31 October 2014 - PARKINSON'S DISEASE

PARKINSON'S DISEASE

G'day folks,

Today I feature one of the many scourges of the modern world.

WHAT IS IT?

Parkinson’s disease (PD) is a progressive, neurodegenerative disease that belongs to the group of conditions called motor system disorders. PD cannot yet be cured and sufferers get worse over time as the normal bodily functions, including breathing, balance, movement, and heart function worsen.

Parkinson’s disease most often occurs after the age of 50 and is one of the most common nervous system disorders of the elderly. The disease is caused by the slow deterioration of the nerve cells in the brain, which create dopamine. Dopamine is a natural substance found in the brain that helps control muscle movement throughout the body.

Other neurodegenerative disorders include Alzheimer’s disease, Huntington’s disease, and amyotrophic lateral sclerosis, or Lou Gehrig’s disease.

 WHO GETS PARKINSON’S DISEASE?

Parkinson’s disease affects both men and women but occurs about 50% more in men than women. The average age for the onset of PD is 60 years old, however 5 – 10% of cases, called “early onset,” begin as early as 40 years old. The National Institute of Neurological Disorders and Stroke estimates that close to 500,000 people in the United States have PD, although most other estimates run as high as 1,00,000 people.  Approximately 50,000 Americans are diagnosed each year.  The reason the numbers are approximate is that there is no set of guidelines to measure Parkinson’s disease and therefore, in this country, no national registry of cases.

People with PD have about the same life expectancy as the normal population, however complications during the late stages of the disease can lead to choking, pneumonia, and falls that can be fatal. The disease progresses at different rates in different people. A more severe progression is often seen in people who develop PD at an earlier age.

 CAUSES?

Despite intense research efforts around the world, the molecular causes of Parkinson’s disease are still unclear. What doctors and scientists do know is that PD is caused by the progressive loss of dopamine brain cells (neurons) in a part of the brain called the substantia nigra, which produces the chemical dopamine. As the cells die, less dopamine is produced and transported to the striatum, the area of the brain that co-ordinates movement.

Under the influence of dopamine, signals from the striatum regulate all forms of movement.  Parkinson’s disease symptoms begin when the loss of dopamine reaches a critical point, typically when 50 to 80 percent of dopamine neurons have died. Because there is such a dramatic loss of dopamine neurons by the time the disease is diagnosed, it extremely difficult for doctors and scientists to research PD at its earliest stages. Thus, much of the research done on PD uses animal models that most closely mirror the onset of PD in humans.

The question of why dopamine neurons degenerate is being intensely investigated by scientists in our labs, and all over the world. In recent years, great strides have been made in solving this mystery. While there is still no definitive answer, it is now widely accepted that there is no single “cause” that triggers the disease. Instead, Parkinson’s disease likely results from a confluence of inherited (genetic / familial) and environmental factors that interact in complex ways to set disease processes in motion. Around 5 percent of cases are hereditary in the classic sense that if one or both parents have it, their children are at higher risk. But in the vast majority of cases, no obvious familial link is present. Instead, it is believed that there are a variety of triggers, including exposure to toxins and severe head injuries.  Also, individuals may inherit a degree of susceptibility to the disease, which only causes Parkinson’s disease when other factors are present.

 TREATMENT?

Treatments are available only for the symptoms of Parkinson’s disease. None of the currently available treatments can halt or even slow the loss of neurons in Parkinson’s disease.
One of the most effective and widely used treatments for the symptoms of PD is carbidopa-levodopa. Levodopa, also called L-dopa, is a drug that is converted into dopamine in the brain. Levodopa is often combined with carbidopa, which improves the action of levodopa and reduces some of its side effects, particularly nausea.

The side effects of L-dopa, with or without carbidopa, are considerable and can include Dyskinesia (muscle spasms), low blood pressure, arrhythmia (abnormal heart rhythms), gastrointestinal problems, nausea, hair loss, sleep disorders, confusion, anxiety and hallucinations.

Within 4 – 6 years of treatment with L-dopa, the effects of the drug in many patients begin to last for shorter periods of time after a dose (called the “wearing off effect”). The duration of the “on” state becomes shorter and “wearing off” happens sooner. The “wearing off” state can result in a tremor or slowness in movement, painful muscle spasms that can cause contortions in the neck, jaw, midsection, eyes and feet. In some patients, the “wearing off” states are predicable, allowing the patient to plan accordingly.  For others it is unpredictable. Unfortunately, doctors have yet to understand why these fluctuations are predictable in some patients and not in others. In response to the “wearing off effect,” patients may choose to increase the dosage of levodopa, or frequency they take it, but in doing so they face an increased risk of dyskinesia.

ECONOMIC IMPACT OF DISEASE

According to the American Journal of Managed Care, the annual economic impact of Parkinson’s disease in the United States is around $10.8 billion, including both direct medical expenses and indirect costs such as lost income, disability payments and medical costs.

The financial burden of Parkinson’s disease on individuals and their families is immense. Drugs commonly used to treat Parkinson’s disease can cost up to $6,000 per year per patient.  Surgical treatments for Parkinson’s disease can cost $25,000 or more. As the disease progresses, institutional care at an assisted-living facility or nursing home may be required and these costs can exceed $100,000, per person annually.

The mental and emotional cost of PD on patients, families and friends cannot be quantified. What is clear is that investment in medical research that leads to better treatments for Parkinson’s disease can save millions of dollars each year. Studies have indicated that for every dollar spent on high quality research $13 could be saved in direct and indirect costs. If new therapies could be found that could produce even a modest ten percent delay in the progression of Parkinson’s disease, hundreds of millions of dollars could be saved every year.

Despite these prospects, Parkinson’s disease continues to receive far less federal research support than most other disorders. Privately funded research must fill these huge gaps in federal funding.

Clancy's comment: I hope this has been interesting and informative.

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