Physical Function in AS Not Affected by Other Comorbidities, Study Suggests

Patricia Inacio PhD avatar

by Patricia Inacio PhD |

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People with ankylosing spondylitis and psoriatic arthritis both are prone to developing additional diseases (comorbidities). However, only in patients with psoriatic arthritis do comorbidities seem to have a negative impact on physical function, according to a study.

The study, “Impact of Comorbidity on Physical Function in Patients with Ankylosing Spondylitis and Psoriatic Arthritis Attending Rheumatology Clinics. Results from the CARdiovascular in rheuMAtology (CARMA) study” was published in the journal Arthritis Care & Research.

Ankylosing spondylitis and psoriatic arthritis are both inflammatory diseases that affect the joints and have a severe impact on physical function.

People with ankylosing spondylitis have an increased rate of other diseases (comorbidities) when compared to the general population, especially cardiovascular problems and osteoporosis.

Similarly, patients with psoriatic arthritis also show higher frequency for cardiac disease, diabetes, metabolic syndrome, and mental health issues. Researchers estimate that over 50% of these patients have more than one comorbidity.

In this study, researchers evaluated the impact of comorbidities on physical function in a group of Spanish patients with ankylosing spondylitis and psoriatic arthritis.

The team analyzed data from the CARdiovascular in rheuMAtology (CARMA) study, an ongoing, 10-year prospective national study in a group of patients with chronic inflammatory rheumatic diseases.

The study included patients with rheumatoid arthritis, ankylosing spondylitis, and psoriatic arthritis together with age- and sex-matched controls from 67 outpatient rheumatology clinics across Spain. Participants were recruited from July 2010 to January 2012.

The study included 1,459 patients, 738 with ankylosing spondylitis and 721 with psoriatic arthritis. Patients with ankylosing spondylitis were diagnosed earlier and were younger at the time of enrollment compared to psoriatic arthritis patients.

Both groups were receiving biologic therapies. Non-steroidal anti-inflammatory drugs (NSAIDs) were more frequent in ankylosing spondylitis patients, while those with psoriatic arthritis took more conventional synthetic disease-modifying anti-rheumatic drugs (DMARDs), combined (synthetic plus biologic DMARDs) therapies and glucocorticoids.

Biological therapies (also known as biologics) are therapies that target individual molecules and tend to work faster than conventional DMARDs.

Regarding the diagnosis of additional diseases, 21% of the patients in both groups had more than one comorbidity.

Some independent variables, such as being female, age, disease activity, radiographic damage, and the use of biologics, were associated with worse physical function in ankylosing spondylitis patients.

While there was an association between physical function and some individual comorbidities (such as obesity, hypertension, hiatal hernia, or thyroid disease), researchers did not identify an association between physical function and comorbidity burden.

However, in patients with psoriatic arthritis, a higher number of comorbidities was associated with worse physical activity.

“[T]he presence of comorbidities may decrease the reported [physical function] of patients with [ankylosing spondylitis] … as the comorbidity burden increases the reported [physical function] of the patients with [psoriatic arthritis] decreases. The detection and control of the comorbidities may yield an integral management of the disease,” the researchers concluded.