Researchers in Japan have discovered that people with Parkinson's may have lower levels of caffeine in their blood after drinking tea and coffee.
The results, published in the online journal Neurology®, suggest that caffeine may be processed differently by those with the condition. The researchers hope this could lead to simple diagnostic blood test.
The study looked at the blood levels of caffeine - as well as the byproducts the body turns it into - in 108 people with Parkinson's and 31 people of the same age who did not have the condition.
The researchers found that, despite drinking about the same amount of caffeinated beverages, the levels of both caffeine and byproducts was lower in those with Parkinson's. They also suggest that the test might work early in the early stages of the condition.
Tricky to diagnose
There is currently no definitive diagnostic test for Parkinson's. Instead, specialists use clinical judgement and tests that rule out other conditions. This can take time, which causes stress and, in some cases, can lead to misdiagnosis.
This is the first time results on the use of caffeine as a biomarker have been reported. The researchers discovered they could use the levels of caffeine and its byproducts to correctly identify those with Parkinson's in this study 98% of the time.
Important questions still to answer
Professor David Dexter, Deputy Director of Research at Parkinson's UK, comments on these results:
"The lack of a definitive test to detect and measure Parkinson's means that diagnosis can be incredibly difficult, particularly in the condition's early stages.
"Not only does this cause stress for people awaiting a diagnosis, it is one of the key obstacles in the way of developing treatments that slow or stop the progression of this devastating condition.
"We have known of a link between caffeine and Parkinson’s for some time, but up to now this was only related to risk of developing the condition. Here, for the first time, researchers suggest an entirely new association with how caffeine is processed in the body.
"However, due to the lack of participants with other conditions in this study, there is no evidence that this test could distinguish Parkinson's from other neurological conditions. The authors also point out it is unclear if the levels of caffeine in the blood were due to a change in metabolism, or simply because the caffeine was not absorbed in the gut.
"As such, further research is needed before we know if this test holds any promise for making diagnosis more accurate, quicker and less stressful."
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