<Tr> <Th> Frequency </Th> <Td> 6.2 million (2015) </Td> </Tr> <Tr> <Th> Deaths </Th> <Td> 117,400 (2015) </Td> </Tr> <P> Parkinson's disease (PD) is a long - term degenerative disorder of the central nervous system that mainly affects the motor system . The symptoms generally come on slowly over time . Early in the disease, the most obvious are shaking, rigidity, slowness of movement, and difficulty with walking . Thinking and behavioral problems may also occur . Dementia becomes common in the advanced stages of the disease . Depression and anxiety are also common, occurring in more than a third of people with PD . Other symptoms include sensory, sleep, and emotional problems . The main motor symptoms are collectively called "parkinsonism", or a "parkinsonian syndrome". </P> <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>

Are there any related illnesses or ailments to parkinson's disease
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