Sometimes I just pause to marvel at the power and, yes, beauty of social science.
From long experience and careful evaluation, we have come to learn that one simple, completely subjective question produces answers with amazing predictive power.
The question is:
Would you say your health in general is excellent, very good, good, fair, or poor?
There may be one, but I’m not aware of a more accurate or reliable predictor of mortality that can be ascertained in so few words. This “self-rated health” question is one of the most widely used survey items when the goal is to minimize cost and invasiveness. It doesn’t work with every individual, of course, but if you get 1,000 people to answer this question, and then check up on them five years later, you’ll see what I mean.
One review article on the effect of self-rated health on mortality, by Ellen Idler and Yael Benyamini, is the fifth-most cited article in the history of the Journal of Health and Social Behavior (1,740 citations as of yesterday). They showed that, in most studies, the question (or something close to it) predicts mortality quite well even when other basic demographic factors are controlled statistically.
For those interested in inequality, this has become a useful way of assessing health inequality in various contexts and an indicator of population health across groups. Today’s case in point is from the 2009 National Health Interview Survey, which features a beautiful example of the health-social class gradient (which I’ve written about before).
(In this case, the question was asked about family members age>24 with whom the respondent lived, and adjusted for age differences across the education groups.)
Those gradients are very steep: from 38% of the high school dropouts with “excellent or very good” health to 74% of those with BAs or more. At the other end the ratio of dropout-to-BA percentages with “fair or poor” health is 4-to-1.
Part of what I love about this is the use of subjective assessments to measure a hard reality. We could draw blood, take blood pressure measurements or DNA, do CT scans and fitness tests. Or we can just ask, effectively, “how’s your health?”
Social scientists do a lot of fancy science (not that there’s anything wrong with that). This isn’t fancy science, just a simple, useful question based on a lot of previous research. And in this case it wasn’t cheap – this was a sample of about 34,000 households, reflecting a response rate of 82%. But it is good science, and that’s a sight to see — even when the news isn’t good.