Fertility In Older Age Associated With Longer Life

By Margarita Nahapetyan

Women who naturally give birth to a baby in their older years, tend to live a longer life compared to women who have babies in their 20s and 30s, claims a new study by the University of Utah scientists.

The study showed that not only women who have children in their 40s or 50s have a better chance to live longer than other women, but their brothers also live longer. This could only suggest that the same genes prolong lifespan and female fertility, and may play a bigger role and be more important than social and environmental factors. The team of experts from the U. of U., University of Western Ontario, and the University of Montreal also focused on the wives of the brothers in order to determine if the longevity could be associated with environmental conditions, such as food, shelter and disease. But the wives, who were not blood relatives, did not appear to lead longer lives.

If women in your family give birth to a child at an older age, you may have a good chance to live longer than you would otherwise, says the study's lead researcher, demographer Ken R. Smith, a professor of family and consumer studies at the University of Utah. "If you have a female relative who had children after age 45, then there may be some genetic benefit in your family that will enhance your longevity," he added.

For the study purposes, the investigators analyzed high-quality genealogical records from the Utah Population Database at the University of Utah with its data of more than 1.5 million Utah Mormon pioneers and their descendants. The experts also used the University of Montreal's Program on Demographic History Research, which has data on 400,000 people who lived in heavily Catholic Quebec between 1608 and 1850. To be more specific, the research used the records of 11,604 Utah men who were born between 1800 and 1869 and who had at least one sister who lived at least to the age of 50 years. The experts also used the information on 6,206 Quebec men who lived between 1670 and 1750, with at least one sister who lived to 50 years of age or older. They found that:

• Women with fertility at an older age - a birth at the age of 45 or older - were 14 per cent to 17 per cent less likely to die during any year after the age of 50 compared to women who delivered a child at an earlier age. These findings coincide with the results of some previous studies. However, those studies failed to determine whether the women who gave birth later lived a longer life because of genetic factors or because of social and environmental factors such as healthy diet or healthy living.

• Brothers who had at least three sisters, among whom at least one sister gave birth at the age of 45 years or older, were 20 per cent to 22 per cent less likely to die during any year after the age of 50 years, compared to brothers who had no sisters with late fertility. This shows that the same genes may affect the lifespan of both genders and women's ability to give birth at older ages.

• The wives of these brothers did not live longer lives, which indicates that any environmental or social factors that influence lifespan had only a weak influence, and that genes may be a factor why brothers lived longer when they had a sister who gave birth in her 40s or 50s.

The study did not specify how much longevity is due to genetics, but the investigators believe that genes account for up to 25 per cent of differences in leaving a longer life.

The findings were published online May 4 and will also appear in the June 10 print issue of the Journal of Gerontology: Biological Sciences.