Why Do I Get Sick More During Winter? Science Has Another Reason For Us To Be Glad Summer's Almost Here

Good news: In addition to the warmer weather just around the corner for many of us, we can also look forward to stronger immune systems this summer: According to a study at the University of Cambridge, about a quarter of genes related to our immune system are season-dependent. Our resistance to disease apparently fares best in the summer and worst in the winter, so let's get ready to break out those sandals, shall we?

The study measured gene expression in cells from the blood and tissue samples of over 16,000 people all over the world. As it turns out, the time of year when the samples were taken played a role in which immune-system-related genes were expressed. The researchers suspect that the changes in gene expression throughout the year are due to external light and temperature cues.

The results showed some differences in different locations. For example, in Gambia, the presence of disease-fighting cells peak during the "rainy season" all the way from June to October, when they're needed to fight off diseases like malaria.

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But what many of the cells examined had in common through the world was that they showed greater gene expression during summer in the hemisphere where the participants were located (since Australia's summer is December through February, the Australians' genes were most highly expressed then). The one exception to this pattern was Iceland, which has nearly 24 hours of daylight in the summer and 24 hours of darkness in the winter.

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While this concept rings intuitively true for those of us who remember strings of classmates being absent from school during winter, the genes examined in the study don't just apply to your typical cold or flu. Some are also are involved in fighting off diabetes, heart disease, arthritis, and even mental illness, said John Todd, one of the authors of the study, in a press release. In addition, one of the genes examined suppresses inflammation, so drug companies targeting this problem may benefit from knowing that it's more likely to rear its head in the winter. One set of genes showed the reverse pattern: Genes associated with our response to vaccination were more active in the winter, so people may benefit from receiving vaccinations during the winter months. Todd also speculated that if climate and light fluctuations themselves are affecting our immune systems (though it also seems possible that these cycles are in our genes no matter where we travel), "it is perhaps understandable that people want to head off for some 'winter sun' to improve their health and well-being." There's an idea we can all get on board with.

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