Different seasons affect your genes in ways that alter how your immune system functions. (Photo: Hank Morgan/Rainbow/Science Faction/Corbis)
Scientists have a new explanation for why people tend to be healthier in the summertime: Your immune system fluctuates with the seasons, according to a new study from an international team of researchers.
The study, published Tuesday in the journal Nature Communications, notes the first time medical experts have shown a direct connection between the change in climate and our genes, including genes that affect immunity.
Previous research has indicated that certain diseases, such as cardiovascular disease, autoimmune diseases like rheumatoid arthritis and Type 1 diabetes, and psychiatric disorders, are linked to seasonal variation. And with the change of seasons comes a change in the way our immune system functions, as well as changes in the make-up of our blood and fat tissue.
More than 16,000 blood and fatty tissue samples were analyzed from people living around the globe in both the northern and southern hemispheres. The study experts discovered that thousands of genes were expressed differently — meaning when they became active in a cell or tissue — during certain seasons. The types of cells found in the blood also changed according to the season. The analysis concluded that nearly 25 percent of our genes (5,136 out of 22,822 genes tested) alter depending on the time of year.
Scientists were especially focused on two different findings. The first was the gene ARNTL, which was shown to be more active in the summer months. Since prior research in mice indicates that this gene suppresses inflammation — the body’s way of protecting itself — the new finding most likely means that inflammation in humans is higher during the winter, ultimately increasing our odds for developing a host of diseases.
The other, and more surprising, discovery: A group of genes that play a role in our response to vaccination was more active during the cold weather months. This conclusion suggests that some vaccinations may be more effective if received during the winter.
“This is an excellent study which provides real evidence supporting the popular belief that we tend to be healthier in the summer,” Mike Turner, head of infection and immunobiology at the Wellcome Trust, stated in a press release. “Although we are still unclear of the mechanism that governs this variation, one possible outcome is that treatment for certain diseases could be more effective if tailored to the seasons.”