Summertime and the Livin’ is Easy
In George Gershwin’s classic tune, “Summertime,” the fish are jumpin’ and the livin’ is easy. Summertime is a metaphor for security, bounty, and good times in the classic aria from “Porgy and Bess.” And now, it’s serves to underscore new medical research, which shows that summertime really is easier when it comes to our health.
According to researchers at the University of Cambridge, summertime is easier on our bodies because it somehow alters certain genes—and that, in turn, affects the immune system. In short, say the scientists in a report in Nature Communications, inflammation in the body subsides in summer. Of course, the flip side is that in winter, inflammation gets worse. And that may explain the curious rise in cases of inflammation-mediated illnesses, such as cardiovascular disease and even some forms of mental illness (think Seasonal Affective Disorder, or SAD). Certain auto-immune diseases such as type 1 diabetes, or multiple sclerosis, also appear to be more prevalent in winter.
This seasonal increase in inflammation-related diseases during winter has long been observed. But until now, it defied explanation. Now investigators think they know what’s going on. Remarkably, something about the changing seasons appears to switch certain genes on or off. "This is a really surprising -- and serendipitous -- 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.”
In essence, genes that suppress inflammation tend to be more “switched on” during summer, while genes that promote inflammation are switched off. In winter, the reverse occurs, at least at latitudes where the terms summer and winter have seasonal meaning. That would include most of the United States, as only limited areas of the United States fall within the subtropical zone.
Scientists still haven’t pinned down the exact cause of these seasonal changes. Obvious possibilities include changing light, temperature, or humidity associated with the changing seasons. Some experts have speculated for years that falling blood levels of vitamin D, which is related to sunlight exposure, might be linked to changes in immune system function. But the exact nature of the relationship between the seasons and immune function remains to be discovered.
Xaquin Castro Dopico, Marina Evangelou, Ricardo C. Ferreira, Hui Guo, Marcin L. Pekalski, Deborah J. Smyth, Nicholas Cooper, Oliver S. Burren, Anthony J. Fulford, Branwen J. Hennig, Andrew M. Prentice, Anette-G. Ziegler, Ezio Bonifacio, Chris Wallace, John A. Todd. Widespread seasonal gene expression reveals annual differences in human immunity and physiology. Nature Communications, 2015; 6: 7000 DOI: 10.1038/ncomms8000