According to a 2016 study (Global Burden of Disease Study), Parkinson's is estimated to affect 6.1 million people worldwide. Since many people go undiagnosed, it’s likely that the true prevalence is much higher, and with people living for longer, the number of people living with the disease is almost certain to rise in the future.
Parkinson’s can occur at any age. Early onset Parkinson's (also known as young onset Parkinson’s), is defined as occurring in someone under the age of 40. Research suggests that genetics may play more of a role in early or young onset than in people who are over the age of 40 at the time of diagnosis.
The symptoms of early or young onset Parkinson's, as well as how well the condition responds to medication, may differ slightly from older onset Parkinson’s, although for some people these can be very similar.
The majority of patients diagnosed with Parkinson’s disease (around 80–85%) have what is called idiopathic Parkinson’s disease (meaning that the disease has no known cause). This type tends to respond well to drugs that work by increasing or substituting dopamine molecules in the brain.