Disparities, Worsening Inequality of Growing RA Burden, Reveals AI-Driven Study

Since 1980, the global prevalence of rheumatoid arthritis (RA) has risen sharply, with incidence growing 13.2% over 3 decades from 1990 to 2021, according to a study published today in Annals of the Rheumatic Diseases.¹ In addition, there are significant regional disparities and a shifting age profile.

The analysis also modeled how and where the RA burden will grow through 2040, using artificial intelligence (AI) to examine prevalence, incidence, mortality, years of lost life, and disability across 953 distinct locations worldwide.^1,2

Although individuals over age 55 still account for most of those with RA, investigators found trends that show the condition is affecting more young adults. Distribution of the RA burden is localized and complex, hitting hardest in relatively wealthy countries but in a highly uneven way.

"...after 2015, the age of onset of RA showed a trend towards younger age groups, with an increasing proportion of patients aged 20 to 54, especially in high SDI [sociodemographic index] areas," the authors wrote.

The analysis covered the years 1980 through 2021 and showed that while the standardized death rate from RA fell by 32.7% over that period, disability burdens increased, with increased effects largely seen in countries with middle and high socioeconomic status. However, there are important wrinkles in the data that merit further study: of note, the disability burden of RA is falling in Japan, a high-income country. Study authors speculate that early detection programs and the country’s diet of less inflammatory foods may account for this.

Study authors, all of whom are from China, note that data confirm the relationship between tobacco use and RA and suggest that efforts to reduce China’s high smoking rates could reduce that country’s burden.

The study’s principal investigator and senior author, Queran Lin, MPH, of the World Health Organization (WHO) Collaborating Centre for Public Health Education and Training, outlined in a statement how the study’s localized findings—and identification of “hotspots”—add to the knowledge base on RA.²

“While previous Global Burden of Disease (GBD) studies have provided important insights, they have largely focused on high-level descriptions and visualizations at global and national scales, failing to capture local disparities or the dynamic interactions between socioeconomic development and disease trends,” Lin, who also holds appointments at Imperial College London and Sun Yat-Sen Memorial Hospital, Guangzhou, said in a statement.²

Use of advanced analytical tools allowed the Global-to-Local Burden of Disease Collaboration to unlock the full potential of the GBD dataset, which was pioneered by the Institute for Health Metrics and Evaluation, University of Washington, Lin said. “We were able to generate the most granular disease burden estimates to date, offering a new framework for guiding precision public health across diverse populations.”

Globally, the study found significant absolute and relative inequalities based on each country’s SDI, with a disproportionately higher burden shouldered by countries with high and high-middle SDI.

Within the Overall RA Rise, “Hotspots” Identified

In 2021, RA affected 17.9 million people worldwide, with disease burden generally higher in Western Europe and North America and lower in African countries. Among 204 countries and territories, Ireland had the highest standardized incidence rate, at 35.1/100,000 in 2021, with a 22.5% increase compared with 1990.¹

Among other Global North countries, Finland, the United Kingdom, Norway, and Canada had relatively high rates of RA burden. Elsewhere, “hotspots” were found in the mountainous regions of Mexico and Peru. Among localities, the analysis identified West Berkshire in the United Kingdom as having the highest incidence rate of 35.1/100,000 and Zacatecas, Mexico, as having the highest disability-adjusted life year (DALY) rate of 112.6/100,000.

In the United States, the highest RA burden is seen in states of the Mountain West, with Montana having the highest absolute incidence.

Widening Inequalities

DALY-related inequality has increased 62.55% since 1990, with Finland, Ireland, and New Zealand as the most unequal countries in 2021. Because RA burden is more likely to be high in countries with higher SDI, the gap between the best possible outcomes for an area’s health infrastructure and actual outcomes continues to grow; the authors say this indicates “the burden of rheumatoid arthritis has been severely neglected.”

Measured by the slope index of inequality, global incidence inequality increased by more than 60% and DALY-related inequality by more than 62% since 1990, with Finland, Ireland, and New Zealand ranking as the most unequal.

Diet may be a factor

The authors contrasted outcomes between the United Kingdom and Japan, which they note are both island nations of similar geography, income, and types of employment. DALY in the United Kingdom is rising, while Japan is the single high-income country where it is falling. According to a statement, “Japan’s declining DALY rates despite high SDI may reflect nationwide early diagnosis programs, widespread use of biologic therapies, and a diet rich in anti-inflammatory components.”

RA Burden to Rise Through 2040

Using the iTransformer model, researchers forecast that RA incidence will continue to climb globally through 2040, especially in low– and middle-SDI countries. Assuming access to interventions improves, DALY rates are projected to fall in high-income regions but will likely rise in aging and underserved populations.

The authors state that the findings highlight the need for better policy solutions to identifying and addressing RA. Trends seen in high-SDI countries are forecast to reach low- and middle-SDI areas by 2040. By 2040, low-middle SDI regions may see increasing DALYs due to an aging population.

“The adoption of this advanced framework quantifies the expected impact of feasible intervention scenarios in public health, supplying policymakers at global, national, and local levels with more reliable, dynamic evidence, redefining the very paradigm of health surveillance,” said co-lead author Wenyi Jin, MD, PhD, who holds appointments at Renmin Hospital of Wuhan University and the City University of Hong Kong.²

However, global resources to address RA burden are uneven. Many countries or regions are not supporting data gathering needed to target policy interventions, the authors say.

“Population growth and ageing are key drivers of the global burden of RA, particularly in rapidly ageing regions such as East and South Asia,” the authors explained. “Countries such as Thailand and China must prioritise geriatric care and early RA management, while nations such as Pakistan and India need expanded healthcare infrastructure to address population-driven increases.”

They also highlighted smoking cessation as a high-impact intervention. In China, for example, implementing robust tobacco control policies could reduce RA-related deaths by 16.8% and DALYs by 20.6% among male patients.

Beyond dietary adjustments, the authors recommended global adoption of precision health policies, including RA screening in primary care, expanded access to biologics, and tailored interventions at the subnational level. They also caution against overreliance on GDP-based metrics for public health planning, emphasizing that more granular, localized data is necessary for equitable resource allocation.

“Addressing the multifactorial nature of RA demands global collaboration and tailored strategies to mitigate its growing public health impact,” the authors wrote.

References

1. Jin W, Wang Q, Jin C, et al. Spatiotemporal distributions and regional disparities of rheumatoid arthritis in 953 global to local locations, 1980-2040, with deep learning-empowered forecasts and evaluation of interventional policies' benefits. Ann Rheum Dis. Published online June 16, 2025. DOI: 10.1016/j.ard.2025.04.009 /
2. AI-powered study shows surge in global rheumatoid arthritis since 1980, revealing local hotspots. News release. EurekaAlert. June 15, 2025. Accessed June 16, 2025. https://www.eurekalert.org/multimedia/1077050