Who Are Centenarians? (continued pg. 3)

If such clustering of extremely old siblings does not occur by chance, but rather it occurs because of common genetic and/or environmental factors, then encountering such families would be much more probable than recently believed.

If extreme old age does run in families, as suggested by these findings, such families may be more common than previously thought. Further delineation of other similar families and perhaps searching for discrete genes and environmental factors that may be common among them may yield important determinants of extreme longevity.

Older Mothers Live Longer (Reference 11, Below)
The most reliable predictor we have of when a woman will go through menopause is the age at which her mother went through it. As of yet, we don't know what genetic or environmental factors mothers and daughters have in common to determine this association, but these same factors may also influence rates of aging and susceptibility to diseases associated with aging.

As we reviewed the pedigrees of a number of our centenarian subjects living in the suburban Boston area, we came across a substantial number of women who had children in their forties. There was even one that had a child at the age of 53 years. This struck us as unusual given that maternal age greater than forty is a relatively rare event. Less than 3 percent of births occur in women 40 years of age or older. In 1995 the birth rate of American women 40-44 years was 6.6 per 1000 women, and 0.3/1000 for women 45-49. However, a history of older maternal age among our centenarian subjects made sense to us since aging relatively slowly is a likely necessary characteristic of achieving extreme age and women who do so, should be able to bear children at an older age.

We went on to compare 78 female centenarians with a similar birth cohort of fifty-four women born in 1896, but who died at of the age of 73 years in 1969. By collecting data on a similar birth cohort, we were able to minimize concerns about temporally related influences upon fertility such as health and contraception-related trends. We found that 19.2% of the centenarians had children at age 40 years or older compared to 5.5% of the women who lived to age 73.

We concluded that if you are a woman who naturally had a child in her forties, you are four times more likely to live to 100 years old rather than dying at the age of 73. However, we believe that it is not the act of having a child in your forties that promotes long life, but rather that having a child late in life is an indicator that the woman's reproductive system is aging slowly. A slow rate of aging would therefore bode well for the woman's subsequent ability to achieve very old age.

What are the factors that link the slowly aging reproductive system and the ability to reach extreme age? Ideally, to identify the reproductive factors which are associated with longevity we would like to know the status of various reproductive factors such as age at menarche, cycle regularity, number of spontaneous abortions and age of menopause. Unfortunately, obtaining this type of information from relatives of the deceased is difficult and unreliable. During the first quarter of this century, fertility enhancing interventions for older women were not available. Under these circumstances, knowing when a woman last had a child is our best estimate of her premenopausal status and therefore reflects her natural ability to have conceived later in life. Relatively delayed menopause, like pregnancy after age 40, may be a marker for aging slowly and the subsequent ability to achieve extreme longevity. This finding is interesting not only for its potential value in predicting individuals predisposed to extreme longevity, but also because it has implications regarding the theoretical basis of menopause and human life span.

Centenarians continued

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