By Serena Gordon
Parkinson's disease is a neurodegenerative disorder that mainly causes problems with motor symptoms, such as tremors or difficulty walking. Previous studies have suggested that caffeine may have a protective effect against the disease, the researchers noted.
Currently, there's no good way to diagnose early Parkinson's disease. Many of the physical symptoms can mimic those of other conditions, so it often takes six months or longer to get a diagnosis, explained James Beck, chief scientific officer at the Parkinson's Foundation.
The new study from Japan included 108 people with Parkinson's disease without obvious memory problems and 31 age-matched healthy people without the disease to serve as the control group.
After an overnight fast, everyone's blood was tested for caffeine and 11 caffeine metabolites (which metabolize caffeine).
Both groups averaged similar amounts of daily caffeine consumption -- about two cups of coffee per day. But those with Parkinson's had lower levels of caffeine and lower amounts of nine out of the 11 metabolites. People with Parkinson's had about one-third the levels of caffeine in their blood compared to the control group.
The levels of caffeine and its metabolites didn't change with the severity of the disease. For example, people with more advanced disease didn't have even lower levels of caffeine or its metabolites.
The researchers also recruited an additional 67 people with Parkinson's and 51 healthy people to test for alterations in genes that are known to be related to caffeine metabolism. They found no differences in these genes between the groups.
Study co-author Dr. Shinji Saiki, an associate professor at Juntendo University School of Medicine in Tokyo, said the researchers believe that caffeine isn't absorbed properly in the small intestine of people with Parkinson's disease.
The researchers plan to study whether they can accurately detect Parkinson's disease before symptoms, or in the very earliest stage of symptoms, using caffeine and its metabolites.
Mark Frasier, senior vice president of research programs at the Michael J. Fox Foundation for Parkinson's Research, said, "I think this study is very intriguing. We need ways to measure and diagnose Parkinson's disease."
He noted that the researchers controlled the data to account for possible confounding elements, such as caffeine consumption. And they still found a significant difference in levels of caffeine and its metabolites for people with Parkinson's.
But Frasier added, "This is a relatively small study from one site. It needs to be replicated with a different, larger population."
The Michael J. Fox Foundation has collected blood samples from people with Parkinson's disease and healthy controls for researchers to use for "rapid replication" of the findings, Frasier added.
Beck agreed that the findings need to be replicated. Right now, he said, the study raises more questions than it answers, such as, "Why do people on medication for Parkinson's disease have lower levels of caffeine absorption? Is it an issue with the medications?"
Beck said it's also important to make sure these findings are specific to Parkinson's disease and not to other neurodegenerative diseases, such as ALS, also known as Lou Gehrig's disease.
Both Beck and Frasier said that even if this -- or some other test -- could diagnose early Parkinson's right now, there's no medication that can slow the progression of Parkinson's.
The only intervention that seems to help is exercise, both experts said. "Exercise seems to lead to lower problems with symptoms and helps people better deal with their disease," Beck said.
The study was published Jan. 3 in the journal Neurology.