Parkinson’s disease is a chronic and progressive degenerative disorder of the central nervous system that impairs motor skills, speech and other functions. It is usually characterized by muscle rigidity, tremor, postural instability, and a slowing or loss of physical movement.

Ageing is an important risk factor, and the incidence of Parkinson’s increases with age, although about 4% are diagnosed before the age of 50. An estimated 7-10 million people worldwide (roughly 1 in 1,000 of the total population) are thought to be living with Parkinson’s.

A high proportion of sufferers also experience mild cognitive impairment as the disease advances, including executive dysfunction (impaired problem solving, fluctuations in attention, etc), slowed cognitive speed and memory problems, particularly with working memory, episodic memory and with recalling learned information. In many cases (about 25-30% of cases), this eventually develops into full-blown dementia, although memory problems in Parkinson’s are typically milder than in Alzheimer’s disease. Non-motor symptoms such as memory loss remain the most under-addressed area for research into Parkinson’s disease.

Parkinson’s disease is the result of decreased stimulation of the motor cortex by the basal ganglia, usually due to the insufficient formation and action of the neurotransmitter dopamine in the neurons in an area of the brain called the substantia nigra. When cells that normally produce dopamine die off, the symptoms of Parkinson’s often appear. Its main cause is thought to be genetic, although the exact mechanism is still unclear.

There is no cure for Parkinson’s, but some limited effect in counteracting the effects can be provided by treatment involving drugs which help boost the brain’s production of dopamine such as levodopa, or dopamine agonists that mimic the action of dopamine, as well as some other more experimental and controversial treatments. However, most of the drugs have some unpleasant side-effects, and some non-motor symptoms may actually be aggravated by the treatments used for the motor symptoms.