Background/Purpose: Psoriasis is a systemic inflammatory disorder associated with cardiometabolic and other comorbidities. Psoriasis frequently precedes development of psoriatic arthritis (PsA), and comorbidities in psoriasis may help identify those with psoriasis at greatest risk of developing PsA. We aimed to examine the association of comorbidities with development of PsA in an incident cohort of psoriasis.

Methods: A population-based incidence cohort of psoriasis subjects ≥18 years of age and first diagnosed in 2000-2010 was identified. Complete medical records of all potential psoriasis subjects were reviewed, and psoriasis was defined as a confirmatory diagnosis in the medical record, either by a dermatologist’s or physician’s description of the lesions or by a skin biopsy, if available. Doubtful cases were reviewed by a dermatologist. Psoriasis severity was defined based on the body surface area involved, sites involved, and requirement for phototherapy or systemic therapy. PsA cases were defined as patients fulfilling ClASsification of Psoriatic ARthritis (CASPAR) criteria for PsA. Diagnosis codes (≥2 codes at least 30 days apart) within a five-year look-back period were used to determine the presence of comorbidities; ≥1 year of available medical history was required. Comorbidities were defined using 159 categories per modified Clinical Classification Software. Age-, sex-, and race-adjusted Cox models were performed for association of baseline comorbidities in psoriasis with the incidence of PsA.

Results: There were 871 incident cases of psoriasis. Excluding those with < 1 year of prior medical history (n=54) and those who were diagnosed concurrently with PsA (n=15), 802 psoriasis patients were analyzed, with a mean age of 46.3 (SD 16.9) years; 52.5% were females, and 78.7% and 3.2% patients had moderate and severe psoriasis, respectively. At psoriasis incidence, 34.5, 17.1, 11.8, 9.7, 5.9, 16.7, and 4.2% of the psoriasis patients had 0, 1, 2, 3, 4, 5-9, and ≥10 comorbidities. The median follow-up in the cohort was 14.7 years (IQR 12.1-17.4), and 23 patients developed PsA. Risk of developing PsA decreased with age (HR 0.76, 95% CI 0.57-1.00 per 10 years of age) and was higher for non-white population compared to whites (HR 4.02, 95% CI 1.58 -10.24). Higher risk of developing PsA was noted with ≥2 comorbidities (HR 2.53, 95% CI 1.05-6.11) and ≥5 comorbidities (HR 3.19, 95% CI 1.07-9.50). Comorbidities associated with significantly higher risk of PsA were other nervous system disorders (e.g., carpal tunnel syndrome and peripheral neuropathy), spondylosis, anxiety, mood disorders, other mental disorders, and fibromyalgia.

Conclusion: A higher number of comorbidities at psoriasis diagnosis was significantly associated with the development of PsA. Nonspecific musculoskeletal disorders, such as peripheral neuropathy, fibromyalgia, and back disorders as well as the presence of mood disorders and/or anxiety could help identify those that should be monitored closely for development of PsA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/multimorbidity-in-psoriasis-as-a-risk-factor-for-psoriatic-arthritis-a-population-based-study/