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Longevity

Older fathers and grandfathers may have longer living children

You may crack jokes about your ‘old man’s’ age, but it actually may be benefitting you in the long run.

New research from Northwestern University has found that the longer fathers and grandfathers waited to have children, the more likely it was for their offspring to live longer and healthier lives.  

The study, published in the Proceedings of the National Academy of Science, seemingly stands in contrast to previous research that maintains having children younger is better for the health of the child.  Known as the paternal age effect, numerous studies have suggested that the older a man is when he reproduces, the increased likelihood that his children will develop birth defects or health-related disorders.

But according to Dan Eisenberg, a doctoral candidate in anthropology at Northwestern as well as the study’s lead author, the findings of their research don’t necessarily stand at odds with this previous research.  

“I don’t think this contradicts those other findings, and we don’t recommend people have kids at a later age,” Eisenberg told FoxNews.com.  “But one major point is that what seems to be occurring is kind of interrelated with why children of older men have these mutations.”

The answer lies in a person’s telomeres – DNA found at the end of chromosomes, offering protection as cells continuously divide throughout a person’s life.  Each time a cell divides, telomeres grow shorter and shorter.  Because of their slow decay, longer telomeres are often associated with slower aging while shorter telomeres usually are behind ill health that comes with growing older.

After conducting a longitudinal study of over 1,700 young adults in the Philippines over a 30 year period, Eisenberg and his team found that children of older fathers inherit longer telomeres and even more interestingly enough – this inheritance held true across multiple generations.  

Eisenberg said that the explanation could lie in every day sperm production.

“Men produce about 100 million sperm per day, while women produce all their eggs in utero and then no more are produced in their lifetime,” Eisenberg said.  “The way telomeres work is that they get a little shorter as the cell has to divide.  But in actuality if we look at sperm in older men, the sperm have longer telomeres.  But in the blood of older men, the cells have short telomeres.”

“We are not certain why telomeres are longer in sperm of older men,” Eisenberg continued, “but the most prominent explanation is that an enzyme called telomerase – which helps to extend the length of telomeres – is active at high levels in the testis. This telomerase activity could progressively extend telomere length as men age. An alternative explanation is that the sperm progenitor (stem cells) which have shorter telomere lengths tend to die out as a man ages.”

According to Eisenberg, the more replications of sperm cells that occur as a man ages, the greater the tendency for mutations to occur – which could lead to the adverse health effects that previous research has found.  So in a sense, Eisenberg’s research compliments past studies on the paternal age effect.

Where the research differs, however, is that Eisenberg’s team didn’t exactly examine fathers who reproduced at significantly older ages.  Instead they mostly compared fathers who differed from each other by a few years.

“In my reading of the literature showing these negative effects is that those tend to examine later ages,” Eisenberg said.  “Those studies tend to report that if you’re over 45 versus 65, there may be bigger effects.  With this telomere story, it’s not just about being an old versus a young father, but with every year, the telomeres get a bit longer.  So if we looked at a 20-year-old father versus a 25-year-old father, the telomere length difference would be the same between a 50 year old father and 55 year old father.”

In order to better understand their findings, the researchers hope to expand beyond just a few generations to see if this effect goes even further back in ancestry.  They also hope to understand what role this inheritance plays in the evolutionary process.

“Is this some sort of adaptive signaling – helping the father to adjust the biology of his child so it’s better to meet demands of the environment?” Eisenberg asked. “That’s our hypothesis, so we might be looking at what are other things aside from age that occur over a father’s lifespan that he gives to his children.”