Our immune systems work differently depending on the time of year.
When I was growing up, two sisters who were well into their golden years lived in my neighborhood. Every Thursday afternoon, they would sit on their front porch and pass out candy to all of the kids getting home from school. Except, that is, when it was foggy or drizzly. On cloudy days, the beloved sisters always seemed to be under the weather, and we kids had to wait another week for Candy Day to come around.
We all probably know someone whose health is affected by the weather. Maybe your husband’s knee always gets stiff when rain is coming. Or your sister feels more energetic when the sun is shining. I often find myself coughing on damp evenings. And many people with psoriatic disease experience skin or joint flares during the winter.
According to scientists, there’s a reason why the weather can sometimes make us feel, well, under the weather.
How our immune systems react to the external world
A study published in May 2015 in the journal Nature Communications found evidence for what the researchers call “annual differences in human immunity and physiology.” Put simply, that means that our bodies — including our immune systems — work differently depending on what time of year it is. According to the findings, certain parts of our immune system are more active during the summer or the winter, depending on where you live.
Using large collections of genetic information from all over the world, researchers analyzed which genes were upregulated, or turned on, at different times of the year. When they compared genes from people in the United States, Australia, Europe and Africa, they found some striking similarities — and differences.
For example, people in northern Europe had a more active immune system during the winter months, the researchers reported. During those dreary months, the body produced more pro-inflammatory cytokines. Cytokines are proteins released by immune cells that can jump-start an inflammatory attack. We need these cytokines to fight off a cold or virus. But these are the same cytokines that are involved in many inflammatory diseases, including psoriasis and psoriatic arthritis, as well as rheumatoid arthritis, diabetes and cardiovascular disease.
Researchers also found that people living in different climates have different needs. Take, for example, those living in The Gambia, in West Africa. According to the study, levels of a kind of an immune cell known as white blood cells increase from June to October — which just happens to be the rainy season, when risk for infectious diseases like malaria is highest.
(By the way, it seems like your immune system knows what hemisphere you’re living in. Researchers found that gene upregulation followed the pattern of the seasons no matter what time of year you get your seasons. That means that genes that were more active in the summer months in Europe were also more active during the summer months in Australia — even though the Australian summer starts in December.)
Evolution offers an explanation for why the immune system is more active at certain times of the year. In Africa, it’s raring to go during the summer because that’s when people are most susceptible to infection. In other climates, such as northern Europe, winter might have been the riskiest time of year. Competition between the species was fiercest during the winter, the researchers noted. That’s probably because resources were more scarce during that bleak and barren time. To give people the best shot at providing for themselves and their families, the immune system stayed in fighting shape.
Inflammation and the immune system
There are some advantages to getting a little extra help from our immune systems at certain times of year. But anyone with an inflammatory illness — like psoriatic disease — knows that a revved up immune system can backfire on our overall health.
As the researchers noted, increased immune activity could be why more people die from cardiovascular disease during the winter than during the summer, and it could also be why the risk for rheumatoid arthritis and diabetes peaks in the winter. And probably why Candy Day didn’t seem to happen as much when the weather was bad.
Past research shows that psoriasis can get worse in the winter — possibly due to decreased sunlight and the colder air. And as with rheumatoid arthritis, if you have psoriatic arthritis, the winter may leave your joints feeling extra creaky and achy. Learn how you can fight flares in winter with the free Winter Flares Guide from the Patient Navigation Center.
Driving discovery, creating community
For more than 50 years, we’ve been driving efforts to cure psoriatic disease and improve the lives of those affected. But there’s still plenty to do! Learn how you can help our advocacy team shape the laws and policies that affect people with psoriasis and psoriatic arthritis – in your state and across the country. Help us raise funds to support research by joining Team NPF, where you can walk, run, cycle, play bingo or create your own fundraising event. If you or someone you love needs free, personalized support for living a healthier life with psoriatic disease, contact our Patient Navigation Center. And keep the National Psoriasis Foundation going strong by making a donation today. Together, we will find a cure.