In my own experience and talking with people with chronic conditions, many notice a seasonal component to flare ups and remission. Spring was a time early on in my Crohn's tenure that was a bit more tumultuous. I'd also have a lot more seasonal allergies, and I wondered if these were somehow related. Interestingly, now that my illness is in remission I no longer have those allergies. I don't know why, but I'm just gonna roll with it.
So what does the science say about the seasons and chronic conditions?
Vitamin D levels are related to Ulcerative Colitis activity. Not exactly a study on seasons, but obviously we get a lot less sun exposure in the winter months. A 2013 study reports that 68% of people in the "deficient" group had active UC symptoms, compared to 33% in the "sufficient" group. It's not really understood why this happens, but there is a relationship. In China, UC flares tend to be more common in the spring and summer months. A side effect of lower Vitamin D from the winter?
Being born in the Fall increases your chances of food allergies. If you're Caucasian and are born in around this time of year, you're almost 2.5 times more likely to have food allergies than someone born in a different season. Why? Again, we know the relationship exists but the reason is elusive. But, like Ulcerative Colitis, Vitamin D deficiency is implicated. For people with eczema, this condition may enhance low vitamin D risk and is a potential reason why these 2 conditions often appear together.
Your Rheumatoid Arthritis is less likely to bother you in the Fall. Good news, RA people. This time of year tends to lead to less symptoms, according to a 2007 study. They looked at disease activity trends in over 1600 people with RA and found that patients are more likely to report greater RA symptoms in the spring compared to the fall, and laboratory tests tend to back up patient reports. Interestingly, the patient's physician tended to rate RA activity the same throughout the year and not notice these seasonal changes.
A May birthday is associated with increased risk for Multiple Sclerosis. Ok, these researchers got really specific and looked at 42,000 people across several countries by month for the lowest and highest risks for developing MS. People born in May (in the Northern Hemisphere) were 19% more likely to have MS than those born in November. In general, people born between March and June had higher MS rates. Why? One possibility is lower vitamin D levels in pregnant women during the winter months in these regions.
Crohn's Disease is more likely to show up in the spring/summer. Funny, I was diagnosed in May. One study in 2006 found that people are more likely to be diagnosed with Crohn's disease in the spring to summer months. Similar trends were found for UC, but weren't statistically significant. Why might this be? One explanation given are seasonal changes in how the immune system works. Shorter days in the winter seem to enhance immune system functioning, but winter can also be a stressful time (not just because of the holidays). It's not entirely clear how these changes might bring on IBD, but it seems like a risk factor. Other possible reasons might be increased illness in the winter months and use of antibiotics, which are considered another risk factor for IBD development. Flu shots don't seem to be a trigger.
Being born in the Spring increases the odds of having Type 1 diabetes. Are we noticing a trend here? This study looked at regions in the United States, and found that people who live up north and have T1D are more likely to be born between April and July, and those born in the fall are less likely to have it. Vitamin D levels are discussed again as a possible cause.
The takeaway message here is that there are two seasonal components to chronic illnesses that are caused by a haywire immune system (technical term): the season you were born may have influenced you getting the illness in the first place, and now that it's here the seasons may influence when you feel sick and when you feel well. Vitamin D seems to be the main focus of these studies. This is not to say if you have a chronic autoimmune condition you should load up on Vitamin D. You can take too much and develop toxicity. But, it is important to monitor your vitamin D levels as part of your routine care, if you're not already. Talk more with your doctor about this.