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August 16, 2006

Mediators of the Association Between Mortality Risk and Socioeconomic Status—Reply

JAMA. 2006;296(7):763-764. doi:10.1001/jama.296.7.764-a

In Reply: We agree with Dr Hamer that public initiatives that address physical fitness and autonomic function are essential interventions that potentially could narrow socioeconomic disparities in cardiovascular health outcomes. We commend the National Health Service (Great Britain) life check for taking a leading role.

Dr Brotman raises an important concern about the stability of the formula used in quantifying the relative contribution of functional capacity and heart rate recovery in our study. Although the formula has been cited in numerous epidemiologic and clinical sources,1-3 we agree that it is problematic. Hazard ratios and odd ratios are derived by exponentiating model parameter coefficients. They center around 1.0 in a necessarily asymmetric way—on the “positive” end, relative risks approach infinity but on the “negative” end, relative risk can never be less than zero. In contrast, parameter coefficients (typically called β) are part of a logarithmic linear (or polynomial) equation and center around 0.0. They are symmetric in that their potential values range from negative infinity to positive infinity.