The team overlaid demographic data of Norwegians born between 1676 and 1878 with observations of the Sun.
The lifespan of those born in periods of solar maximum—interludes marked by powerful flares and geomagnetic storms—was "5.2 years shorter" on average than those born during a solar minimum, they found.
"Solar activity at birth decreased the probability of survival to adulthood," thus truncating average lifespan, according to the paper published in the journal Proceedings of the Royal Society B.
There was a stronger effect on girls than boys, it said.
The Sun has cycles that last 11 years, give or take, from one period of greatest activity or solar maximum, to the next.
Solar maxima are marked by an increase in sunspots, solar flares and coronal mass ejections that can disrupt radio communications and electrical power on Earth, damage satellites and disturb navigational equipment.
Solar activity is also linked to levels of ultraviolet radiation— an environmental stressor known to affect survival and reproductive performance, possibly by causing cell and DNA damage, according to the study authors.
[B]On top of lifespan, being born in a solar maximum period also "significantly reduced" fertility for women born into the poor category, but not for wealthier women or for men, said the authors. "We show for the first time that not only infant survival and thus lifespan but also fertility is statistically associated with solar activity at birth," they wrote.
