What is Parkinson’s Disease?

Parkinson’s disease is characterized by a decrease in a brain chemical named dopamine and the death of neurons in a part of the brain known as the substantia nigra. The loss of these neurons leads to the characteristic Parkinson’s tremor, other debilitating movement symptoms and problems with cognition, mood, and sleep. The disease primarily affects people after age 65, though younger people can develop an early-onset form.

Parkinson’s disease is the second most common neurodegenerative disease after Alzheimer’s.

What causes it?

The cause is unknown; however, there are a number of known risk factors. Men are 50 percent more likely than women to develop Parkinson’s disease; exposure to pesticides and other toxins increases risk. Head trauma and depression are also thought to increase a person’s chances of developing Parkinson’s disease. A number of recently discovered genetic risk variants are reported to increase a person’s risk as well – these may prove scientifically useful in identifying the underlying mechanisms of Parkinson’s disease.

How is it treated today?

Although there are some therapies that help with the symptoms of Parkinson’s disease, none can address the underlying cause of the disease. Levodopa is a drug that replaces dopamine, the main chemical produced by the neurons that Parkinson’s disease attacks. However, its effect tends to wear off after four to seven years and can cause unwanted side effects. Other drug treatments try to mimic the action of dopamine, protect it from breakdown or preserve motor function through other molecular pathways. And for some people with Parkinson’s disease, surgically implanted electrodes can relieve symptoms.

Can we develop more effective treatments?

Because we currently have little understanding of how Parkinson’s disease starts and progresses, the challenge of developing a disease-modifying drug is formidable. Researchers and clinicians lack a reliable diagnostic or biomarkers that can be used to determine whether a candidate drug affects disease progression at a cellular level.

These scientific opportunities – as well as emerging tools such as brain imaging, data mining, and stem cells – suggest that an aggressive and well-organized basic research effort can give us the answers we need to understand, diagnose, and treat Parkinson’s disease.

Yet there are reasons for optimism. Genetic studies have also identified a number of proteins that are associated with the disease, and researchers have found potential targets for therapeutic drugs. Wearable movement sensors may enable clinical trials to collect massive amounts of data on disease progression. Perhaps most promising, a number of cellular mechanisms have been linked to Parkinson’s disease. These include the improper folding of a protein called alpha-synuclein, causing the formation of aggregates known as Lewy bodies; malfunctions in energy-producing cellular organelles known as mitochondria; activation of an inflammatory response and defects in the recycling process of degrading cellular components. Major progress would come from understanding how these processes contribute to disease, which of these processes are most central, and how they go wrong.

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