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.
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
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