Comparative analysis of the burden of aged rheumatoid arthritis in China and globally from 1990 to 2021, with projections to 2044: Findings from the Global Burden of Disease Study 2021

To the Editor: Rheumatoid arthritis (RA) is a chronic autoimmune disease that disproportionately affects older adults, with a growing incidence of onset occurring due to the global aging of populations.[1] Aged RA—encompassing both elderly-onset RA and persistent earlier-onset cases—carries a heightened burden due to accelerated joint damage, increased comorbidities, and high mortality risk.[2] However, population-based evidence on the long-term burden and epidemiological trends of aged RA—particularly in China—remains limited. Using data from the Global Burden of Disease Study 2021 (GBD 2021), we analyzed trends in the RA burden among the elderly in China from 1990 to 2021 and compared them with global patterns, including estimates of smoking-attributable burden. We used data from the GBD 2021, which tracks 369 diseases and injuries and 87 risk factors in 204 countries and territories. RA was defined according to the 1987 American College of Rheumatology criteria.[3] Aged RA was defined as RA occurring in individuals aged ≥60 years, consistent with previous GBD studies and WHO classifications, particularly those used in low- and middle-income settings. This threshold is further justified by regional life expectancy trends, as the average life expectancy in China has steadily increased, making ≥60 years a meaningful and policy-relevant cutoff for assessing the age-related disease burden.[2,4,5] Temporal trends from 1990 to 2021 were assessed using Joinpoint regression. Projections of RA burden through 2044 were generated using the Bayesian age-period-cohort (BAPC) model and the Norpred framework. Detailed descriptions of GBD methodology are available elsewhere.[6] All statistical analyses were conducted using R version 4.3.2 (R Foundation for Statistical Computing, Vienna, Austria; https://www.r-project.org/), with statistical significance defined as a two-sided P-value <0.05. In 2021, older adults (aged ≥60 years) accounted for a substantial proportion of the RA cases both globally and in China. Compared to global estimates, the proportions of aged RA in China is slightly lower in prevalence (42.3% vs. 44.2%), incidence (32.7% vs. 33.4%), deaths (86.6% vs. 88.9%), and disability-adjusted life-years (DALYs, 48.4% vs. 50.4%) [Supplementary Figure 1, https://links.lww.com/CM9/C624]. The global age standardised rates of prevalence (ASPR), incidence (ASIR), mortality (ASMR), and DALYs were 726.95 per 100,000 population, 30.32 per 100,000 population, 3.20 per 100,000 population, and 143.22 per 100,000 population, respectively. Compared with global patterns, China exhibited lower ASIR (29.59 per 100,000 population) but higher ASPR (748.41 per 100,000 population), ASMR (3.81 per 100,000 population), and age-standardized DALYs rate (153.44 per 100,000 population) among the elderly, indicating a relatively greater RA burden in aging population [Table 1]. Table 1 - Comparison of the burden and temporal trends of aged rheumatoid arthritis in China and Globally, 1990–2021. Items ASPR (per 100,000) AAPC (%) ASIR (per 100,000) AAPC (%) ASMR (per 100,000) AAPC (%) Age-standardized DALYs rate (per 100,000) AAPC (%) 1990 2021 1990 2021 1990 2021 1990 2021 Global 635.54 (551.56–735.50) 726.95 (634.09–834.85) 0.44* (0.41–0.46) 24.87 (15.88–35.30) 30.32 (19.83–42.38) 0.64* (0.62–0.67) 4.18 (3.60–4.74) 3.20 (2.58–3.71) –0.82* (–0.96––0.67) 150.85 (123.61–182.04) 143.22 (113.41–178.45) –0.16* (–0.21 to –1.63) Male 375.31 (319.40–442.91) 445.76 (383.93–519.79) 0.56* (0.54–0.58) 18.41 (11.80–26.00) 22.41 (14.76–31.02) 0.63* (0.61–0.66) 2.88 (2.12–3.39) 2.45 (1.58–2.98) –0.49* (–0.66––0.31) 95.34 (75.83–117.68) 95.16 (72.92–119.03) –0.02 (–0.12 to 0.08) Female 844.23 (736.43–969.81) 969.96 (849.93–1108.49 0.45* (0.43–0.48) 30.39 (19.39–43.20) 37.48 (24.42–52.57) 0.68* (0.65–0.71) 5.11 (4.41–5.86) 3.79 (3.08–4.56) –0.95* (–1.12––0.78) 194.80 (159.71–235.78) 184.58 (143.84–231.40) –0.17* (–0.27 to –0.07) China 646.92 (547.58–765.67) 748.41 (639.92–876.49) 0.47* (0.46–0.48) 22.79 (13.20–34.74) 29.59 (18.26–43.31) 0.85* (0.83–0.88) 4.51 (3.56–5.72) 3.81 (2.61–4.76) –0.52* (–1.02––0.01) 156.47 (125.02–197.37) 153.44 (117.65–194.88) –0.05 (–0.26 to 0.17) Male 449.46 (370.85–542.78) 544.77 (458.12–645.32) 0.62* (0.61–0.64) 21.15 (12.51–31.59) 28.08 (17.90–40.10) 0.92* (0.89–0.94) 3.75 (2.02–5.35) 3.77 (1.74–5.20) –0.04 (–0.31–0.24) 116.61 (83.65–154.49) 123.70 (86.94–160.29) 0.17* (0.03 to 0.30) Female 825.45 (702.05–971.80) 940.88 (811.42–1095.40) 0.43* (0.41–0.45) 24.52 (13.70–38.00) 31.42 (18.76–47.22) 0.81* (0.78–0.84) 5.15 (4.04–6.60) 3.98 (2.73–5.17) –0.79* (–1.25––0.32) 192.46 (152.84–242.73) 182.93 (136.90–234.77) –0.15* (–0.29 to –0.01) AAPC: Average annual percentage change; ASIR: Age standardised incidence rate; ASMR: Age standardised mortality rate; ASPR: Age standardised prevalence rate; DALYs: Disability-adjusted life years; *P <0.05. From 1990 to 2021, both the ASPR and ASIR among the elderly showed a consistent increase in China and globally. In contrast, ASMR and age-standardized DALYs rate declined steadily from 1990 to 1998, followed by a slight increase between 1998 and 2003, and then continued to decrease at the global level. In China, both indicators decreased from 1990 to 1996, rose sharply from 1996 to 2004, and then declined sharply again thereafter. [Supplementary Figure 2, https://links.lww.com/CM9/C624]. Notably, China exhibited higher average annual percent changes (AAPCs) values for ASPR (0.47% vs. 0.44%) and ASIR (0.85% vs. 0.64%) than the global average, but lower AAPCs values for ASMR (–0.52% vs. –0.82%) and age-standardized DALYs rate (–0.05% vs. –0.16%), indicating a relatively faster rise in prevalence and incidence but a slower decline in mortality and disease burden compared with global trends from 1990 to 2021 [Table 1]. Gender disparities in the RA burden among older adults were evident, with consistently higher rates in females than in males both globally and in China. Chinese males had higher ASPR, ASIR, and age-standardized DALYs rates than global males in both 1990 and 2021, while opposite results were identified in females. From 1990 to 2021, both ASPR and ASIR increased globally and in China for both sexes. In contrast, ASMR and age-standardized DALYs rate declined or remained stable in most population groups, with the exception of Chinese males, who experienced a notable increase in age-standardized DALYs rate [Table 1]. Projections based on both the BAPC model and the Norpred framework indicate that, by 2044, the ASPR and ASIR of RA among older adults will continue to rise, while ASMR and age-standardized DALYs rate are expected to decline globally and in China [Supplementary Figures 3 and 4, https://links.lww.com/CM9/C624]. According to the BAPC model, China is projected to maintain higher ASPR, ASMR, and age-standardized DALYs rate but lower ASIR compared to global levels. However, the Norpred model predicts that China’s ASIR will surpass the global level after 2022. Overall, both models predict a significant RA burden among the elderly in China in the coming years. For both sexes combined, as well as among males, the smoking-attributable mortality and DALYs rates among older adults with RA exhibited similar patterns between in China and the global population, although the global rates were consistently higher than those observed in China. Among males, the RA-related mortality rate attributable to smoking increased with age in both China and the global population, peaking slightly later in global males (90–94 years) than in Chinese males (85–89 years), followed by a modest decline. Similarly, the RA-related DALYs rates rose with age in both groups, showing an initial peak around 75–79 years, a subsequent decline, and a second peak at 90–94 years globally and 85–89 years in Chinese males, then decreasing. Among females, smoking-attributable RA mortality rates increased steadily with age in China and globally. In contrast, smoking-attributable RA DALYs rates among global females remained relatively stable across age groups. Although, smoking-attributable RA DALYs rate among females in China exhibited a decline with advancing age, they were higher than global female levels between the ages of 60 and 89 years, and dropped below the global level after the age of 90 [Supplementary Figure 5, https://links.lww.com/CM9/C624]. Compared to 1990, smoking-attributable RA mortality and DALYs rates among the elderly population in 2021 showed a decline in global population for both sexes and in Chinese females [Supplementary Figure 6, https://links.lww.com/CM9/C624]. In Chinese males, smoking-attributable RA mortality rates generally decreased or remained stable across most age groups, with increases observed among those aged older than 85 years. DALYs rates followed a similar pattern, with slight increases noted in individuals over age 80. From 1990 to 2021, ASPR and ASIR rose steadily in both China and globally, likely reflecting improved disease recognition and diagnostic capabilities, population aging, and longer life expectancy, which have facilitated earlier and more frequent RA diagnoses and prolonged survival. While ASMR and age standardised DALYs rates declined in both settings—likely due to advances in pharmacologic therapies, earlier intervention, and expanded access to specialist care—the slower decline in China compared with the global trend underscores persistent gaps in early diagnosis, continuity of care, and access to rheumatologic expertise, particularly among older adults. Addressing these disparities remains essential for improving outcomes and ensuring equitable care for the aging population in China. Projections to 2044 using the BAPC model—which accounts for age, period, and cohort effects—suggest that China will continue to experience higher ASPR, ASMR, and age standardised DALYs rates, but lower ASIR than global levels. Although the BAPC model effectively captures long-term and nonlinear temporal trends, its dependence on historical data and limited ability to reflect future policy developments or emerging risk factors may reduce forecasting precision. By contrast, the Norpred model—focused on recent trends and short-term projections—anticipates that the ASIR in China surpassed the global average around 2022. These differences highlight model-specific sensitivities to input data and temporal assumptions. Nevertheless, both models consistently forecast marked declines in ASMR and age standardised DALYs rates by 2044 in both China and globally—likely reflecting health system improvements and increased access to care. Continued, targeted public health strategies will be essential to sustain this progress and further reduce the burden of RA in aging populations. This study revealed a persistently higher RA burden among elderly females than males, both globally and in China. Biological differences in immune function and the immunomodulatory effects of estrogen may contribute to greater susceptibility and severity in women. Additionally, higher healthcare-seeking behavior may lead to increased diagnosis and reporting rates. In contrast, the elevated AAPC of age-standardised DALYs rates observed among Chinese males likely reflects a higher prevalence of smoking-related risk. Compared to 1990, smoking-attributable RA mortality and DALYs rates in 2021 declined across both sexes globally, reflecting the benefits of tobacco control and improved RA management. Similar reductions were observed in Chinese females; however, rates among Chinese males remained stable or declined only modestly, with notable increases in mortality among those aged over 85 and in DALYs among those over 80 years. These trends suggest that older Chinese males continue to face elevated risks, likely due to cumulative tobacco exposure, age-related vulnerability, and a lack of targeted interventions, contributing to the notable rise in age-standardized DALYs rates from 1990 to 2021. Notably, in 2021, Chinese females aged 60–89 years experienced higher smoking-attributable RA-related DALYs than the global average, despite age-related declines. Those concentrated burden highlight the need for age- and sex-specific strategies, such as early RA screening and smoking cessation support. In conclusion, this study reveals a substantial and growing burden of age-related RA, particularly in China. Although future projections indicate reductions in ASMR and age-standardised DALYs rates, persistent disparities—especially among elderly males over 80 and females aged 60–89 years in China—underscore the need for targeted interventions. Funding This study was supported by the National Key R&D Program of China (Nos. 2022YFC3602002 and 2022YFC3602000), Project Program of National Clinical Research Center for Geriatric Disorders (No. 2022LNJJ06), the National Natural Science Foundation of China (No. 82202002), and the Natural Science Foundation of Hunan Province, China (No. 2025JJ60502). No funding bodies had any role in the preparation of present manuscript. Conflicts of interest None.