Parkinson's disease commonly occurs in older individuals, although it may also occur in young adults. It is present worldwide and in all populations.
Men have a slightly higher prevalence rate than women.
No race or specific region of the world has been found to be completely devoid of the disease. The mean age of onset of Parkinson's disease is approximately 60 years. It usually occurs in patients over 50 years of age, and onset before age 25 is uncommon. The incidence and prevalence of the disease generally increase with increasing age. The Parsi community of Bombay, India was recently found to have the highest prevalence rates reported to date.