Parkinson's disease

Parkinson's disease (PD), or simply Parkinson's, is a chronic degenerative disorder of the central nervous system that affects both the motor system and non-motor systems. The symptoms usually emerge slowly, and as the disease worsens, non-motor symptoms become more common. Early symptoms are tremor, rigidity, slowness of movement, and difficulty with walking. Problems may also arise with cognition, behaviour, sleep, and sensory systems. Parkinson's disease dementia becomes common in advanced stages of the disease. The motor symptoms of the disease result from the death of nerve cells in the substantia nigra, a region of the midbrain that supplies dopamine to the basal ganglia. The cause of this cell death is poorly understood, but involves the aggregation of the protein alpha-synuclein into Lewy bodies within the neurons. Collectively, the main motor symptoms are known as parkinsonism or a parkinsonian syndrome. The cause of PD is unknown, but a combination of genetic and environmental factors are believed to play a role. Those with an affected family member are at an increased risk of getting the disease, with certain genes known to be inheritable risk factors. Environmental risks include exposure to pesticides, and prior head injuries; a history of exposure to trichloroethylene is also suspected. Conversely, caffeine and nicotine appear to be protective. Diagnosis is mainly based on symptoms, with motor symptoms being the most frequently presented. Tests such as neuroimaging (magnetic resonance imaging or imaging to look at dopamine neuronal dysfunction known as DaT scan) are used to help rule out other diseases. Parkinson's disease typically occurs in people over the age of 60, of whom about one percent are affected. Males are affected at a ratio of around 3:2 compared with females. When it is seen in people before the age of 50, it is called early-onset PD. By 2015, PD affected 6.2 million people and resulted in about 117,400 deaths globally. The number of people with PD older than fifty is expected to double by 2030. The average life expectancy following diagnosis is 7–15 years.