Getting to the Heart of Racial Disparities in OA

How do overall health and socioeconomic factors relate to racial disparities in incidence rates for knee osteoarthritis (OA)?

Attempting to delve into the nuances, a team from the Louisiana State University (LSU) Health Sciences Center in New Orleans designed a study which collected data from a prospective cross-sectional sample of adults who’d been treated with primary total knee arthroplasty (TKA), by a single surgeon, at a university-based, safety-net hospital from 2015 to 2019.

Their work, “Quantifying Mediators of Racial Disparities in Knee Osteoarthritis Outcome Scores,” was published in the July-September 2021 edition of JBJS Open Access.

The researchers prospectively enrolled 223 patients, all of whom self-reported as African American/Black or White (40.3% Black and 59.7% White).

The Well-Being Officer for the LSU Department of Orthopaedics, Jennifer Simkin, Ph.D., a co-author on this work, told OTW, “Health disparities contribute to rising medical costs and loss of people to our workforces. Osteoarthritis, specifically, is one of the leading causes of physical disability in the United States, and for Black Americans, osteoarthritis is more often associated with high pain and joint stiffness than for white Americans.”

“This means that Black Americans are more likely to experience loss of work and loss of ability to perform everyday duties due to osteoarthritis limitations. This study was designed to identify health, socioeconomic and demographic variables that mediate the disparity in pain so that we can start designing better interventions to eliminate this disparity.”

The researchers used the Knee Injury and Osteoarthritis Outcome Score (KOOS), which consists of 42 items (5 subscales): pain, other symptoms, activities of daily living, function in sport and recreation, and knee-related quality of life. They also collected patient surveys on demographic and health-behavior regarding ethnicity, race, sex, education level, marital status, and income level.

“Black patients had worse KOOS (Knee Injury and Osteoarthritis Outcome Score) pain, symptoms, and activities of daily living subscale scores than White patients,” wrote the authors. “In our cohort, Black patients were younger, more likely to be female, and more likely to report lower educational status. We identified age, sex, Charlson Comorbidity Index, and education as partial mediators of racial disparities in KOOS (Knee Injury and Osteoarthritis Outcome Score) subscale scores.”

“Insurance status, deformity, radiographic (Kellgren-Lawrence) grade, C-reactive protein level, marital status, body mass index, and income did not show mediating effects.”

“We found that, if age and sex were equal in both cohorts, the racial disparity in KOOS [Knee Injury and Osteoarthritis Outcome Score] symptom scores would be reduced by 20.7% and 9.1%, respectively (25.1% to 47% and 25.5% to 26.3%).”

“For KOOS (Knee Injury and Osteoarthritis Outcome Score) pain scores, age and education level explained 18.9% and 5.1% of the racial disparity (20.6% to 37% and 210.8% to 22.9%). Finally, for KOOS (Knee Injury and Osteoarthritis Outcome Score) activities of daily living scores, education level explained 3.2% of the disparity (219.4% to 26.6%).”

Answers…and More Questions

“Of the factors we analyzed,” said Dr. Simkin to OTW, “no single factor can explain the disparity in osteoarthritis pain. Several factors together, like age at time of total knee replacement (younger is worse pain) and number of co-morbidities can partially explain the disparities in pain reports. These factors should be considered when building new risk adjustment models. This study highlights the complexity behind racial disparities in health care and the need to: 1) think more creatively about solutions and 2) work toward more systemic changes.”

“Without proper intervention for patients with OA with a high level of pain, we risk continued rising health-care costs and loss to our workforces.”

“For decades, studies have shown that symptomatic OA is more prevalent in the population of Black Americans. Therefore, interventions to reduce pain and osteoarthritis symptoms specifically in Black populations would have a greater impact on reducing health-care costs. Where to start targeting interventions is not well defined. This study highlights the complexity of factors that mediate pain and symptoms in knee OA and provides evidence that mediation analysis can pinpoint primary areas for intervention.”