Mortality in psoriatic arthritis: Risk, causes of death, predictors for death

Abstract

Background/objectives: Mortality studies in psoriatic arthritis (PsA) have provided inconsistent results. This study aimed to: 1) Estimate trends in mortality rates among PsA patients over calendar time; 2) Evaluate cause-specific mortality rates in patients with PsA compared to the general population; 3) Identify predictors for mortality in PsA.

Methods: The study was carried out at the University of Toronto Psoriatic Arthritis Clinic where patients are followed prospectively according to a standard protocol at 6- to 12- month intervals. Standardized mortality ratios (SMRs) were calculated overall, by age, and by sex with reference to the Ontario population. Causes of death were recorded by ICD9 and ICD10 codes and cause-specific SMRs were computed. Cox regression models were used to identify predictors for mortality among PsA patients.

Results: Among 1490 patients followed over 15062.8 patient-years, 225 (15%) confirmed deaths were recorded (111 females, 114 males). The overall SMR was 0.92 (95% CI: 0.81-1.05), the sex-specific SMRs were 1.08 (95% CI: 0.89-1.30) for females and 0.81 (95% CI: 0.66-0.97) for males. The age-specific SMRs were 3.36 (95% CI: 1.61-6.18), 0.97 (95% CI: 0.68-1.34), 0.88 (95% CI: 0.73-1.06) and 0.86 (95% CI: 0.66-1.11) for 20-39, 40-59, 60-79 and above 80 years of age, respectively. Major causes of death included malignant neoplasms (n=61; SMR=0.97, 95% CI: 0.72-1.28), acute myocardial infarction (n=32; SMR=1.11, 95% CI: 0.74-1.58), and pneumonia (n=14; SMR=2.46, 95% CI: 1.27-4.31). Factors found to be associated with increased mortality include elevated acute phase reactants, presence of comorbidities such as heart disease and cancer, and lower education level.

Conclusion: Young patients with PsA are at increased mortality risk. Better control of comorbidities may reduce this risk.

Keywords: Cause specific mortality; Mortality; Psoriatic arthritis; Standardized mortality ratios.