What is Parkinson’s Disease?
Parkinson’s disease is a chronic, degenerative, neurological condition. The primary symptoms of the disease are: tremor, rigidity, slowed movement (bradykinesia) and impaired balance (postural instability). Other common motor symptoms include loss of facial expression, speech and swallowing problems, and gait problems. Many patients also encounter non-motor symptoms: constipation; cognitive impairment; depression, anxiety and/or apathy; fatigue; and sleep disruptions.
Many but not all of the symptoms of Parkinson’s disease result from the loss of dopamine-producing cells in various parts of the brain, including a region called the substantia nigra. Dopamine is a naturally-occurring chemical (neurotransmitter) that allows nerve cells in the brain to transmit messages between each other and then to muscles to allow normal movement to take place. Loss of dopamine causes neurons to fire without normal control, leaving patients less able to direct their movement.
The symptoms of Parkinson’s disease appear when 60-80 percent of dopamine in the brain is depleted, Both the type and severity of symptoms – motor and non-motor – vary from individual to individual. Also, the pace at which the disease progresses varies on an individual basis. Consequently, some experts have suggested that Parkinson’s is more than one disease.
Parkinson’s disease is one of the several central nervous system conditions classified as a “movement disorder”.
What Causes Parkinson’s Disease?
The exact cause of Parkinson’s disease is unknown, although research suggests a combination of genetic and environmental factors. Parkinson’s patients likely fall along a continuum with exclusively genetic causes at one end and exclusively environmental causes at the other.
Some cases of Parkinson’s disease are genetic in origin (e.g., the result of a genetic mutation). However, for most Parkinson’s patients, the cause of the disease probably lies somewhere in the middle of the continuum. The consensus among researchers is that, in the majority of cases, genetic and environmental factors interact to cause Parkinson’s. It is still generally impossible to determine what caused an individual’s Parkinson’s. With these patients, clinicians use the term “idiopathic” to denote the unknown nature of the cause of the disease.
That being said, a number of studies have highlighted factors that are associated with either greater or lesser risk of Parkinson’s disease. For example, head injury and pesticide exposure have been associated with higher rates of Parkinson’s, while smoking and caffeine consumption have been associated with lower risk. These studies, however, do not definitively link these factors with Parkinson’s.
Who Gets Parkinson’s Disease?
Parkinson’s disease affects one in 100 people over age 60. While the average age at onset is 60, people have been diagnosed as young as 18. Since there is no objective test or biomarker for Parkinson’s, estimates of the number of people living with the disease vary; but recent research indicates that at least one million people in the United States, one hundred thousand in Canada, and more than five million worldwide, have the disease. Approximately 60,000 Americans and 6,000 Canadians are diagnosed with Parkinson’s each year, but this number does not reflect the thousands of cases that go undetected.
Men are one and a half times more likely than women to have Parkinson’s disease.
Incidence of Parkinson’s disease increases with age, but an estimated four percent of patients are diagnosed before the age of 50. An estimated eighty-five percent of those diagnosed are over the age of 65. As people are living longer, the prevalence of Parkinson’s disease is expected to increase significantly in the next few decades.
What are the Treatments for Parkinson’s Disease?
While a cure remains elusive, there are many effective treatments for Parkinson’s disease. Drug therapies can ameliorate symptoms and enhance the quality of life of Parkinson’s patients. Surgical intervention such as deep brain stimulation has proven very effective for patients who qualify for this treatment. Non-drug treatments (e.g., exercise, speech therapy, counseling) may help relieve some of the motor symptoms of the disease. There is real promise in the area of stem cell research; considerable progress has been made in creating dopamine-producing cells from stem cells. However, many features of Parkinson’s, which are not very responsive to currently available medications, are not related to dopamine, so alternative approaches need to be pursued. Research efforts are focused on finding a cure; treatments that slow the progress of the disease; and treatments that improve both motor and non-motor symptoms.