Rheumatic Risk Factors Vary by Disease

A series of case-control studies presented at the ACR/ARP Annual Meeting highlighted shared and different risk factors for psoriatic arthritis (PsA), psoriasis, ankylosing spondylitis (AS), and rheumatoid arthritis (RA).

“One of the things that we’ve been studying is how do we know who with psoriasis is going to transition to develop PsA? You can think about this in a variety of different ways. One is that we can understand the pathophysiology,” said study author Alexis Ogdie, MD MSCE, who presented the research. “The second is that you can think about this from a discovery perspective. If we’re in an electronic medical record, is there something we can do with that available data to identify that patient who may be at highest risk for transitioning from psoriasis to PsA?”

The researchers used data spanning 1994 to 2015 from The Health Improvement Network database in the United Kingdom. Patients with at least one code for PsA, psoriasis, AS, or RA were identified and matched to up to 10 controls from the general population who did not have these diseases. More than 100 potential risk factors were considered, including common comorbidities, infections, trauma, and certain medications (including statins).

Final analysis included 7,594 incident PsA cases matched to 75,930 controls, 3,253 incident AS cases matched to 32,530 controls, 111,375 incident psoriasis cases matched to 1,113,345 controls, and 28,341 incident RA cases matched to 282,226 controls. Median age at diagnosis was 48.3 years for PsA, 40.7 years for AS, 43.1 years for psoriasis, and 59.9 years for RA. Sex distribution was about even in psoriasis (52.2% female) and PsA (51.1% female), but there were more female RA cases (68.2%) and male AS cases (69.9%).

Common risk factors across all four groups included past alcohol use (versus non-drinker), uveitis, and pharyngitis. In all four groups, statin use was associated with a lower risk of disease. In some instances, a risk factor for one disease was protective of another: Patients with anemia were more likely to have AS or RA but less likely to have psoriasis. Gout was associated with a greater risk for PsA or RA but a reduced risk for AS. Risk factors that were not significantly associated with any of the four conditions included trauma (overall), trauma to skin, hypertension, myocardial infarction, and urethritis. A strong association was observed between obesity and psoriasis and PsA but not AS and RA. Smoking increased the risk for psoriasis, RA, and AS. Infections were correlated with each of the diseases, but specific infections varied by disease.

“These data generate a lot of hypotheses. They confirm some of the relationships that we already understand, but also raise some new potential risk factors that we need more studies to address in longitudinal cohort studies,” Dr. Ogdie concluded.