PD mortality rates, England and Wales, 1855-2004

Is there any evidence that the underlying prevalence of PD has increased over the last 150 years?

I cannot find any.

By underlying prevalence I mean the number of PwP taking into account changes in reporting conventions and practices, increasing population size, changes in the age distribution, the effects of drugs keeping people alive longer.

PD is usually under-repoted as a cause of death. The question is whether or not this is consistent.

What advantage does temporal epidemiology give?

If changes in prevalence could be linked to historical events, for instance the industrial revolution, that would be a major step to finding an aetiology for Parkinson's. As it is, no one heard the dog bark in the night. That, itself, is interesting.

Papers

A paper written nearly 50 years ago by Duvoisin and Schweitzer [1] gives some interesting insights into the rapid growth during the 19th and 20th centuries in the number of cases of PD, or paralysis agitans as it was known then.

Working from mortality data, the raw figures show a remarkable growth from an annual average for England and Wales of 21 cases in the latter half of the 1850s to 1600 by the start of the 1960s. This was a time of rising population, with people living longer. However, the authors put the main reason for the increase down to better reporting of the disease rather than higher real prevalence. But, as the authors point out, they cannot exclude that there was real growth.

A paper by Clarke [2] extends the period covered to 1989. The picture that he paints is the same: differences over time can be largely attributed to reporting changes and an ageing population. One difference that he points out, though, is that the introduction of levodopa extended the life expectancy of PwP by about 5 years.

A UK government report for the period 1979 to 2004 [3] reports:
"Mortality rates for mentions of Parkinson’s disease declined over the
period examined."
Again, this is thought to be due to PwP living longer.

References:

[1]"Paralysis Agitans Mortality in England and Wales, 1855-1962"
Duvoisin R., Schmeitzer M.
Brit. J. prev. soc. Med. (1966), 20, 27-33
http://pubmedcentralcanada.ca/pmcc/a...00081-0030.pdf

[2] "Mortality from Parkinson's disease in England and Wales 1921-89."
C E Clarke
J Neurol Neurosurg Psychiatry. 1993 June; 56(6): 690–693.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC489621/

[3] "Trends in mortality from Alzheimer’s disease, Parkinson’s disease and dementia, England and Wales, 1979–2004"
Griffiths C, Rooney C.
Office of National Statistics.
https://www.ons.gov.uk/ons/rel/hsq/h...-1979-2004.pdf

John