Sjogren syndrome is a phenotypically varied autoimmune disorder that can occur alone in primary Sjogren syndrome or in association with other connective tissue diseases (CTDs), including rheumatoid arthritis, systemic lupus erythematosus (SLE) and systemic sclerosis (SSc). The estimation of the prevalence and incidence of Sjogren syndrome varies depending on diagnostic criteria and study design, making it difficult to estimate geographical and temporal trends. Nonetheless, disease phenotype is influenced by geographical origin, which is a risk factor for systemic activity. Whether mortality in primary Sjogren syndrome is increased compared with that of the general population is not yet known, but extra-glandular manifestations, in particular lymphomas, are clear risk factors for mortality. In CTDs associated with Sjogren syndrome, lymphoma risk seems higher than that of patients with CTD alone, and there is potentially lower disease activity in SLE with Sjogren syndrome and in SSc with Sjogren syndrome than in SLE or SSc alone. In this epidemiological Review, the authors summarize the available evidence relating to the prevalence, incidence, risk factors and mortality associated with the autoimmune disorder Sjogren syndrome, with or without the co-occurrence of other connective tissue diseases. Primary Sjogren syndrome (pSS) affects mostly women, with age at disease onset as well as systemic activity varying according to geographical origin.Assessment of the prevalence of pSS varies according to study methodology, but can be estimated at between 0.01% and 0.05%, although some countries might be under-represented in this estimation.Mortality in pSS seems to be elevated predominantly in patients with extra-glandular manifestations, pulmonary involvement and non-Hodgkin lymphoma.pSS is the autoimmune disease with the most important increased risk of non-Hodgkin lymphoma, especially among patients with extra-glandular manifestations or systemic activity, low complement levels, cryoglobulinaemic vasculitis or rheumatoid factor positivity.Sjogren syndrome can be associated with other connective tissue diseases, mainly rheumatoid arthritis, systemic lupus erythematosus and systemic sclerosis.
