The researchers behind the study, published in Proceedings of the Royal Society B today, analysed births and deaths in 2 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 5 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 radiation people on earth are exposed to can increase. This increased ultraviolet radiation could have damaging consequences on health and longevity.
"Ultraviolet radiation can suppress essential molecular and cellular mechanisms during early development", say the authors of the study. "Variations in solar activity during early development may thus influence their health and reproduction."
The team say the detrimental effects of high ultraviolet radiation during development are unclear but that high levels of ultraviolet radiation might cause degradation of vitamin B which is needed for healthy gestation, DNA damage and membrane damage in developing foetuses.
The team analysed data from church records of more than 8,500 people born in Norway between 1676 and 1878. Of all the children, around 20% died before they reached 20. 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.