Most women are aware that their fertility declines more rapidly than other—often more visible—signs of aging. In fact, the ovaries have very unique properties. They begin a prolonged hibernation-like state from infancy until the start of puberty. During this ten to fourteen year period, the ovaries remain inactive; producing neither hormones nor mature eggs. However, there are still biological signs of aging taking place within the resting ovary but at a much slower pace than after the menstrual cycles begin. Then throughout the reproductive years a group of eggs is lost each month. In some women—depending on their diet and lifestyle—eggs may be lost at a faster pace. This happens for instance in women that use tobacco products. As I’ve written about previously, the blood test for the hormone AntiMullerian Hormone (AMH) is considered by most fertility specialists today to be the most reliable assessment of a woman’s ovarian reserve (the approximate number of immature eggs that she has available at any given time). Now there are also new ways to actually measure how we age physiologically as well.
One study recently demonstrated that people do age at variable rates. They quantified the aging process by measuring various physiologic and genetic markers over a 12 year period in 954 individuals beginning at age 26. They correlated their findings with each test subject’s appearance and their quality of life. They found that those that appeared to be aging faster also had measureable changes in their physiology, cognition and physical complaints consistent with their appearance. The researchers also analyzed their DNA. Their analysis supported that some individuals were aging faster than others and that diet and lifestyle seemed to be a major influence on the rate of aging. In fact, some people seemed to age 3 years for each 1 year that passed on the calendar while others didn’t seem to be aging at all during the 12 years of the project. So taking steps to improve your health and wellness may in fact slow your rate of aging. However, there are still some changes taking place that can’t be delayed indefinitely.
In most species, females are able to conceive throughout their natural lifespan. Humans are unique from most other mammals in that women typically live about half of their life after their fertility has ceased. It has also been reported that women that conceive later in life tend to live longer. Efforts to look at the genetic relationship have found that there are 17 genetic markers that explain about 30% of the occurrence of premature ovarian failure. That means that most ovarian aging is related to other factors including damage to the egg’s DNA (telomere length) that naturally occurs over time. There are also changes that occur in the egg’s power house, the mitochondria. Each egg has 20,000 to 800,000 of these important power units. Each mitochondrion has its own small strand of DNA. We inherit all of our mitochondria from our mother. As women age, the DNA of mitochondria within the eggs becomes damaged. This damage cannot be repaired. As a result, the mitochondria are intimately linked to egg quality. They not only impact the chance that an egg will fertilize and grow successfully but also the health of the child that results. There are also other ways that delaying pregnancy may influence the child’s health but in a more positive way. There is considerable evidence that children born to older mothers may have more positive cognitive and behavioral outcomes.
There is a growing trend for women to delay childbearing. Doing so is associated with higher socioeconomic status, increased educational achievement, higher income level and smaller family size. It may be due to any or all of these reasons or it may be due to greater readiness for pregnancy or more that children of older mothers tend to fair better when it comes to cognitive and behavioral measures. Others feel that it may due to a more mature mother-child interaction. Whatever the reason the benefits are present without any elevated risks in psychiatric problems. So even though cause and effect cannot be established in the available studies, advanced maternal age seems to have a protective effect upon the psychological and cognitive development of children. Now there is also evidence that carrying a pregnancy may in turn have healthy implications on the aging of the mother as well.
A new series of investigations is finding that a healthy pregnancy may slow aging process. In animal studies, it has been a consistent finding that pregnancy has a rejuvenating effect upon mother through a process called parabiosis (connecting the circulation between the young and the old). In humans, studies have found measureable benefits including improved liver functioning, improved reparative abilities within the central nervous system and protective effects upon the heart following a healthy pregnancy. There is also data suggesting that unhealthy pregnancies can identify women at risk of age-related conditions like diabetes, stroke and heart disease—possibly identifying those at risk so that preventive measures can be initiated. So it seems that healthy women have a longer opportunity to conceive and that when women in their later years get pregnant that they remain healthier longer.
In summary, the links between fertility and healthy aging are far more complicated than previously believed. We can reassure women that taking steps during their younger years to live a healthy lifestyle should optimize their opportunities for pregnancy. We can not only track a woman’s fertility status through ovarian reserve testing but now we can also freeze/store eggs to extend their reproductive years. Then, by taking steps to optimize a women’s health during pregnancy, women may both have a healthier child as well as slow their own aging.
Enhancing Fertility 