Nationwide epidemiological survey of primary Sjogren's disease in Japan using the National Database of Designated Intractable Diseases.

Objectives: This study aimed to evaluate clinical and serological factors influencing systemic disease activity in primary Sjögren's disease (SjD) using the European League Against Rheumatism Sjögren's Syndrome Disease Activity Index (ESSDAI) and to identify distinct patient subgroups in a Japanese cohort.

Methods: Data from 7444 patients with ESSDAI ≥5 registered in Japan's National Database of Designated Intractable Diseases were analysed. Univariate and multivariate regression analyses evaluated the impact of demographic and serological factors on ESSDAI scores. K-means clustering identified subgroups based on significant variables.

Results: Male patients exhibited higher ESSDAI scores (coefficient: 0.76, P = .0007), whereas Hashimoto's disease was associated with lower scores (coefficient: -0.53, P = .009). Anti-SS-B/La (coefficient: 1.08, P = .0002) and high titre of antinuclear antibody (ANA) (coefficient: 0.64, P = .02) were associated with increased ESSDAI. Clustering identified three subgroups: a 'classic' SjD group with balanced systemic involvement, a male-specific group with severe manifestations, and a Hashimoto's disease group with milder activity.

Conclusions: Primary SjD in Japan exhibits significant heterogeneity influenced by demographic and serological factors. Male sex and specific autoantibodies correlate with higher systemic activity, whereas Hashimoto's disease is associated with reduced severity. These findings elucidate the need for personalised management and longitudinal studies.