-1542 • Renee 1522-1602 • Charles 1524-1574 • Claude 1526-1573 • Louis 1527-1579 • Philippe 1529-1529 • Pierre 1529 • Antoinette 1531-1561 • Francois 1534-1563 • Rene 1536-1566
Characteristics of Our Data Sample for ‘Reproduction-Longevity’ Studies • 3,723 married women born in 1500-1875 and belonging to the upper European nobility. • Women with two or more marriages (5%) were excluded from the analysis in order to facilitate the interpretation of results (continuity of exposure to childbearing). • Every case of childlessness has been checked using at least two different genealogical sources.
Acknowledgments This study was made possible thanks to: generous support from the National Institute on Aging, and stimulating working environment at the Center on Aging, NORC/University of Chicago
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