Our immune systems vary with the seasons, according to a study led by the University of Cambridge that could help explain why certain conditions such as heart disease and rheumatoid arthritis¹ are aggravated² in winter whilst people tend to be healthier in the summer. The study, published in the journal Nature Communications, shows that the activity of almost a quarter of our genes³ (5,136 out of 22,822 genes tested) differs according to the time of year, with some more active in winter and others more active in summer. This seasonality⁵ also affects our immune cells and the composition of our blood and adipose⁶ tissue (fat).

 

Scientists have known for some time that various diseases, including cardiovascular disease, autoimmune diseases such as type 1 diabetes⁷ and multiple sclerosis, and psychiatric disorders⁸, display seasonal⁴ variation, as does vitamin D metabolism⁹. However, this is the first time that researchers have shown that this may be down to seasonal changes in how our immune systems function.

 

"This is a really surprising -- and serendipitous¹⁰ -- discovery as it relates to how we identify and characterise the effects of the susceptibility genes for type 1 diabetes," says Professor John Todd, Director of the JDRF/Wellcome Trust Diabetes and Inflammation Laboratory. "In some ways, it's obvious -- it helps explain why so many diseases, from heart disease to mental illness, are much worse in the winter months -- but no one had appreciated the extent to which this actually occurred. The implications for how we treat disease like type 1 diabetes, and even how we plan our research studies, could be profound."

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