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How old a man is when he has children may affect the lifespans of his grandchildren, a new study suggests.
Men in the study who were older when they had children tended to have kids and grandkids with longer telomeres — caps on the ends of chromosomes that protect the chromosomes from damage.
People with longer telomeres have been found to have a decreased risk of dying over a given time period, compared with people with shorter telomeres, and longer telomeres are thought to protect against aging, the researchers said.
In most cells, telomeres get shorter with age, but in sperm cells, they get longer, the researchers said. When men delay having children, those longer telomeres of their sperm cells may be passed on to the next generation. Moreover, the effect appears to be additive across generations, the researchers said.
The findings suggest that being born into a lineage in which the males reproduced at later ages has health benefits, said study researcher Dan Eisenberg, a doctoral researcher in anthropology at Northwestern University.
However, the researchers noted that an older age of fatherhood also brings risks for the children — studies have shown that older fathers may be at more likely to pass down certain genetic mutations, which may increase the risk of miscarriage or certain diseases. Studies have also found children of older fathers are more likely to be diagnosed with neurological conditions such as autism. [See: Best Age to Have Kids.]
Studying telomere length
In the new study, Eisenberg and colleagues analyzed DNA from the blood of 1,779 young adults (ages 21 to 23) in the Philippines and their mothers (ages 36 to 69), and determined the ages of their fathers and grandfathers at the time the children were born.
Results showed that for each year a man delayed having children, the length of the telomeres of his children increased, and this effect was additive over generations.
The findings held even after the researchers took into account factors that could affect telomere length, such as the children's birth order, body mass index, household income and age at which the blood samples were taken.
The yearly increase in telomere length seen in sperm cells was about equal to the amount of telomere length lost in normal aging, Eisenberg said.
Earlier work has shown children of older fathers tend to have longer telomeres, but researchers had not looked to see if this effect is cumulative across generations.
The findings suggest that telomere length is one way that parents "send signals" to their offspring about the environment they will be born into, Eisenberg said.
"If your father and grandfather were able to live and reproduce at a later age, this might predict that you yourself live in an environment that is somewhat similar — an environment with less accidental deaths or in which men are only able to find a partner at later ages," Eisenberg said. "In such an environment, investing more in a body capable of reaching these late ages could be an adaptive strategy from an evolutionary perspective," he said.
Telomere length likely has the biggest effect on cells in the body that divide a lot during life, Eisenberg said, such as cells of the skin, gut lining and immune system. Some studies show people with shorter telomere length are more likely to die of infectious diseases and cardiovascular disease, Eisenberg said.
However, more research will be needed to show whether those with longer telomeres in the current study actually suffer from fewer health problems, the researchers said.
The study will be published this week in the journal Proceedings of the National Academy of Sciences.
Pass it on: Being born into a family in which the father and grandfather had children at older ages may increase your telomere length — and your lifespan.