Demographics and Certain Symptoms Linked to Increased Disability in AS Patients, Korean Study Finds

Male sex, older age at diagnosis, and the presence of certain symptoms are all risk factors for overall disability in patients with ankylosing spondylitis (AS), a study from South Korea reported.

The study, “Comorbidity, disability, and healthcare expenditure of ankylosing spondylitis in Korea: A population-based study,” was published in the journal PLOS ONE.

To assess the burden of AS and investigate factors associated with comorbidities (the simultaneous presence of other diseases, related in some way to the main disease), disability, and healthcare expenditure in South Korea, a group of researchers from Seoul National University College of Medicine collected data from the National Health Insurance Service-National Sample Cohort, a large sample of the Korean population that submitted medical claims from 2002 to 2013.

A total of 1,111 individuals with ankylosing spondylitis and 5,555 people without AS matched by age, sex, income, and geographic region (called controls) were analyzed.

The presence of extra-articular manifestations (EAMs) — all the conditions and symptoms which are not directly related to the locomotor system — as well as other diseases, mortality, and disability in AS patients were compared to the controls. Annual health expenses per patient was also analyzed.

The odds of experiencing physical disabilities were five times higher in AS patients. This risk was even higher for severe physical disability —  11 times more likely in AS patients. Overall mortality rates were not significantly different when compared to controls.

The presence of EAMs or comorbidities were also significantly increased in ankylosing spondylitis patients.

Twenty-eight percent of AS patients experienced at least one extra-articular manifestation and 3 percent had multiple EAMs during follow-up.

Uveitis — inflammation of the uvea, the middle layer of the eye — was the most prevalent EAM, affecting 20 percent of those with ankylosing spondylitis, who had a nine-fold increased risk of developing this inflammation. A small percentage of patients also exhibited inflammatory bowel disease and psoriasis. 

Researchers found that male sex, presence of an EAM, and older age at diagnosis were the strongest risk factors for overall disability or physical disability, regardless of AS severity.

Male sex was the highest factor of all, increasing the chances of disability by three times.

Of note, higher income level was inversely correlated with disability.

Average annual health expenses for patients with ankylosing spondylitis were 3.3 times higher than for controls, but patients who were treated with biologic agents spent almost 25 times more due to the high cost of these medications.

This analysis showed that among South Koreans with ankylosing spondylitis, demographic factors and systemic manifestations including EAMs and comorbidities were associated with increased disability and healthcare expenditures.

“Despite its limitations, the present study showed that AS is not only a painful disease of the musculoskeletal system, but also has systemic consequences such as EAMs and other comorbidities, and that these factors are associated with increased disability rates and healthcare expenditures,” researchers wrote.

“Early diagnosis and active treatment for the patients having such risk factors might help reduce the burden of disease on the patients, on the healthcare system, and on society,” they concluded.