Rate, risk factors and causes of mortality in patients with Sjögren's syndrome: a systematic review and meta-analysis of cohort studies

Objectives: There is conflicting evidence regarding prognosis in patients with primary SS (pSS). The aim of this study was to estimate the rate, risk factors and causes of mortality in patients with pSS through a systematic review and meta-analysis.

Methods: Through a systematic review of multiple databases through October 2014, we identified cohort studies reporting relative risk (compared with standardized population), risk factors and causes of mortality in patients with pSS. We estimated summary risk ratios (RRs) with 95% CIs using random effects model.

Results: We identified 10 studies with 7888 patients (91% females) with pSS, of whom 682 patients died over a median average follow-up of 9 years. The pooled standardized mortality ratio in patients with pSS was 1.38 (95% CI 0.94, 2.01). Leading causes of mortality were cardiovascular diseases, solid-organ and lymphoid malignancies and infections; however, it is unclear whether these observed causes were overrepresented in patients with pSS as compared with the general population. Risk factors associated with increased mortality were advanced age at diagnosis [RR 1.09 (95% CI 1.07, 1.12)], male sex [RR 2.18 (95% CI 1.45, 3.27)], parotid enlargement [RR 1.81 (95% CI 1.02, 3.21)], abnormal parotid scintigraphy [RR 2.96 (95% CI 1.36, 6.45)], extraglandular involvement [RR 1.77 (95% CI 1.06, 2.95)], vasculitis [RR 7.27 (95% CI 2.70, 19.57)], anti-SSB positivity [RR 1.45 (95% CI 1.03, 2.04)], low C3 [RR 2.14 (95% CI 1.38, 3.32)] and C4 [RR 3.08 (95% CI 2.14, 4.42)] and cryoglobulinaemia [RR 2.62 (95% CI 1.77, 3.90)].

Conclusion: pSS is not associated with an increase in all-cause mortality as compared with the general population. However, a subset of patients with extraglandular involvement, vasculitis, hypocomplementaemia and cryoglobulinaemia may be at increased risk of mortality and require close follow-up.