Originally Posted by johnt

To my eyes, the key feature of these maps is the under representation of Parkinson's in the west coast and Rocky Mountain states and an over representation in a band from the Texas coast north eastwards to the Canadian border. In particular, areas close to the Mississippi and Ohio rivers seem to have high incidence.

I've searched the internet for any form of data which has a similar distribution. (I don't have access to the raw PD data, so I've not been able to use statistical techniques. My approach has been to simply "eye-ball" the maps.)

I've posted on apparent correlations (which may or may not be causal) between PD and:
- surface ozone [2];
- atmospheric nitric oxide [2];
- air quality [3].

I've now extended my search to look for biological entities with similar distributions to PD. One that has jumped out is the fungus histoplasma capsulatum, which causes a disease called histoplasmosis.

The correlation between PD and histoplasmosis is far from perfect. For instance South Dakota is high for histoplasmosis, but low for PD. Also, histoplasmosis is rare in areas further than 45 degrees from the equator, so it is unlikely to play a large role in PD in, for instance, the UK.

Given the above evidence, albeit circumstantial, it seems to me that histoplasma capsulatum could possibly be a cause of some cases of Parkinson's. If so, anti-fungals might help some people.

John