Interrelationships of Sex, Physician-Diagnosed Arthritis, Chronic Inflammation, and Physical Functioning in the Third National Health and Nutrition Examination Surveys

Objective: To examine whether serum concentrations of C-reactive protein (CRP) and fibrinogen were associated with total score on a validated 12-item physical functioning scale and whether the magnitude and direction of these associations differed according to sex and physician-diagnosed arthritis. Method: Secondary analyses of cross-sectional data from the Third National Health and Nutrition Examination Survey were conducted using a representative sample of 4,606 older adults, 60 years and older. Results: Linear models suggested that overall physical functioning was strongly and independently associated with CRP (adjusted β = +.68, 95% confidence interval [CI] = [+0.42, +0.94]) and fibrinogen (adjusted β = +1.66, 95% CI = [+0.89, +2.42]); these associations were modified by physician-diagnosed arthritis status, with strongest associations observed among individuals diagnosed with rheumatoid arthritis or no arthritis and weakest association observed among those diagnosed with osteoarthritis. Conclusion: CRP and fibrinogen may be associated with poorer physical functioning in older adults, especially among those having rheumatoid arthritis or no arthritis.