Your birthday could affect when you die, study says
Does the sun really have an influence on human lifespan and reproduction? If the possibility sounds like some pseudo-scientific astrological nonsense, listen up, because biologists in Norway are proposing that exposure to the sun rays can reduce your lifespan up to 5 years, and if you're female, make it less likely that you yourself will reproduce.
The study, published in "Proceedings of the Royal Society B" relied on historical data found in records from 1676 and 1878 so we can be relatively sure that the people studied spent most of their time localized to Norway and experienced the same solar conditions.
In a survey of the birth and death records of 8,662 people over the two hundred year period the researchers chose to sample, the data showed a reduced life expectancy of up to 5.2 years in people born during years of increased solar radiation. Worse, women of the low socio-economic classes born during those times, were likely to experience reduced fertility and low lifetime reproductive success. When solar activity is relatively calm at your birth, then you were likely to live longer.
See the graph below to see when sola spots occurred (and therefore heightened solar activity), and check out this chart to see where your birthday lands.
So what does this mean? Why would the solar cycle, an ~11 year cycle of the sun's magnetic activity, have any influence on some human on earth's ability to reproduce? The answer may lie in UV radiation.
Of all the types of radiation emitted from the sun, it seems like UV radiation has the worst reputation. We know that UV radiation causes skin cancer and contributes to premature aging and DNA damage. But the authors of the Norwegian study attribute the deadly effects of UV rays to a molecular mechanism. Specifically, its destruction of folate.
Folate or Folic acid is a crucial biological molecule that helps out in many of the reactions that keep our bodies going. It is also necessary for cellular division because of its role in DNA synthesis and repair, but exposure to UV radiation can destroy this crucial nutrient and have physiological consequences.
It is known that a deficiency in folate leads to complications in pregnancy and development, but unfortunately for us, we can't synthesize it ourselves, we've got to eat it. Most pregnant women are encouraged to take folate supplements to promote proper fetal development, but it's an easy bet that those Norwegians back in 1679 weren't able to pop a supplement when they found out they were pregnant. Today's scientists think that low folate levels may be the reason for the low birth rates and reduced life expectancy of people born during periods of high UV exposure.
There are so many other variables that can influence lifespan and reproductive success -- like diet, and workload -- in addition to environmental factors like the sun, that at best this should be taken as a study of correlation, NOT causation. Still, it is interesting to think about how phenomena we take for granted every day -- like the sun rising -- may be having unknown consequences on the very paths of our lives.
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