The epidemiology of polyautoimmunity in Sjögren's syndrome (secondary Sjögren's syndrome - sSS) is not well defined and has not been investigated before using a systematic approach. We conducted a systematic review of the epidemiology of sSS associated with rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), scleroderma, and myositis, assessing the prevalence rates (PRs) and clinical and serological features of sSS.
A systematic literature search of PubMed and Embase databases (updated to March 2016) was performed to identify all published data on PR, demographic proﬁle, clinical manifestations, laboratory features, and causes of death associated with sSS. The PR's of sSS were summarized with PRs and 95% confidence intervals (CIs).
The literature search identified 1639 citations, of which 42 fulfilled the inclusion criteria. Only 19 studies were of moderate to good quality and were selected for the meta-analysis. According to a random-effects model, the pooled PR for sSS associated with RA was 19.5% (95% CI 11.2 to 27.8) and the pooled PR for sSS associated with SLE was 13.96% (95% CI 8.88 to 19.04). The female/male ratio of sSS in the RA population was 14.7 (95% CI 7.09 to 256) and in the SLE population was 16.82 (95% CI 1.22 to 32.4).
Prevalence rates of sSS vary widely in different populations. Both meta-analyses conducted in the RA and SLE populations were characterized by a high degree of study heterogeneity. The results of this meta-analysis highlight the need for better quality population studies.