Surrogate indicators in medicine are measures that might be correlated with physical health. An example would be cholesterol levels, which can be correlated with heart disease. There are general problems with such indicators: correlation does not imply causation; the correlation anyway may be weak; or the measure might indicate a specific medical concern but not the overall health of an individual. In recent years (here and here, for instance) I've inveighed against the medical establishment's use of surrogate indicators for policy purposes, claiming that most medical professionals have neither the incentive nor capacity to look at the broad health of a nation and to target that for improvement.
It's been a lonely road, so I was much cheered to hear this British Medical Journal podcast, with Professor Emeritus of Surgery, Michael Baum, arguing on exactly the same lines as I do in my work on applying the Social Policy Bond concept to health. There is a link to the BMJ article on which the podcast is based here. My paper on Health Bonds, and links to some of my other blog posts on the subject can be found here.