Is there any correlation between Essential Tremor & population density?

*We know stress increases ET symptoms

* Experiments with lab rats/mice show greater aggression and stress indicators in high density populations. 
* Observation of human populations show similar traits. 
* Repeated stress can enhance long-term ET. 
– Is there a greater incident of ET, per 100,000 of population, in urban environments vs rural?
– Is there a means to measure this?
– Since survival mechanisms can be genetically passed on, is it possible that repeated stress triggering ET will increase probability of future generations with ET?
– Again:  Is ET an offset survival coping mechanism (reaction time / intuitive capability / shutdown – not reacting) to deal with repeated high stress situations that don’t allow immediate physical responses?