Prevalence, incidence, and mortality of Raynaud's phenomenon, Sjo gren's syndrome and scleroderma: an umbrella review of systematic reviews

Objectives: To comprehensively review systematic reviews of prevalence, incidence, and mortality of Raynaud's, Sjogren's and Scleroderma, and to identify any research gaps. Methods: An umbrella review of English language systematic reviews was undertaken using PubMed and Embase (OVID) covering the period 2000-2023 (PROSPERO CRD42023434865). The estimate and its corresponding 95% confidence interval were reported when available from each systematic review. The quality of systematic reviews was assessed using the Scottish Intercollegiate Guidelines Network (SIGN) tool. A narrative synthesis was undertaken. Results: Seventeen systematic reviews were identified, of which 1 was for RP, 5 for Sjogren's and 11 for Scleroderma. There were some highquality systematic reviews for Sjogren's and mortality of Scleroderma. However, there were only low-quality systematic reviews of prevalence and incidence of RP and Scleroderma. Furthermore, there were no systematic reviews for the mortality of RP. For RP, the pooled prevalence was 4850 per 100 000; pooled annual incidence was 250 per 100 000. For Sjogren's, prevalence was 60-70 per 100 000; annual incidence was 6.92 per 100 000 and the pooled standardized mortality ratio ranged from 1.38 to 1.48. For Scleroderma, pooled prevalence ranged from 17.6 to 23 per 100 000; annual incidence was 1.4 per 100 000; and the pooled standardized mortality ratio ranged from 2.72 to 3.53. Conclusion: The outcomes of RP were less well described compared with Sjogren's and Scleroderma. There was a lack of high-quality systematic reviews for the prevalence and incidence of RP and Scleroderma. Therefore, further studies and systematic reviews with rigorous case definitions, assessing different ethnic groups are warranted in this area. Lay Summary What does this mean for patients? RP, SS and Scleroderma are rare conditions, which can be distressing for those affected. RP affects blood flow to parts of the body such as the fingers and toes. Sjogren's occurs when the immune system mistakenly targets the tear or saliva glands leading to symptoms including dry eyes and mouth. Scleroderma is a disease that causes hard and thickened skin. These diseases can impact quality of life and increase the risk of other health problems including earlier death. Our knowledge of these conditions, such as how common they are and their health outcomes, is lacking. Previous studies that have reviewed the prevalence (number of existing cases) and incidence (numbe