Why Women Live Longer Than Men

Giora Ram, Ph.D.

Abstract

The fact is that women live longer than men. The reason is a multi-parameter of various factors, some of which arebiological, psychological and social related. This paper is an attempt to bring together some of the factors based on published studies and to suggest new directions for further research, which may explain the longer life spans of women over men.

One of those new directions is in the area of fetal microchimerism, which is the persistence of certainnumbers of fetal cells in the mother after a pregnancy. Another parameter may be found in further studies about the system, which is involved in enhancing mothers’ immune system during and after pregnancy.

Further studies may imply that women who gave birth will live longer than those who didn’t. In addition, those women, who lived to be over 100 years, may have special genes that slow down aging and reduce the probability to have a heart, stroke, cancer or Alzheimer's disease.

The X chromosome may be another influencing factor on female life span. Since women have two X chromosomes, in case one is abnormal, the other may replace it, and in this case she becomes a carrier but without the disease.

Finally, I believe that the longer life span of females might be part of some grand Darwinian scheme and it might alsobe that mother nature is rewarding motherhood.

Facts, Factors and Fiction

The evolutionary force to pass the genes and at the same time the need to stay alive and be able to bear a maximal number of children may be related to the forces of nature that enable women to live longer than men.

Menopause may protect and prolong life for those women who bear children late in life, and may enable them to live longer to take care of them. Researchers [7] studied people who lived longer than 100 years, concluded that menopause is a major determinant of the life spans of both women and men. Few species in addition to human females menstruate in nature. One example is certain types of whales that are mammals.

In the U.S. and other modern countries, the average life expectancy is about 80 years for women and about 70 years for men. In Sweden, for example, during the18th century it was about 37 years for women and 34 for men.

As human life expectancy increased throughout the centuries, it seems that the gap of women life spans over men increased as well.

The probability of women to survive over men during the first 25 years is more than 4 times higher, mainly because of men’s Testosterone. This hormonal factordecreases with the age, but the gap still remains in favor of women. The sex hormones are a factor to consider, young males are aggressive, and haveincreased levels of harmful cholesterol leading to heart disease or stroke. However, the female hormone Estrogen lowers harmful cholesterol and raises "good" cholesterol. Recent studies suggest that estrogen treatment after menopause might reduce the risk of death, especially from heart disease or stroke.

As a rule, females have strong hearts that lastlonger and better blood vesels than males, which couldbe due to the Estrogen hormone. Even with diseases such as: heart disease, stroke, cancer and diabetes, men often die whereas women survive.

This gap of women over men, does not apply to women, who smoke, drink, are overweight or are under excessive stress, which is typical to women who work in domains that were previously male dominant.

There are, however, certain countries where there is almost no such gap, such as India, Pakistan, where there is sexual discrimination and practices such as female infanticide and bride-burning…

Mortality rate may also beaffected by chromosomal differences between men and women. Chromosomescarry genetic mutations that may cause to certain life-threatening diseases. Females have two X chromosomes, so if there is an abnormality in one of them the healthy chromosome replaces it, in this case she becomes a carrier but without the disease. Men have one X and one Y chromosomes, so they cannot use alternative chromosome if a gene on one of them is defective. Such differences in longevity have been observed in nature, in most animals.

Genes of women who lived to be over 100 years should be further researched. I believe that they may have special genes that slow down aging and reduce the probability to have heart, stroke, cancer or Alzheimer's disease.

Another fact is that men are much more likely than women to engage in risky and violent behavior, which leads to an increase in men's death rate. Men also die more than women in car accidents, homicides, and even suicides.

Fetal microchimerism is the persistence of certainnumbers of fetal cells in the mother after a pregnancy. A numberof recent studies [1-5] suggest that it may be the reasonof some autoimmune diseases. However, long-term persistence of fetal cells in healthy women does not indicate that they may cause such diseases. The long-term persistence of fetalcells may also have significance in developmentof tolerance of the fetus.

So if microchimerism may be due to transfer of cells between mother and fetus, further studies might indicate the effect of those fetal cells in enhancing mother’s immune system during and after pregnancy. We know that during pregnancy, cells may migrate between mother and fetus back and forth.

Cell transfer rate from fetus to mother increases as pregnancy progresses. In most cases, the fetal cells are compatible with the mother's immune system, so the mother’s body does not reject them. [6]

Further studies may imply that women who gave birth will live longer than those who didn’t. It might also be that those who gave birth to one male at least will live even longer. The detection of Y-chromosomes or male DNA in women after pregnancy, even in a woman who had her last son manyyears prior toblood sampling, may support this theory.

In general, stem cells may be replicated and are capable of long-term self-renewal. As they do not have any specific structures, they can evolve into specialized cells such as: heart muscle, nerve or blood cells.

The source for blood stem cell transplants comes from bone marrow, peripheral blood and the umbilical cord of newborn babies. A new technology that generated new businesses is the collection and storageof umbilical cord blood stem cells from newborn babies, for future use.

If we accept the usage and advantages of stem cells originated in the umbilical cord in conjunction with the fact that there is transfer of cells between mother and fetus, this may be another factor that may explain and support the theory that women who gave birth will live longer than those who didn’t.

In the Bible [Genesis 16], the English version: “Unto the woman He said: “I will greatly multiply thy sorrow and thy conception ; in sorrow thou shall bring forth children ; and thy desire shall be to thy husband, and he shall rule over thee”…

While in the Hebrew version it is written:” … in sorrow thou shall bring forth Boys”

Although some may claim that “boys” or “banim” is the generic name for “children”, one may wonder if the original aim was as written to Boys…This biblical anecdote appears again in [Tehilim 113:9]: "…As a joyful mother of children", while in Hebrew it is written clearly “boys” (banim).

The question is: ”was it a hint in the Bible that birth of children, especially boys will be remunerated?”, or maybe we can conclude that mother of males has a good reason for joy as boys not only do not bring sorrow but also lengthen their life span?.

Finally, it should be reemphasized that the reason that women live longer is based on multi-parameter of varied factors, some of which were mentioned above. The weight of each factor in contributing to this phenomenon is unknown, however it is obvious that the biological element is playing a major role in determining our lifespan.

Conclusion

I believe that the longer life span of females might be part of some grand Darwinian scheme. So it might be that mother nature is rewarding motherhood and especialy those who gave birth to at least one male, so mothers get a few years (about 5) extra for their effort…and they well deserve it…

References

  1. Bianchi DW, Zickwolf GK, Weil GJ, Sylvester S, DeMaria MA. Male fetal progenitor cells persist in maternal blood for as long as 27 years postpartum. Proc Natl Acad Sci U S A. 1996; 93: 705-708.[Abstract/FreeFullText]

2.Evans PC, Lambert N, Maloney S, Furst DE, Moore JM, Nelson JL. Long-term fetal microchimerism in peripheral blood mononuclear cell subsets in healthy women and women with scleroderma. Blood. 1999; 93: 2033-2037. [Abstract/FreeFullText]

3.Flowers ME, Pepe MS, Longton G, et al. Previous donor pregnancy as a risk factor for acute graft-versus-host disease in patients with aplastic anaemia treated by allogeneic marrow transplantation. Br J Haematol. 1990; 74: 492-496. [Medline][OrderarticleviaInfotrieve]

  1. Lambert NC, Stevens AM, Tylee TS, Erickson TD, Furst DE, Nelson JL. From the simple detection of microchimerism in patients with autoimmune diseases to its implication in pathogenesis. Ann N Y Acad Sci. 2001; 945: 164-171. [Abstract/FreeFullText]
  2. Srivatsa B, Srivatsa S, Johnson KL, Bianchi DW. Maternal cell microchimerism in newborn tissues. J Pediatr. 2003; 142: 31-35. [CrossRef][Medline]

6.Retained Cells from Cell Transfer During Pregnancy: A New Paradigm for Human Health and Disease, Fred Hutchinson Cancer Research Center

7.Why Women Live Longer than Men, Harvard University Gazette, October 1,1998