Our Immune System is Seasonal

Some diseases have a higher incidence in certain seasons. For example, the incidence of heart attack deaths, rheumatoid arthritis, type 1 diabetes, and some psychiatric conditions is greater in winter. These diseases also are characterized by inflammation.

A European team examined thousands of blood samples from ethnically diverse populations in the Northern and Southern hemispheres and the equatorial region to see if seasonal differences could be identified in the immune system.

They discovered that almost one quarter of the genes related to inflammation and immunity have seasonal variations. Some increase activity in the summer, others decrease; similarly in the winter. In regions of Africa, where there is less temperature change, the genetic changes were evident in the rainy season.

This could be an evolutionary response to diseases more prevalent in different seasons. However, it could also result, when abnormal responses occur, in disease states (like autoimmune disorders).

Right now this does not have any clinical applications, except to demonstrate thee complex interaction of humans with their environment.