Effects of socio-economic factors on research over systemic sclerosis: an analysis based on long time series of bibliometric data

Background Systemic sclerosis (SSc) is a rare detrimental disease warranting global research efforts. Evaluating how socio-economic factors impact country research output on SSc could help to identify solutions advancing research. Methods Publication production on SSc during 1969–2018 and data for structural and policy factors for WHO member countries were collected from public sources. Associations between SSc research output and country-level factors were investigated through panel regression. Difference-in-differences analysis further assessed the causal effects of rare disease legislation. Results SSc publications demonstrated exponential growth ( r = 0.9410, as against an r = 0.8845 after linear adjustment), but were concentrated in high-income countries (HICs). Ten countries, nine of which were HICs, published 12,261 (77.5%) SSc publications but another 87 countries produced none. Gross domestic products (GDP), population and expenditure on research and development were positively associated with SSc publications ( p < 0.001). Higher health expenditure was only found to be associated with increased SSc publications in HICs ( p < 0.001). Rare disease legislation increased annual publication production by 62.8% (95% CI 0.390–0.867; p < 0.001) averagely. In middle-income countries (MICs), the effect was especially swift and lasting. No significant impact was found with GDP per capita, female percentage, and political indicators. Conclusions SSc research output increased over time with substantial country disparities. Effective health policies facilitating research should be expanded especially among MICs to accelerate research advancement.