Prevalence, Progression, Symptoms: what's good for one may not be good for the others.

For instance, there's good epidemiological evidence that smoking reduces the chance of getting PD. But that does not, of itself, mean that smoking slows progression or reduces symptoms for someone diagnosed with PD.

Or, for another example, taking levodopa lessons my symptoms, but its impact on my progression is unclear.

How does this affect us?

Well, probably most of us on this forum are more interested in progression and symptoms, rather than etiology, per se. But, it seems to me, that most of the research is to do with etiology.

I'm not, here at least, interested in the ethics of this distribution. I am interested in how we use etiological data as evidence for the impact on progression and symptoms.

Does anyone have any examples of risk factors or therapies that are good/bad for prevalence while having the opposite effect on progression or symptoms?

John