Meteorological epidemiology of Parkinson's Disease

Papers such as that by Willis et al. [1] show that there are geographical differences in the prevalence of Parkinson's disease. In their analysis of US data, they show that there is a zone of low prevalence in the Rocky mountains and a zone of higher prevalence to the east of a line drawn between Texas and the Great Lakes.

Other work, see for instance the thread "Temporal Epidemiology" [2] shows an annual cycle in the number of deaths in the US where PD is a factor, with high numbers dying in the winter and lower numbers dying in the summer. Typically people die with PD rather than from PD, and even then after a long period of chronic illness. So it does not necessarily mean that the etiology of PD involves the same periodicity. Nevertheless, one can speculate that the recurrence of the conditions that set in motion the process that led to PD in the first place also hasten its increasing severity.

The obvious common denominator between spatial changes and annual changes is the weather.

There appears to be little work published in analysing the prevalence of Parkinson's either in terms of short term meteorological effects or longer term climatic effects. There is no suggestion that weather per se causes PD but, rather, that meterological conditions can modulate possible disease vectors.

Rick, to whom my thanks, started a thread [3] that asked whether temperature was a factor in PD.

There appears to be an association between the prevalence of PD in the US and the annual mean rainfall [4], with areas of higher rainfall having on average higher levels of PD.

Also, there is a striking association between the partition of the US into west (lower PD) and east (higher PD) parts and the position of a zone of mean surface level winds which are for much of the year southerly (that is, from the south to the north) [5] that starts in Texas and continues north towards the Canadian border.

There are many ways in which meteorology could play a role in the etiology of Parkinson's. These include:
- create the conditions for pathogens to thrive or to die. For instance, Science Daily reports [6] that "Two types of environmental conditions -- cold-dry and humid-rainy -- are associated with seasonal influenza epidemics".
- distribute toxins;
- wash-out toxins and pathogens suspended in the atmosphere.

If these areas were proven to be material in the etiology of Parkinson's, it would take us a step closer to being able to control the disease.

References

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

[2] http://neurotalk.psychcentral.com/sh...light=temporal

[3] http://neurotalk.psychcentral.com/sh...hlight=climate

[4] "Precipitation: Annual Climatology (1981-2010)"
Natural Resources Conservation Service
http://www.wcc.nrcs.usda.gov/climate/prism.html

[5] "CLIMATOLOGICAL MEAN AND INTERANNUAL VARIANCE OF UNITED STATES SURFACE WIND SPEED, DIRECTION AND VELOCITY"
KATHERINE KLINK
Int. J. Climatol. 19: 471–488 (1999)
http://www.researchgate.net/...mean...._IJOC_1999.pdf

[6] "New Light Shed On Role of Climate in Influenza Transmission"
Science Daily, Mar. 7, 2013
http://www.sciencedaily.com/releases...0307190635.htm

John