The children and grandchildren of men who wait until they're 40 to reproduce tend to have longer lives.

Children of older fathers, between late 30's and early-50's, inherit longer telomeres, caps at the end of chromosomes that keep them from degenerating, according to a new study by Dan T. A. Eisenberg at Northwestern University.

The longer telomeres mean that children age more slowly and are likely to live longer. This goes against previous research that said that older fathers were more likely to produce offspring with birth defects.

“Most literature also suggests risks from paternal age and this is intriguing, in part, because it stands in contrast to that,” Eisenberg said in a telephone interview with Bloomberg News. “We don’t really know, on balance, what the net effect is.”

The average American man has his first child at age 25, according to a report from the Centers for Disease Control and Prevention.

Here's a chart showing telomere length and age of father and grandfather: