A new study shows that periods of high UV radiation
can affect a population over several generations.
Gine Roll Skjærvø at NTNU’s Department of Biology
has studied church records from the period 1750-1900
and looked at life history variables: how old were
women when they had their first child, and their
last? How many years passed between the birth of
each child, and how many of these children survived?
How many of these children were in turn married and
had children?
Robert A. Rohde/GNU General Public License
All told, she studied information from more than
9,000 people listed in the church records she
examined.
Part of this information was compared with
environmental factors, including solar activity.
Skjærvø and her colleagues found that children born
in the years with lots of solar activity had a
higher probability of dying compared to children who
were born in the years with less solar activity.
On average, the lifespan of children born in years
that had a great deal of solar activity was 5.2
years shorter than other children. The largest
difference was in the probability of dying during
the first two years of life.
Children who were born in years with lots of
sunshine and who survived were also more likely to
have fewer children, who in turn gave birth to fewer
children than others. This finding shows that
increased UV radiation during years of high solar
activity had an effect across generations.
Skjærvø used information on the number of sunspots
as an indication of the amount of UV radiation in a
given year. The number of sunspots reaches a maximum
every 11 years on average, which results in more UV
radiation on Earth during years with high sunspot
and solar activity.
UV radiation can have positive effects on human
vitamin D levels, but it can also result in a
reduction of vitamin B9 (folate). It is known that
low folate levels during pregnancy are linked to
higher child mortality.
The NTNU study showed that families from the lowest
socio-economic groups were most affected by UV
radiation. This is probably related to the time
period Skjærvø studied, which was a time of clear
class distinctions in Norway, especially in rural
areas. Women who worked in the fields were more
exposed to the sun than other women. In many cases
they also had a poorer diet.
Both climate change and variability in the ozone
layer are expected to increase the amount of UV
radiation reaching the Earth in the future. At the
same time, there have been many societal changes
since the 1900s.
Nevertheless the NTNU researchers felt it prudent to
caution women who want to have children.
“There are probably many factors that come into
play, but we have measured a long-term effect over
generations.
The conclusion of our study is that you should not
sunbathe if you are pregnant and want to have a lot
of grandchildren,” says Skjærvø.
Scientists are particularly concerned about people
with light skin who move to warmer climates with
lots of sun.
For more information
7 January issue of the Proceedings of the Royal
Society B and is entitled:
“Solar
activity at birth predicted infant survival and
women’s fertility in historical Norway.”
MDN |