Parkinson's Disease

Epidemiology

Symptoms of Parkinson’s disease (PD) generally appear in people between 40 and 70 years of age, with the incidence of PD peaking in people in their sixties. Onset of PD before the age of 20 is generally termed ‘juvenile PD’ (JPD) and onset between the ages of 21 and 40 years is termed ‘early’ or ‘young’ onset PD (EOPD, YOPD) (Gomez et al, 1997; Schrag et al, 1998).

JPD is rare; one study reported 4 people out of 380 with PD were under 20 years of age (Adams et al, 1997). It is difficult to establish a definite diagnosis of JPD; diagnosis often involves identifying a specific pattern of nigral degeneration or identifying PD associated with Huntington's or Wilson's disease (Fahn, 1995). EOPD is also uncommon, with an incidence of approximately 5% of all PD cases (ie about 0.001% per year). PD is more common in men than in women, with a male–female ratio of 3:2.

The overall incidence of PD in the UK is estimated at 0.02% per year (Clarke, 2001) and in North America about 1% of the population over the age of 65 years have PD (Adams et al, 1997). The point prevalence of PD in North America is about 160 people per 100,000 people and the incidence is about 20 people per 100,000 people per year (Fahn, 1995). Both prevalence and incidence increase until the age of 70 in North America, they reach approximately 55 and 120 cases, respectively (Fahn, 1995).

The incidence in all countries where vital statistics are kept is the same and, considering this frequency, incidence in a family on the basis of chance occurrence could be as high as 5%.