socertese writes: "once pd biomarkers are identified and inexpensive tests developed, the environmental causes should be much easier to identify since you will be able to measure progression on a huge population on even a weekly schedule. and test diet's affect on pd. and find disease slowing drugs."

That can be done now by:
http://www.parkinsonsmeasurement.org/PDMeasure/

Although better markers are likely to be found by the ongoing research, there's no need to wait, 1, 2, or whatever, years before collecting data. You can start now. There are a number of simple measures that correlate with PD. The one I'm most familiar with is the side to side tapping test. This can be measured on the computer and the results sent to a database. It's not just inexpensive, it's free. It can be measured hourly or better. What's needed is for PwP to donate their data.

Garcia-Ruiz et al. [1] write: "All CAPIT timed tests, especially tapping, maintained an excellent correlation with UPDRS in both off and on state. Tapping seems to be the best CAPIT timed test for objective motor evaluation of PD." Our side to side test is similar to their "tapping" test.

A study investigating the relationship between sugar and PD would be a good one for us to look at.

On the information to hand now, I compared US, county level prevalence maps for:
- diabetes [2]
- obesity [2]
- Parkinson's [3]

It's a pity we don't have the raw data. Without it we can't do a proper analysis. But, "eye-balling" the maps, it looks, to me, like there's a correlation between these other conditions and PD. They are correlated with sugar consumption, so the suspicion is that PD is too. (As a technical point, one needs to be careful: correlation is not "transitive". In certain conditions, A can be positively correlated with B, B with C, but not A with C.)

I see the aetiology of Parkinson's in the following way: genetics sets a bar, high for some, low for others; aging lowers the bar. Eventually, provided something else doesn't get you first, lifestyle, environmental and biological toxins and illness aggregate to take you over the bar, where auto-immune responses accelerate the effect.

If this model is correct, if only we knew what they were, we can do something to slow the progression of PD, even in advanced cases. For instance, a question I would like answering is:

What effect on the rate of progression of my PD would a strict sugar free diet make?

As it is, I find sweet things sometimes reduce the symptoms of PD slightly.

References:

[1] "The usefulness of timed motor tests in assessing Parkinson's disease"
García-Ruiz PJ, Sánchez-Bernardos V, Cabo-López L
Revista de Neurologia [2009, 48(12):617-619]
http://europepmc.org/abstract/MED/19507119

[2] "Estimated County-Level Prevalence of Diabetes and Obesity --- United States, 2007"
CDC
http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5845a2.htm

[3] "Geographic and Ethnic Variation in Parkinson Disease: A Population-Based Study of US Medicare Beneficiaries"
Allison Wright Willis,a,* Bradley A. Evanoff,b Min Lian,b Susan R. Criswell,a and Brad A. Racette
Neuroepidemiology. 2010 April; 34(3): 143–151
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2865395/

John