How Common is Sjogren's?
A Look at Studies on the Prevalence of Primary and Secondary Sjogren's
Before my diagnosis, I had never heard of Sjogren’s. I have wondered since, with all of the support groups out there, how common Sjogren’s actually is. Traditionally, I think primary Sjogren’s was always considered to be a rare disease, which is why none of my doctors suspected I had it.
After doing some online digging, I found out that research on the prevalence of Sjogren’s have significantly varying results, with some showing a prevalence of 0.01% of the total population and others 3% of the total population (making the disease either rare or fairly common). And again, these studies only focused on primary Sjogren’s (pSS) and did not include individuals with secondary Sjogren’s.
I found a fairly recent study from 2020 that investigated the prevalence of pSS in Spain. But the study was particularly helpful because it discussed past research on the prevalence of pSS. The study found that the diagnostic or classification tools used to determine Sjogren’s may have contributed to the disparity in study results. In addition, it is also possible that geographic location impacts the prevalence of Sjogren’s based on genetic or environmental factors. With all of these studies, as expected, pSS was much more common in women than in men.
Primary Sjogren's "could be the most common systemic autoimmune rheumatic disease (SARD) and the most underdiagnosed."
The study concluded that based on the data it analyzed, the prevalence of pSS in Spain was 0.25% (or 1 in every 400 people), which was quite similar to prevalence rates reported in other European studies. In Spain, the prevalence of pSS is about three times lower than that of rheumatoid arthritis (RA), but similar to that of systemic lupus erythematosus (SLE). The study speculated that “pSS could be the most common systemic autoimmune rheumatic disease (SARD) and the most underdiagnosed.”
The United States has only had 2 population-based studies on the prevalence of pSS, but its results are significantly lower than the European studies: “from 0.01 to 0.23% in Europe and 0.02 to 0.06% in America.” It’s possible that this difference is due to geography and different genetic backgrounds. However, it is also possible that the role of healthcare differences between the countries contributed to this difference. Perhaps pSS is just significantly underdiagnosed in the United States (based on my personal experience, I would not be surprised).
A "non-negligible portion of pSS cases in the general population remain undiagnosed."
In all of these cases, pSS should no longer be considered a rare disease based on the definition of “rare” disease in their respective countries (e.g., the US considers a disease to be rare if it affects less than 200,000 people nationwide). The 2020 study also confirmed that “a non-negligible portion of pSS cases in the general population remain undiagnosed.”
Based on other studies, secondary Sjogren’s is also present in 6.5%-19% of those with SLE and 4%-31% of those with RA (depending on the geographic location of the study. Indeed, the Sjogren's Foundation estimates that 4 million people in the United States (around 1.2% of the population) have Sjogren's.
Do you have primary or secondary Sjogren's? What is your understanding of how common Sjogren's is? Please share your story, and like and share the post if you find it interesting or useful.
For a complete copy of the studies, please visit the links below:
