Smoking was found to be positively associated and statin use negatively associated with the development of psoriatic arthritis (PsA), psoriasis (PsO), rheumatoid arthritis (RA), and ankylosing spondylitis (AS), according to study findings published in The Journal of Rheumatology.

Chronic inflammatory diseases, including PsA, PsO, RA, and AS, can cause significant disability and decreased quality of life. However, early disease diagnosis can help prevent permanent joint damage and improve long-term outcomes.

Researchers of the current study compared risk factors for the diagnosis of PsA. PsO, RA, and AS.

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Four parallel case-control studies were conducted among patients with PsA, PsO, RA, and AS. Data from 1994 to 2015 were collected from the Health Improvement Network in the UK. Patients were selected from the database based on validated code lists and matched by age, sex, practice, and year of diagnosis.

Potential risk factors were identified from conditions coded in the time preceding diagnosis. A multivariable logistic regression model was developed for each disease, using automated stepwise regression to identify significant risk factors.

Patients with incident disease and matched control participants (PsA, 7594 patients and 75,930 control participants; PsO, 111,375 patients and 1,113,345 control participants; RA, 28,341 patients and 283,226 control participants; AS, 3253 patients and 32,530 control participants) were included in the analysis.

Shared and distinct risk factors included the following:

  • PsA: Obesity, pharyngitis, and skin infections
  • PsA and PsO: Obesity and moderate alcohol intake
  • PsA and AS: Uveitis
  • PsA and RA: Preceding gout
  • RA and AS: Current smoking, former moderate drinking, anemia, osteoporosis, and inflammatory bowel disease
  • All: Current smoking

In addition, statin use was inversely associated with PsA, PsO, RA, and AS.

One limitation of the study was the potential misclassification of exposures and outcomes in the electronic medical records. Another limitation was delayed diagnosis, which may not have distinguished risk factors for early disease with features of existing disease in the case-control analysis. This was seen with RA and PsA that was misdiagnosed as gout as a risk factor, but could have reflected a late diagnosis.

The researchers concluded, “This was a hypothesis-generating study; the goal was not to identify causal or etiologic associations (the case-control design also limits this ability). Future cohort studies are needed to further explore the causal effects of the identified predictors. Additionally, these future studies will examine the positive predictive value of combinations of these risk factors in identifying patients with early inflammatory disease. Such combinations of risk factors can then be used in trials to enroll high-risk patients in interven­tion studies aiming to prevent disease.”

Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ 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 January 1, 2022. doi:10.3899/jrheum.210006