Common risk factors among patients with rheumatoid arthritis (RA), psoriatic arthritis (PsA), psoriasis, and ankylosing spondylitis (AS) include infections, lifestyle factors, and metabolic disease. Statin use is negatively associated with development of any of these diseases, researchers reported in a study published in the Journal of Rheumatology.

The investigators sought to compare potential risk factors for the 4 diseases by conducting 4 separate case-control studies in parallel. They extracted data from 1994 to 2015 from The Health Improvement Network (THIN), a general practitioner database in the United Kingdom.

The study authors identified 7594 incident cases of PsA, 111,375 incident cases of psoriasis, 28,341 incident cases of RA, and 3253 incident cases of AS and matched them to 75,930, 1,113,345, 282,226, and 32,530 control individuals, respectively. Participants’ median age at diagnosis was 48.3 years (interquartile range [IQR] 38-59), 40.7 (IQR 31-54), 43.1 (IQR 31-54), and 59.9 (IQR 48-71), respectively. Sex distribution was similar in the PsA and psoriasis groups, the RA group had more women (68%), and the AS group had more men (70%). The mean follow-up was 6.4 to 7.2 years and was slightly longer in the control group.

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Multivariable analyses revealed shared and different risk factors in the 4 disease groups. PsA was associated with alcohol use (odds ratio [OR] 1.67), obesity (1.64), a previous diagnosis of gout (2.19), pharyngitis (1.23), skin infection (1.37), and trauma (1.22). Psoriasis was linked to smoking (1.60), obesity (1.27), alcohol (1.27), previous myocardial infarction (1.43), and trauma to bone (1.29).

The analysis also showed that RA was associated with smoking (1.56), coronary artery disease (1.28), anemia (1.26), a previous diagnosis of gout (1.67), osteoporosis (1.43), inflammatory bowel disease (IBD) (1.56), and trauma to the joint (1.25). AS was linked to current smoking (1.31), previous drinking (1.51), anemia (1.57), osteoporosis (2.93), uveitis (37.93), IBD (5.46), and gastrointestinal infection (1.32).

Among the shared findings, both PsA and psoriasis diagnoses were associated with obesity and moderate alcohol intake, PsA and AS diagnoses were associated with uveitis, and PsA and RA were linked to a previous diagnosis of gout and history of moderate alcohol intake. Psoriasis and RA were associated with current and previous smoking and myocardial infarction, and psoriasis and AS were associated with current smoking.

Both RA and AS were linked to current smoking, previous moderate drinking, anemia, osteoporosis, and IBD. PsA, psoriasis, and RA had previous smoking as a shared risk factor, and psoriasis, RA, and AS had current smoking as a shared risk factor. Statin use was inversely associated with all 4 diseases.

The study authors noted that their findings are limited by their use of an electronic health record, although they assume this to be nondifferential misclassification. In addition, missed diagnoses of inflammatory arthritis are common in patients with PsA and likely the other groups and could possibly influence the findings. Furthermore, the case-control design is a limitation as these inflammatory diseases may be ongoing for many years before diagnosis.

“Future cohort studies are needed to further explore the causal effects of the identified predictors,” stated the researchers. “Additionally, these future studies will examine the positive predictive value of combinations of these risk factors in identifying patients with early inflammatory disease.”

Disclosure: Some [or one] study author(s) declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.


Meer E, Thrastardottir T, Wang X, et al. Risk factors for diagnosis of psoriatic arthritis, psoriasis, rheumatoid arthritis, and ankylosing spondylitis: A set of parallel case-control studies. J Rheumatol. Published online August 1, 2021. doi:10.3899/jrheum.210006