Caffeine has previously been linked to a lower risk of developing Parkinson's disease, but now new research says the ubiquitous stimulant may also help treat disease symptoms.
In a small study of 61 people with Parkinson's disease, Canadian researchers found that giving the caffeine equivalent of about three cups of coffee per day improved motor symptoms, such as slow movement and stiffness. Interestingly, caffeine didn't significantly improve daytime sleepiness, a common symptom in Parkinson's disease.
"Caffeine treats Parkinson's disease," said the study's lead author, Dr Ronald Postuma, an associate professor in the department of neurology at McGill University in Montreal.
"There was a modest effect on sleepiness that didn't reach statistical significance, but I think it was clear that it helps patients," he said. "Where we saw the most potential benefit from caffeine was on motor aspects and symptoms. People felt better and were more energetic. You could see on the exam that they were better."
Parkinson's disease is a degenerative disorder that causes shaking, stiffness, slow movements and difficulty with balance. More than one million Americans have Parkinson's disease, and more than 50 000 people are diagnosed with the disease each year, according to the National Parkinson Foundation.
How the study was done
In the current study, published in the journal Neurology, half of the group of Parkinson's patients was randomly assigned to receive caffeine treatment, while the other half received an inactive placebo.
To be included in the study, the volunteers had to consume less than 200 milligrams (mg) of caffeine daily - about two cups of coffee - and they couldn't have any heart rhythm problems, uncontrolled high blood pressure, or an active ulcer.
For the first three weeks of the study, those receiving caffeine were given 100 mg of caffeine twice daily - once when they got up and again at lunchtime.
During the second three weeks, the dose was increased to 200 mg twice daily.
Using a test called the Epworth Sleepiness Scale score, the researchers found that while there was a reduction in this score for those treated with caffeine, indicating less daytime sleepiness, that decrease didn't reach statistical significance. Still, Postuma said he believed that caffeine did help improve the level of daytime sleepiness, and that with a bigger study group, a benefit would likely become clearer.
Motor symptoms were judged using the Unified Parkinson's Disease Rating Scale score. There was a modest overall improvement of 5 points in this score.
What the study found
In addition, there were improvements in the speed of movement and the amount of stiffness in the treatment group versus the placebo group.
"[This study] is important even though it failed to reveal a benefit for caffeine in improving sleepiness in Parkinson's disease. Interestingly, it did reveal a clinically significant potential motor benefit," said Dr Michael Okun, national medical director of the National Parkinson Foundation. "It will be interesting to see if these findings hold up, and caffeine becomes a treatment approach in Parkinson disease," he added.
Postuma said the mechanism behind coffee's effect on Parkinson's symptoms isn't yet known, but it's believed to block receptors of a substance called A2A adenosine that may play a role in some Parkinson's symptoms. Two new drugs that block A2A adenosine receptors and work in a very similar manner to caffeine are currently in development, he said.
"Their results are almost the same as what we're getting. They may be making and selling expensive caffeine," Postuma said.
"One interesting aspect about the actions of caffeine in Parkinson's disease is that they are thought to be mediated through blocking the A2A adenosine brain receptor. There are several drugs in Parkinson's trials that have similar mechanisms of action, and it would be interesting to perform head-to-head trials comparing caffeine to these drugs," Okun said.
Postuma would like to conduct larger trials on caffeine to see if the effects of the stimulant wear off over time.
The good news, he said, is that caffeine is "incredibly safe and well-tolerated".
Coffee not so bad
So, "if you've been avoiding caffeine because you think it's bad, you can stop. If you're sleepy during the day, you can try it," Postuma said. People with heart rhythm problems, uncontrolled high blood pressure or active ulcers should talk with their doctors about whether they should have caffeine in their diet, however.
Home-brewed coffee tends to have less caffeine than what you get at a coffee shop, Postuma noted. Most people shouldn't go over 400 mg to 500 mg a day (about four to five cups), he advised. And, if you don't want caffeine to interrupt your sleep, try to have your last cup of coffee with lunch.
Caffeine - good or bad?
Learn more about Parkinson's disease from the U.S. National Institute of Neurological Disorders and Stroke.
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