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FeedThe Parkinson’s Paradox
New studies show that it’s more than a movement disorder.
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This much we know: Parkinson’s disease is a neurodegenerative movement disorder caused by the loss of the chemical messenger dopamine, which disrupts the brain’s organizing center and its ability to coordinate and control body movements. The link between dopamine-producing nerve cells and the area of the brain affecting motor skills makes the more common symptoms—tremors, slowed movement, balance problems, rigidity—relatively easy to identify. Less cut-and-dry are the changes in mood, sleep and thinking that have only recently been studied, suggesting new PD risk factors.
In its early stages, dopamine loss leaves more subtle clues. A person may be introverted or reserved. They might be perceived as ambitious and industrious, or serious, plodding and single-minded. A study published in May 2009 issue of the medical journal Brain suggests that even PD patients with little or no physical impairment can lack the mental capacity to process rewarding aspects of life.
Dopamine has already been linked to energy levels and risk-taking. PD patients gradually lose a significant amount of dopamine-producing cells, and experts have surmised that cautious, reserved behavior could be the result. It also makes sense that many PD sufferers show signs of depression—including lack of energy and motivation—long before they experience loss of motor control.
Before my father died last year of complications from Parkinson’s, he’d become more reserved and depressed, attributing the latter to “getting old.” He was a physician—one of two occupations linked to PD. But he was also a coffee drinker and a smoker, which are said to decrease your chances of developing the disease.
Still, researchers point out that there’s probably no “neuroprotective” benefit to tobacco smoke, nicotine or caffeine. “If you consider that person with PD is somewhat reserved and risk-adverse, it makes sense that you’re not going to see them with habits—drinking and smoking—generally associated with risk-takers,” says Daniel Kremens, a neurologist at Thomas Jefferson University Hospital who specializes in movement disorders.
At Jefferson, researchers are working to explain Parkinson’s-related damage to dopamine-producing cells. They’re also focusing on new risk factors. “There really are two hot areas of research right now,” Kremens says. “One has to do with the notion that we can no longer consider PD as strictly a motor-movement disorder. We also know now that there are non-motor symptoms like constipation and loss of a sense of smell that show up long before the tremors or rigidity.”
In a long-term research project known as the “Honolulu Heart Study,” depression and daytime sleepiness were recently linked to an increased risk of developing PD. These and other symptoms may have been identified as early as 1817 by James Parkinson, the British physician who gave his name to the disease.
Despite the high-profile struggles of actor Michael J. Fox, who was diagnosed with Parkinson’s disease at age 30, PD is one of the few disorders linked to getting older. In fact, the interplay between the disease process and normal aging has only complicated matters. The older you get, the more likely you are to develop PD. But if you define “old” as over 65, keep in mind that the mean age of Parkinson’s onset is 55.
