AS Patients at Greater Risk of Other Inflammatory Diseases, Taiwanese Study Reports

People with ankylosing spondylitis (AS) are at a greater risk of developing certain inflammatory diseases — specifically, Behcet’s disease, Buerger’s disease, acute anterior uveitis, sarcoidosis, and psoriasis, according to a Taiwanese study.

The study, “Risk of immune-mediated inflammatory diseases in newly diagnosed ankylosing spondylitis patients: a population-based matched cohort study,” was published in the journal Arthritis Research & Therapy.

Immune-mediated inflammatory diseases (IMIDs) are a group of conditions characterized by the dysregulation of cytokines — small proteins that act as chemical messengers between cells of the immune system — resulting in chronic inflammation in targeted organs or systems.

IMIDs are estimated to affect around 3% to 7% of a given country’s population, and previous studies have shown that people with one IMID are at risk of developing another.

AS is the most common form of spondyloarthritis, a family of inflammatory rheumatic diseases that cause arthritis and are considered IMIDs. AS is strongly associated with spondyloarthritis-related IMIDs, including acute anterior uveitis (inflammation affecting the eye), psoriasis (inflammation affecting the skin), and inflammatory bowel disease (IBD).

However, an AS patient’s risk of developing an IMID other than those related to spondyloarthritis remains unclear.

Researchers have now evaluated the occurrence (and the risk) of 15 IMIDs in people newly diagnosed with AS in Taiwan.

This retrospective, population-based study analyzed the data of 30,911 people diagnosed with AS between 2006 and 2012, and compared to 309,110 age- and sex-matched healthy people, using the Taiwanese National Health Insurance Research Database (NHIRD).

This electronic database, derived from claims (administrative) data of national health insurance beneficiaries, covers up to 99.9% of the Taiwanese population.

To distinguish between IMIDs occurring at the same time or earlier than AS, the team only considered IMIDs diagnosed more than three months after AS diagnosis. Disease risks were calculated after adjusting for age, sex, comorbidities, number of hospital visits, and medication use during follow-up.

For both groups, mean age was 42 years, and 62.9% were men.

Results showed that newly diagnosed AS patients had a significantly increased risk of developing Behcet’s disease (inflammation affecting the blood vessels), Buerger’s disease (characterized by narrowing or blockage of blood vessels), acute anterior uveitis, sarcoidosis (characterized by small patches of red and swollen tissue in organs), and psoriasis, compared with non-affected people. These risk factors rose by a range of less than 1 to that of 26 times greater risk.

However, these AS patients were significantly less likely to develop rheumatoid arthritis (inflammation affecting the joints).

“These significant associations indicate potential shared or distinct genetic, [disease-causing mechanisms] and clinical relationships between AS and these IMIDs and also suggest that physicians should survey symptoms and signs related to the positively correlated IMIDs when managing AS patients,” the researchers wrote.

The team noted that the absence of an association between AS and inflammatory bowel disease in this study may be due to the low occurrence of IBD in Taiwan, or the fact that IBD onset in these patients occurred mostly prior to AS diagnosis — suggesting a potential delay in AS diagnosis.

Some potentially influencing factors — such as socioeconomic status, smoking and drinking history, and family history — were not available in the database, the researchers also noted, adding that these findings — especially those related to IBD — may not be generalized to non-Taiwanese populations.

Future studies are required to confirm these associations in other populations, to better understand the role of AS in the development of these IMIDs, and to identify potential associated risk factors.