Prevalence and factors associated with osteoporosis and bone mineral density testing in psoriatic arthritis

Objectives: To determine bone mineral density (BMD) in psoriatic arthritis (PsA) patients, factors associated with undergoing BMD testing, and the effect of PsA clinical activity on BMD.

Methods: Patients attending the University of Toronto PsA Clinic with a BMD from cohort inception to January 2019 were included. Descriptive statistics summarized lumbar spine, femoral neck and total hip T-scores. Cox proportional hazard regression identified predictors for BMD testing. Logistic regression analysis determined odds of having normal (T-score ≥ -1.0) versus osteoporotic range BMD (T-score ≤ -2.5). A multi-state model determined factors associated with BMD state changes over time.

Results: Of the 1479 patients, 214 had BMDs. Mean T-scores at the lumbar spine, femoral neck and total hip were -0.30±0.32, -1.10±1.04 and -0.45±0.42 respectively. Osteopenia and osteoporosis occurred in 45.27% and 12.94% of patients. Increasing age, menopause, elevated acute phase reactants, biologic, methotrexate and systemic glucocorticoid use were associated with a higher chance of undergoing BMD testing. Increased BMI and biologic use were associated with a lower chance of having osteoporotic range BMD. In multi-state analysis, polyarthritis may portend lower BMDs over time, although this did not achieve statistical significance due to low patient numbers.

Conclusions: The prevalence of osteopenia and osteoporosis in the PsA cohort were similar to the general population. Clinicians are using osteoporosis risk factors and PsA disease severity markers to select patients for BMD testing. Polyarticular disease may portend worse BMDs. Biologic use and increased BMI appear to have a protective effect.

Keywords: Bone loss; Epidemiology; Osteoporosis; Psoriatic Arthritis.