Cigarette smoking and Parkinson disease: the illusion of a neuroprotective effect

Repeated studies have demonstrated a negative association between cigarette smoking and Parkinson disease. This negative association has led many investigators to suggest that some facet of cigarette smoking exerts a neuroprotective influence with respect to developing Parkinson disease. Longitudinal Gompertzian analysis demonstrates that no neuroprotective influence is necessary to account for the negative association between Parkinson disease and cigarette smoking. Indeed, the only assumption that needs to be made is that smokers experience earlier mortality than nonsmokers. The example of cigarette smoking and Parkinson disease illustrates a limitation with current risk factor analysis, i.e., disease patterns are typically interpreted using only two dimensions: genetics and the environment. However, longitudinal Gompertzian analysis demonstrates that disease mortality patterns and trends are actually three-dimensional phenomenon, with competition being the third dimension.