Rheumatoid arthritis and giant cell arteritis may correlate with solar cycles – unusual new findings
Periodic solar storms may correlate with incidences of rheumatoid arthritis and giant cell arteritis, a group of researchers claim in BMJ Open. The relationship between solar outbursts and the incidence of these diseases could lead to preventive measures if a causal link is established.
Previous research from the Mayo Clinic showed that cases of rheumatoid arthritis and giant cell arteritis followed close to 10-year cycles.
“That got me curious,” Simon Wing explains. “Only a few things in nature have a periodicity of about 10-11 years and the solar cycle is one of them.”
When Simon Wing and colleagues tracked the incidence of rheumatoid arthritis and giant cell arteritis cases compiled by the Mayo Clinic researchers, the results suggested “more than a coincidental connection,” says co-author, Eric Matteson. Increased incidents of rheumatoid arthritis and giant cell arteritis seemed to be in periodic concert with the cycle of magnetic activity of the sun.
The solar cycle
During the solar cycle, dramatic changes that can affect space weather near Earth take place in the sun. At the solar maximum an increased number of outbursts called coronal mass ejections hurl millions of tons of magnetic and electrically charged plasma gas against the Earth’s magnetosphere, the magnetic field that surrounds the planet. This contact whips up geomagnetic disturbances that can disrupt mobile phone service, damage satellites and knock out power grids.
In the declining phase of the solar maximum, high-speed streams develop in the solar wind that is made up of plasma that flows from the sun. These streams continuously buffet Earth’s magnetosphere, producing enhanced geomagnetic activity at high Earth latitudes.
The new findings
The experts found that correlations proved to be strongest between rheumatoid arthritis and giant cell arteritis and geomagnetic activity. Giant cell arteritis incidence regularly peaked within one year of the most intense geomagnetic activity. Rheumatoid arthritis incidence fell to a minimum within one year of the least intense activity. Correlations with the extreme ultraviolet solar radiation indices were less robust and showed a longer response time.
The implications
Other research has suggested greater incidence of rheumatoid arthritis in areas of the US that are more likely to be affected by geomagnetic activity. For example, the heaviest incidence lay along geographic latitudes on the East Coast that were below those on the West Coast. This asymmetry may reflect the fact that high geomagnetic latitudes (areas most subject to geomagnetic activity) swing lower on the East Coast than on the opposite side of the country.
The authors speculate that reduced production of the hormone melatonin (an anti-inflammatory mediator with immune-enhancing effects) and increased formation of free radicals in susceptible people could come into it. One study of 142 electrical power workers found that excretion of melatonin was reduced by 21% on days with increased geomagnetic activity.
For now, however, the authors suggest that “these novel findings warrant examination in other populations and with other autoimmune diseases”.
Click here to read the original research.
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Image credit: Yinan Chen
