Seasons affect how human genes work

May 12, 2015, 5:42 PM EDT
Alex Haugom watches Karli Mascarenas slide down their snow slide they built in Wash Park May 10, 2015 as residents woke up to broken limbs from trees from an overnight storm dumping 5-10 inches of snow.
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Findings published in Nature Communications point to an increase in the body's immune system functions that fights infections, but that increase in work also raises risk of inflammation, causing heart attacks, stroke and diabetes during colder months. The BBC reports:

The international team of researchers analysed blood and tissue samples from more than 16,000 people living around the world.
Of the 22,000 genes they scrutinised - which is nearly all the genes humans possess - a quarter showed clear signs of seasonal variation.
The gene changes that interested the researchers the most were ones involved with immunity and, specifically, inflammation.
During cold, winter months - December to February for people living north of the equator and June to August for those in the southern hemisphere - these genes were more active.
When they studied people living close to the equator, where the temperatures are fairly high all year round, they noticed a different pattern. Immunity and inflammation was linked to the rainy season, when diseases such as malaria are more rife.
Prof John Todd, a geneticist at the University of Cambridge, said: “Until now the seasonal peaks in cardiovascular deaths, multiple sclerosis, Seasonal Affective Disorder (SAD) and schizophrenia have been well known but the cause has been a mystery.”
The latest work suggests that our own immune systems could be “tipping us over the edge” into illness - or even death. In the future, doctors may be able to reduce this peak, by prescribing medicines, such as statins, diabetic drugs and anti-depressants on a seasonal basis, the scientists suggested.
In England and Wales, the winter peak in cardiovascular deaths accounts for an additional 20,000 fatalities each year, and people are most likely to be diagnosed with diabetes between November and February.