Parkinson's disease (also called PD or Parkinson disease) is one of the most severely chronic progressive diseases of the nervous system. It refers to a group of conditions which are called motor system or movement disorders. It can also be called as brain disorder as it affects brain centers and creates difficulties in control, regulation, balance and coordination of the body movement. It may slow down or even result to loss (in extreme cases) of the physical movement of the patient The disease is named after Dr James Parkinson (1755-1824) who was basically an English apothecary surgeon, and also a geologist, and political activist. In his well-renowned essay named 'An Essay on the Shaking Palsy', he first described a condition called "paralysis agitans", which is now known as Parkinson's disease.

Parkinson's Disease is not only considered a disease of the aged people for it may also happen in many other forms. One form is idiopathic parkinsonism whose cause is still unknown. Drug induced parkinsonism may also happen in relation to medications being taken by the person. This type of Parkinsonism can be reversed by discontinuing the drug or lessening its dosage. Diseases such as encephalitis, stroke and head injury can also result to developing PD signs and symptoms.

Parkinson's disease happens with the damage of neurons or brain cells of a particular region of the brain (substantia nigra) which are required in producing the neurotransmitter called dopamine (that helps in the coordination of the body movement by sending signals). This results to a disorder in the patient's central nervous system which affects his/her motor abilities, speech, and various other functions. Thus, this disease creates difficulty in walking, talking, or any other activity that requires good muscular coordination.

Parkinson's disease grows quickly in some people than in others. Patient's daily activities start to be interfered by motor system disorders as the disease develops. Even various problems such as depression, disruption in sleep etc. may also results from this disease.

NIH (National Institutes of Health) usually conducts various research projects on parkinsonism. Researchers warns that by 2030, the number of people over age 50 affected by Parkinson's disease will double to 9 million. Over 1.5 million people are already affected with that disease in the United States and nearly 60,000 new people are being affected by it each year, adding to the estimated 1.5 million Americans who already have it.

PD can affect people with any age such as from younger to older, but it is mostly seen in the people with age between 50 and 60. Only 15 percent of Parkinson's disease patients are diagnosed before they are 50 years old. Its prevalence is same in both male and female person. If a person's family shows history of bearing Parkinson's disease, then there might be a possibility of developing that disease, although it is rarely identified to be caused by genetic reasons alone. PD rarely leads to death, but often makes the victim so much weak that he/she becomes vulnerable to various other diseases.