People born when there was low solar activity lived longer on average than those born during times when there was more solar activity, according to a study of births in Norway led by Dr Gine Roll Skjærvø of the Norwegian University of Science and Technology (NTNU) in Trondheim.

Dr Skjærvø and her colleagues, Dr Frode Fossøy and Dr Eivin Røskaft from the NTNU’s Department of Biology, analyzed births and deaths in two parts of Norway between 1676 and 1878.

They compared the lifespan of individuals to the amount of solar activity in the year of the person’s birth.

Their results show that people born in times when the Sun was at its least active lived on average five years longer than those born when the Sun was most active.

The Sun goes through cycles of activity every 11 years, with 8 years of low activity followed by 3 years of high activity.

During peak times when the Sun is most active the amount of ultraviolet (UV) radiation people on Earth are exposed to can increase. This increased UV radiation could have damaging consequences on health and longevity.

“Ultraviolet radiation can suppress essential molecular and cellular mechanisms during early development,” the scientists said.

“Variations in solar activity during early development may thus influence their health and reproduction.”

The scientists, who report their findings in the journal Proceedings of the Royal Society B, said that the detrimental effects of high UV radiation during development are unclear but that high levels of UV radiation might cause degradation of vitamin B (which is needed for healthy gestation), DNA damage and membrane damage in developing fetuses.

In their study, the researchers analyzed data from church records of more than 8,500 people born in Norway between 1676 and 1878.

Those born in years with high solar activity had a lower probability of surviving to adulthood than those born in years with low solar activity.

“On average, the lifespans of individuals born in a solar maximum period were 5.2 years shorter than those born in a solar minimum period,” the scientists wrote in the paper.

“In addition, fertility and lifetime reproductive success were reduced among low-status women born in years with high solar activity.”

“Our results suggest that solar activity at birth may have consequences for human lifetime performance both within and between generations.”

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Gine Roll Skjærvø et al. Solar activity at birth predicted infant survival and women’s fertility in historical Norway. Proceedings of the Royal Society B, published online January 7, 2015; doi: 10.1098/rspb.2014.2032