Could I answer the question in a similar way but with a different perspective? All day long I work in a research centre that focuses on what determines the health of populations. In most cases it's a combination of a number of factors, so we have to look at biological factors such as the status of your immune system, genetic susceptibility, the environment within which you live, your occupation, social behaviour, what access you have to health services. Lifestyles serve as factors. All these factors typically interact to determine whether you might demonstrate an adverse health outcome, and trying to disentangle them and understand those interactions is my job, not just for Parkinson's but for a whole host of diseases.
That's the general answer, I think, to why we don't see the same thing everywhere. It's because of these complex interactions among a wide range of health determinants.
Did we say the same thing, Ted?