Low-Income Patients Have Better Outcome from Knee Replacement
Contrary to previous reports of the association between income and patient outcome, patients who have an annual income of less than $35,000 report better outcomes after knee arthroplasty than those who make more.
-- by Nina Lincoff
Medical research is dynamic. It changes with every breakthrough and follows a fluctuating population. And sometimes, it can be counterintuitive. Researchers from the Mayo Clinic in Minnesota and the University of Alabama at Birmingham have reported just such a paradox. Going against past research that found that patients in lower socioeconomic levels experience less positive patient outcome after knee arthroplasty, or knee replacement surgery, a new study reports that those whose make less than $35,000 annually actually experience better patient outcome.
While the reasons behind these findings are unknown, it is proof that blanket assumptions very rarely hold true.
The Expert Take
“While some research exists with regards to effect of socioeconomic status on medical complications after joint replacement, less has been reported related to patient-reported outcomes," said study author Jasvinder Singh, M.D. "This study begins to fill this knowledge gap."
The question researchers were trying to answer, said study author David Lewallen, M.D. from the Mayo Clinic in an email to Healthline, is what the cause is for reported worse patient outcome for those from lower income brackets. “It’s important to understand that we’re talking about associations here, not causal relationships,” said Lewallen. In turn, a low socioeconomic status doesn’t necessarily cause poor outcome, but may be associated with other factors that affect outcome. So it may be a tag, or marker, for potential problems.
When these other factors were accounted for in study of patients that had undergone knee arthroplasty, it turns out that income didn’t necessarily predicate a better outcome. As it turns out, said Lewallen, “the low-income patients in this study didn’t do worse. In fact, they did somewhat better at a couple of time intervals."
Outside of patient income, these results mostly speak to the efficacy of the procedure. “This operation really works and it improves the status of people a great deal," said Lewallen. "It helps their function, it gets rid of their pain."
Source and Method
Researchers used data from the Mayo Clinic Total Joint Registry to compare income with knee improvement and pain reports after arthroplasty. Data from over 7,000 patients was examined after two years, and data from just over 4,000 was examined after five years. In both groups, the lower income pool had better patient outcome than those in higher income brackets.
Low income patients are reporting better patient outcome. This is, said Lewallen, perhaps because they wait longer to have knee arthroplasty and thus feel a greater relief of pain. These results really speak to the effectiveness of the operation. “If you’re in a group of patients who, for whatever reason, present later with more severe involvement, you will get a big improvement,” said Lewallen.
Risk factors that predict poor patient outcome were examined by Health Services Research in regards to hip replacement surgery. Race, education, age, sex, and marital status were all found to be factors that affected patient outcome.