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I have a new working paper out with @ermeara and Susan Stewart. I learned a lot from it, so I thought I would share. Warning: Geeking to come. https://www.nber.org/papers/w27974?utm_campaign=ntwh&utm_medium=email&utm_source=ntwg6
The question we look at is education differences in pain, specifically in the knee. Why the knee? Musculoskeletal pain differs a lot by education; knee pain is the most affected joint; pain is a huge source of DI claims; and we have good measures of knee anatomy.
As shown here, knee pain differs by 5-10 percentage points between those with a college degree and those without.
This difference arose around the late 1970s and has been relatively stable since, even as overall knee pain has increased.
We first look at x-rays of knees. Do people with fewer years of education have knees with more arthritis? Surprisingly, the answer is no. rather, knees hurt more given the level of arthritis.
We look at four specific hypotheses for this: (1) obesity; (2) physical requirements on the job; (3) psychological factors (mood disorders, etc.); (4) medical treatment differences.
There is a clear link between knee pain and obesity (esp. BMI at maximum weight) and working in a more physically demanding job over one’s life.
And those two interact: being in a physically demanding job matters more for people who are obese.
We find no evidence that depressed mood or other psychological attributes affect the onset of knee pain. Nor do we find evidence that treatment differences explain knee pain.
Our conclusion is that the interaction of obesity and working in physically demanding jobs explains the gradient in pain.
One fun (?) side point: we looked at whether physiological responses to stimuli differ across groups. Specifically, does blood pressure increase more in response to stressful situations for people sorted by education? It does not.
Unfortunately, these results suggest that differences in pain by education will increase over time. We are creating more demanding jobs (physical care aide, home health aide) than we are eliminating them (secretaries).
