The influence of income and race on total knee arthroplasty in the United States.
BACKGROUND
The associations among income, total knee arthroplasty, and underlying rates of knee osteoarthritis are not well understood. We studied whether high-income Medicare recipients are more likely to have a knee arthroplasty and less likely to suffer from knee osteoarthritis.


METHODS
Two data sources were used: (1) the 2000 United States Medicare claims data measuring the incidence of total knee arthroplasty by race, ethnicity, zip (postal) code income, and region (n = 27.5 million) and (2) the National Health and Nutrition Examination Survey (NHANES III) for individuals with an age of sixty years or more (n = 1926) with radiographic and clinical evidence of osteoarthritis. Logistic regression methods were used to adjust for covariates.


RESULTS
At the national level, age-adjusted rates of total knee arthroplasty in the high-income quintile were no higher than those in the low-income group (odds ratio, 0.98; 95% confidence interval, 0.96 to 1.00). Within regions, access to care was better for high-income groups (odds ratio, 1.19; 95% confidence interval, 1.17 to 1.22). Racial disparities in arthroplasty were significant (p < 0.001); the odds ratio was 0.36 (95% confidence interval, 0.34 to 0.38) for black men and 0.45 (95% confidence interval, 0.41 to 0.49) for Asian women. There was no evidence of an income gradient for most clinical and radiographic measures of arthritis. The exception was a significant negative association between income and pain on passive motion (p < 0.05).


CONCLUSIONS
High-income Medicare enrollees are no less likely to have osteoarthritis than low-income enrollees but have somewhat better access to care. Racial disparities are more important than those that are attributable to socioeconomic status.
Skinner
Jonathan
J
Center for Evaluative Clinical Sciences, HB 7152 Dartmouth Medical School, Hanover, NH 03755, USA. jon.skinner@dartmouth.edu
Zhou
Weiping
W
Weinstein
James
J
D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000706:statistics & numerical data*; D005006:Ethnicity / Q000706:statistics & numerical data*; D005260:Female; D006297:Health Services Accessibility; D006801:Humans; D007182:Income; D008297:Male; D006278:Medicare; D009749:Nutrition Surveys; D020370:Osteoarthritis, Knee / Q000208:ethnology* / Q000601:surgery; D017678:Sex Distribution; D014481:United States / Q000453:epidemiology; D044465:White People / Q000706:statistics & numerical data*