Epidemiology

In the UK:

• ▶. prevalence about 1/800, annual incidence 1/8000

• ▶. 1% of people over the age of 65 years are affected

• ▶. a general practitioner will have three to four patients at any one time

• ▶. median age of onset is 60 years, with a slight male preponderance

• ▶. disease onset to death is about 15 years, twice the number of observed to expected deaths (standardised mortality ratio 2:1).

The disorder is no respecter of race or creed Literary and historical precedents to Parkinson's seminal description suggest it is unlikely to be a post-industrial disease. In common with other neurodegenerative diseases, increasing age is the major risk factor although 15% of cases present before the age of 45 years and the incidence may decrease somewhat in the ninth decade of life. Genetic factors are now considered to significantly increase risk.

Habitual non-cigarette smokers are twice as likely to develop the illness as smokers and there may also be a mildly increased risk to men who do not take any caffeine, perhaps related to dopamine's role in reward pathways, rather than due to a protective effect of nicotine or coffee. Loose associations with rural living, middle age, obesity and lack of exercise, well water ingestion and pesticide exposure have also been reported. Environmental toxins such as …