Rheumatoid Arthritis Burden in Middle-Aged Adults (40-59 Years): Evidence from the Global Burden of Disease 2021

Rheumatoid arthritis (RA) is a leading cause of disability worldwide. Although global assessments of RA have been reported, age-specific estimates focusing on middle-aged adults [(MAA); 40-59 years] remain limited.

To quantify the global, regional, and temporal burden of RA among MAA from 1990 to 2021 and project age-standardized trends through 2050.

A population-based descriptive epidemiological study using Global Burden of Disease (GBD) 2021 estimates.

GBD 2021 data (1990-2021) were used to estimate age-standardized incidence (ASIR), prevalence (ASPR), mortality (ASMR), and disability-adjusted life-year rates (ASDR) per 100,000 population among MAA. Temporal trends were assessed using joinpoint regression and expressed as the average annual percentage change (AAPC). Projections to 2050 were generated using a Bayesian age-period-cohort model. Burden patterns were summarized across sociodemographic index (SDI) quintiles and 21 GBD regions.

In 2021, the global ASIR, ASPR, ASMR, and ASDR among MAA were 19.53, 368.73, 0.19, and 56.74 per 100,000 population, respectively. From 1990 to 2021, ASIR and ASPR increased (AAPC = 0.24% and 0.43%), ASMR decreased (AAPC = -1.70%), and ASDR showed minimal net change (AAPC = 0.05%). Substantial variation was observed across SDI quintiles and GBD regions; SDI was positively correlated with ASIR and ASPR and negatively correlated with ASMR. Projections to 2050 indicated an ASIR of 19.22, an ASPR of 367.47, an ASMR of 0.111, and an ASDR of 52.18 per 100,000, with widening credible intervals over time.

Between 1990 and 2021, the RA burden among MAA was characterized by increasing ASIR and ASPR, declining ASMR, and relatively stable ASDR. Projections suggest that ASIR and ASPR will remain near recent levels, whereas ASMR and ASDR will show lower median values over time.