<P> The cause of Parkinson's disease is generally unknown, but believed to involve both genetic and environmental factors . Those with a family member affected are more likely to get the disease themselves . There is also an increased risk in people exposed to certain pesticides and among those who have had prior head injuries, while there is a reduced risk in tobacco smokers and those who drink coffee or tea . The motor symptoms of the disease result from the death of cells in the substantia nigra, a region of the midbrain . This results in not enough dopamine in these areas . The reason for this cell death is poorly understood, but involves the build - up of proteins into Lewy bodies in the neurons . Diagnosis of typical cases is mainly based on symptoms, with tests such as neuroimaging being used to rule out other diseases . </P> <P> There is no cure for Parkinson's disease, with treatment directed at improving symptoms . Initial treatment is typically with the antiparkinson medication levodopa (L - DOPA), with dopamine agonists being used once levodopa becomes less effective . As the disease progresses and neurons continue to be lost, these medications become less effective while at the same time they produce a complication marked by involuntary writhing movements . Diet and some forms of rehabilitation have shown some effectiveness at improving symptoms . Surgery to place microelectrodes for deep brain stimulation has been used to reduce motor symptoms in severe cases where drugs are ineffective . Evidence for treatments for the non-movement - related symptoms of PD, such as sleep disturbances and emotional problems, is less strong . </P> <P> In 2015, PD affected 6.2 million people and resulted in about 117,400 deaths globally . Parkinson's disease typically occurs in people over the age of 60, of which about one percent are affected . Males are more often affected than females at a ratio of around 3: 2 . When it is seen in people before the age of 50, it is called young - onset PD . The average life expectancy following diagnosis is between 7 and 14 years . The disease is named after the English doctor James Parkinson, who published the first detailed description in An Essay on the Shaking Palsy, in 1817 . Public awareness campaigns include World Parkinson's Day (on the birthday of James Parkinson, 11 April) and the use of a red tulip as the symbol of the disease . People with parkinsonism who have increased the public's awareness of the condition include actor Michael J. Fox, Olympic cyclist Davis Phinney, and late professional boxer Muhammad Ali . </P> <P> The movement difficulties found in PD are called parkinsonism and a number of different disorders feature parkinsonism . "Parkinsonism" is defined as bradykinesia (slowness in initiating voluntary movements, with progressive reduction in speed and range of repetitive actions such as voluntary finger - tapping) in combination with one of three other physical signs: muscular (lead - pipe or cogwheel) rigidity, tremor at rest, and postural instability . </P>

The clinical symptoms of parkinson’s disease can be divided into how many groups