Osteoarthritis is the most common type of arthritis, which usually affects multiple joints. According to findings reported today in Arthritis & Rheumatism, a peer-reviewed journal of the American College of Rheumatology (ACR), new research suggests that African Americans have a higher prevalence of multiple, large-joint osteoarthritis (OA), which may not be recognized based on the current definition of “generalized OA.” The study, conducted by part of the Johnston County Osteoarthritis Project, Dr. Amanda Nelson from the University of North Carolina at the Chapel Hill-UNC Rheumatology/Thurston Arthritis Research Center and colleagues, also shows that compared to Caucasians, African Americans are at greater risk to develop OA in the knee joint but are less likely to be affected by OA in the hand.

According to estimations of The National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) over 27 million adults aged 25 years and older, are suffering from OA. NIAMS projections show that by 2030, 67 million people will be diagnosed with arthritis based on the fact that OA occurrence increases with population age. Although earlier studies have examined radiographic or symptomatic OA patterns using combinations of different joint sites, multi-joint involvement research has mainly been limited to Caucasian women.

The study, evaluated radiographic data for the hands, knee (tibofemoral [TFJ] and patellofemoral joints), hips and spine (lumbosacral) in African American and Caucasian men and women aged 45 years and older. Researchers obtained age, gender, race and body mass index (BMI) data by using questionnaires and clinical examination. The average age of the study participants was 65 years or older, with an average BMI classed as ‘obese’. A third of the participants were male and two thirds were Caucasian.

According to the evaluation researchers identified 16 mutually exclusive hand OA phenotypes in 2,083 participants and 32 whole-body phenotypes in 1,419 individuals.

After taking into account participants’ age, gender and BMI, researchers discovered that compared with Caucasians, African Americans had substantially less frequent OA in the joints of the fingertip (distal interphalangeal), either just in the finger tips or also in other joints of the hand. African Americans were also potentially at double the risk of having osteoarthritis in their knee (TFJ) compared with Caucasians and had a 77% greater likelihood of having OA in both their knee and spine. Both races showed similar frequencies of OA occurrence in joints of the hand excluding distal interphalangeal joints.

In total, 42% of the participants suffered from OA in the knee, whilst 36% suffered from osteoarthritis in the hip and 32% in the hand. The most common form of OA was detected in the spine in 62% of the participants.

In a concluding statement Dr. Nelson says:

“Racial differences in OA phenotypes were more significant than gender disparity. Our findings suggest a substantial health burden of large-joint OA, particularly hip and spine, among African Americans and further studies that address this concern are warranted.”

Written by Petra Rattue