Coffee didn't work to treat Parkinson's, but may play role in prevention
Researchers had hoped caffeine could be used to relieve symptoms of Parkinson's
Caffeine didn't work as a medication to relieve movement symptoms in people with Parkinson's, Canadian researchers have found.
Earlier findings had raised hopes that caffeine could treat symptoms of Parkinson's disease. A small 2012 study hinted that caffeine could ease uncontrolled movements and stiffness symptoms in people with Parkinson's disease. This study had focused primarily on the sleep disorders associated with Parkinson's.
This would have been a very mildly effective, obviously, but incredibly inexpensive, astonishingly safe, medication if it would've worked for Parkinson's disease- Dr. Ronald Postuma, McGill University
Parkinson's disease is a neurological condition related to the death of specific brain cells, including cells that control movement, mood, sleep and cognition. It can manifest with tremors, slowness of movement, stiffness or rigidity and sleep disorders, interfering with co-ordination, balance, strength, as well as the ability to speak clearly.
Now Dr. Ronald Postuma, a neurologist at McGill University, and his colleagues have the results from their longer study involving 121 people who had been diagnosed with Parkinson's disease. The subjects' average age was 62 and they'd been diagnosed with the disease an average of four years prior.
Half of the subjects were assigned to receive caffeine and half a placebo.
- Coffee's good, coffee's bad — why can't scientists make up their mind?
- Caffeine in coffee a genetic quirk unrelated to chocolate or tea
That longer study, published in this week's issue of the journal Neurology, found no improvement in motor signs or symptoms from taking caffeine pills that were the equivalent of about two cups of drip coffee a day.
"It's obviously disappointing. You don't want to be running trials for things that don't work," Postuma said in an interview with CBC News.
"This would have been a very mildly effective, obviously, but incredibly inexpensive, astonishingly safe, medication if it would've worked for Parkinson's disease. So it had to be done. It just didn't work in the way that we wanted."
Postuma said it's clear from many other studies that people who don't drink coffee have an increased risk of developing Parkinson's disease. The question is why.
Before the findings of this latest caffeine trial were in, one explanation was that the popular beverage was a medication, of sorts, for Parkinson's disease. That's now likely off the table.
While caffeine doesn't work as a treatment, perhaps it helps to prevent Parkinson's disease. We may never know, because a randomized trial that is large and long enough to test it in a controlled way is unlikely to happen, Postuma said. Especially when people can simply try in on their own at home.
Postuma said anyone who likes coffee or who wants to take a caffeine pill to stay awake, should feel free to do so. That's as true for someone with Parkinson's as everyone else.
Postuma said caffeine is an example of a potential treatment that looked good in early phase studies and didn't pan out.
In this case, the short-term benefits initially seen seemed to dissipate as the body adjusted to caffeine. Think of how drinking coffee in the evening may keep someone awake when they're not used to it, and yet have no effect among connoisseurs.
"This is yet another illustration of how you really do have to confirm things," he said.
The researchers say that's an important message given how patients often clamour to try foods, beverages and herbal products with even the suggestion of potential benefit.
While caffeine has been studied a lot, high-quality research is rare. Looking more broadly, the findings could help shed some light on other aspects of Parkinson's disease susceptibility.
It does seem like the nose-to-the-grindstone people have a higher risk of Parkinson's disease- Dr. Ronald Postuma, neurologist
People naturally show a range of differences in their brain rewards systems, including personality traits that determine where they fall on the spectrum between loyal, hard workers who like to keep it safe and folks who love the thrill of skydiving.
On average, people with Parkinson's disease tend to fall into the risk-averse end of the spectrum, Postuma said. The disease shows up in a disproportionate number of nonsmokers and non-coffee drinkers. Like the clearly unhealthy habit of smoking, drinking coffee is considered a self-rewarding behaviour that comes with a hit of dopamine.
"It does seem like the nose-to-the-grindstone people have a higher risk of Parkinson's disease," Postuma said. "Maybe it starts really early and actually changes your personality. Maybe if you get the Parkinson's changes and your dopamine system was never that powerful to begin with, you're going to present a few years earlier. It's one of the mysteries."
Postuma cautions his latest study tested caffeine as a medication to treat symptoms only and didn't address prevention.
The American Academy of Neurology, which published the findings, said one limitation of the study was that caffeine was not measured in the blood of participants. It's possible that a higher dose may have different effects. Nor were other properties of coffee measured or tested.
The study was supported by the Canadian Institute of Health Research, the Webster Foundation and Quebec's health research fund (Fonds de Recherche du Québec – Santé).
With files from CBC's Amina Zafar