Sperm Age as Ova Do: Risks Offset by Benefits?
Since more and more people are having kids later in life, study after study has said that women who bear children after 30 have greater and greater risk of passing chromosomal damage to their fetuses as their ova begin to break down. Little has been said about the impact of older DNA from men, though. New studies are coming out now showing that the male contribution may have an expiration date on it as well. In effect, these studies show that sperm age as ova do…but they also show some benefits of waiting that might outweigh the risks.
People in developed countries have been having children later and later. Some parents cite careers and financial stability factors as reasons for later child-rearing, stating that they want to be settled into a good home and marriage before raising children. Others have said that they feel more emotionally and mentally mature and thus more able to raise children with less negative psychological impacts and with better communication skills after 30.
Risks for late childbearing for women are known to society as a whole, of course. Women are told as they pass 29 years that the risks start to mount every year, multiplying after 35 and still more after 40, and include the possibility of Down Syndrome, miscarriage, stillbirth and ectopic pregnancies, Autism and a variety of chromosomal and genetic defects that seem less likely to stay “switched off” the more ova age.
Recent scholarship suggests that older men can contribute to this problem as well, however, so that the longer both parents wait to have children, the more the risks to the child’s health.
The new evidence shows that where many older women risk chromosomal damage from the DNA in their ova, older men are more likely to contribute to psychiatric conditions and disorders in their children, including a greater likelihood by three times of producing a child with a disorder on the autism spectrum. There was also evidence of a much higher likelihood of ADHD and Bipolar disorders in the children of older men, at 13 times and 25 times more likely respectively. They found a two-times-greater risk of psychotic disorders, as well as a higher likelihood of schizophrenia. The current theory is that mutated sperm are the culprits in this finding.
Unlike ova, which are formed in women while they are fetuses themselves and age along with women in a finite supply, men produce new sperm constantly. Thus scientists had thought that older men came with fewer risks for child-rearing than do older women. This study suggests that though sperm themselves do not age the way ova do, the mechanisms which generate sperm age along with men’s bodies, thus making it more likely that men will produce faulty sperm with more mutations, or error codes, as they age.
These mutations are likely to be the reason for the findings. The study was conducted via the Karolinska Institute in Sweden, by comparing the children of men who became fathers after age 45 to the children of men who became fathers between 20 and 24. There were 2,600,000 children in the study; a vast and comprehensive data pool by the standards of the scientific method. Scientists peer-reviewing the results found the study to be well-designed in that it also compared siblings with the same father raised in different households.
The inclusion of upbringing as a variable is important in a study like this because environment can also have an effect on mental health. Good control group comparisons are essential in such a study, since findings included a higher likelihood of lower test scores, substance abuse issues and suicidal behavior from the children of men who had waited till after age 45 to become fathers. They found the latter two issues to be two-and-a-half times more likely in this group than in the group with fathers in their twenties, indicating a need to make broader comparisons to rule out social programming or other environmental factors.
Though the study compared fathers older than 45 with much younger fathers, the researchers point out that there is no sudden onset of problems at a particular age. Rather, they say, risk of psychiatric disorders simply becomes higher with age, as is the case with women. The scientists were also quick to point out that these are still low risk numbers in that doubling the risk of a disorder that is already rare means the disorder is still rare. Their concern is that as this trend increases in societies as a whole and the children of these older parents begin to pair up and have children themselves, these risks might become less and less recessive with successive generations.
So sperm, or rather the mechanism that makes them, ages, making older sperm as risky as do older ova; but are there benefits to offset the risks?
Scientists have said that older fathers should not panic at these findings at this time, since these disorders continue to be less likely than the likelihood of having a healthy child. As well, whatever their DNA latencies, older adults in stable relationships and with stable jobs and incomes are indeed more likely to raise healthy children, so there is a great deal of give and take in the equation.
Besides the stability factor, other benefits of late child-rearing might contribute to outweigh the risks. Previous studies have shown that older fathers might actually confer unique survival advantages to their children along with any potential for disorders. Last year Dr. Dan Eisenberg of Northwestern University and his team showed that older fathers, as well as their fathers in turn, may in fact reprogram their sperm as they age so that they will in turn pass on the genetics for longevity.
Sperm DNA changes over the course of a man’s life, adopting positive mutations which might code for longer life spans. This second study, performed in the Philippines, analyzed 1,779 adults and found that structures known as telomeres grow longer in sperm as men age. These formations, which are situated at the ends of chromosomes, actually protect the areas that carry genetic codes. Scientists have likened telomeres to the little plastic bits that adorn the ends of shoelaces to keep them from fraying. Telomeres in effect coat the ends of chromosomes to shield them from damage.
In most chromosomes throughout the body, telomeres wear out and shorten with age, allowing DNA to sustain more and more hits from a long life. In sperm, however, this study found that telomeres actually get longer as men age. The DNA being damaged from lack of long telomeres is not the DNA men pass on to their children. Instead they pass on the DNA from sperm; DNA protected by those abnormally long and ever-growing telomeres. The length of telomere from one generation is passed down as is to the next to become the average length of all the telomeres in the next generation’s body. That child may in turn build on the length of his telomeres by waiting to have children until his already long telomeres are lengthened in his sperm, thus adding even more longevity to the family tree.
In effect it was found that men with shorter telomeres appear to code for shorter life spans in their children, while men with longer telomeres seem to code for longer life spans. Thus a grandfather who had children at an older age would pass his longevity to a father, who would, if he had children at a later age, in turn pass longer telomeres again to his children.
The effects of longer telomeres could include not just protection of one’s DNA, but could also help that DNA—and therefore the structures for which DNA codes, e.g. cells—to regenerate by coding for quicker growth and cell replacement. This could lead to better immune systems, digestions, skin production and healing.
So though both men and women have been shown to have a biological clock with regard to reproduction, the risks of having children at a later age might also come with unexpected benefits; benefits that, like the risks, can be passed on and increased from generation to generation. Sperm may, in effect, age as ova do, but they also pass on amazing benefits which, like a stable job and relationship, emotional maturity and a better income, can offset the risks of waiting to become a parent.
By Kat Turner