A new study out of the UK shows that people who have children are more likely to live longer than those who don't.
The study, published in the Scientific Reports journal, says that the increased longevity is due to a "refresh" in the parents' immune systems when children bring home bugs and germs from school.
Authors Miguel Portela and Paul Schweinzer call it the "parental co-immunisation hypothesis".
"[It's] the idea that a parent's immune system is refreshed by a child's infections at a time when their own protection starts wearing thin," they say.
Non-parents - unless they are teachers or nurses, perhaps - do not get the same exposure to infection.
Data for the study was gathered from UK census results of 1971, 1981, 1991, 2001 and 2011.
The pair added that while the impact of lifestyle choices "such as smoking, obesity, drinking and other behavioural factors" had been measured against life expectancy, "the same cannot be said for the individual decision to become a parent."
Their findings echo a similar study conducted in Sweden in 2017, which found that by the age of 60, men with kids had almost two years more on their remaining life expectancy compared to those without. Mothers at the same age could look forward to 1.5 more years alive than those without.
That study named 'social support' as being the significant reason for longer life.