The Johnston County Osteoarthritis Project: Arthritis & Disability

Funding Number: DP16-003

Project Description

The Johnson County Osteoarthritis Project is a unique, community-based, longitudinal study of approximately 3,200 rural white and African American residents aged 45 years or conducted by the Thurston Arthritis Research Center (TARC) at the University of North Carolina (UNC) School of Medicine. The Centers for Disease Control and Prevention (CDC) has been the primary funding agency for this project since it began in 1991.
TARC originally designed this project to determine racial differences in the prevalence, incidence, and risk factors associated with the occurrence and progression of hip and knee osteoarthritis (OA)—the most common and disabling types of arthritis. Results of the project are creating a better understanding of how and why these conditions occur and what modifiable risk factors can be targeted to reduce their effect. This project implements surveillance and epidemiology strategies from the National Arthritis Action Plan—A Public Health Strategy, which are a priority for the CDC Arthritis Program.
CDC’s initial support was by CDC’s National Center for Environmental Health’s Office of Disability and Health, but has come from CDC’s Arthritis Program since 1999.  The project receives additional support from non-CDC organizations, including the National Institutes of Health (National Institute of Arthritis and Musculoskeletal and Skin Diseases, the National Institute of Mental Health) and a wide variety of other sources. You can learn more about the project at the Johnson County Osteoarthritis Project page on the UNC School of Medicine Website.

Initial Project Objectives

Goals of the Johnston County Osteoarthritis Project are to

• Determine the prevalence, incidence, and risk factors associated with the occurrence and progression of hip and knee osteoarthritis.
• Determine racial or ethnic differences in outcome and in the effect of risk factors upon OA outcomes.

Key Findings

Time 0 (T0, Baseline) (1991–1998)

From 1991 to 1998, participants aged 45 years or older were enrolled in the project. Analyses published from this phase of the project demonstrated

• A higher rate of OA among African Americans than previously thought.
• The importance of overweight in the development and severity of OA among African Americans, particularly women.
• The importance of pain in determining functional limitations among people with OA.
• The high prevalence of four different measures of knee osteoarthritis: knee symptoms, modest and severe radiographic OA, and symptomatic knee OA.

As the only study of OA biomarkers to include African Americans, the project has been pivotal in this burgeoning field, and demonstrated that

• Ethnic differences exist in multiple OA biomarkers.
• Some serum biomarkers may predict pre-radiographic OA.
• Body mass index, comorbid conditions, and medications can confound associations between some biomarkers and OA.
• Hormone replacement therapy (HRT) is associated with lower levels of several OA biomarkers, elucidating potential mechanisms behind the effect of HRT and OA.
• OA should be accounted for in relationships between C-Reactive Protein and cardiovascular disease.

The project also examined serum antioxidants as risk factors for OA and noted that higher levels of serum lutein, beta-cryptoxanthin, and the ratio of alpha to gamma tocopherol were associated with lower odds of having knee osteoarthritis. The project was also the only human study examining metabolomics in OA, showing distinct urinary metabolite patterns that can distinguish those with OA from controls.
 

Time 1 (T1, First Follow-up) (1999–2004)

Analyses published from this phase of the project demonstrated

• A higher rate of progression of OA among African Americans than previously thought.
• The importance of overweight in OA among African American women, and the contributions of body composition and fat distribution in this relationship.
• Higher odds of radiographic OA presence and severity in those with low levels of (toenail) selenium, a new and potentially modifiable risk factor for OA.
• Nearly 1 in 2 adults may develop symptomatic knee OA by age 85 years.
  • About 2 in 3 people who are obese may develop symptomatic knee OA in their lifetime.
• About 1 in 4 people may develop painful hip arthritis in their lifetime.
  

Time 2 (T2, Second Follow-up) (2005–2010)

Analyses from this phase of the project are examining disability, function, mortality, racial differences in radiographic evidence of disease, racial differences in willingness to undergo total joint replacement, and the effects of socioeconomic status on arthritis outcomes.  
 

Time 3 (T3, Third Follow-up) (2011–2016)

Data collection for this phase is finishing, and analyses will begin soon.
 

Time 4 (T4, Fourth Follow-up; new general chronic disease expansion)

Data collection for T4 will begin in 2017. New funding is allowing the project to expand to address interactions of arthritis and other chronic conditions (e.g., diabetes), a younger population (aged 35 years and older), and new groups (Hispanics). Addressing multiple chronic conditions is a research approach that is more realistic and relevant to public health and allows better analyses and understandings of how chronic conditions interact and what outcomes they produce. 

Publications and Abstracts

View related publications and abstracts here.

Read more about the Johnston County Osteoarthritis Project in University of North Carolina’s Thurston Arthritis Research Center newsletter, Thurston Today.

Principal Investigator

Joanne M. Jordan, MD, MPH
Thurston Arthritis Research Center
3300 Doc J. Thurston, Jr. Building
CB#7280
University of North Carolina
Chapel Hill, NC 27599-7280

Back to CDC-Funded Science