Caffeine level in blood may help diagnose people with Parkinson's disease

Testing the level of caffeine in the blood may be a simple way to diagnose Parkinson's disease, according to new research.

The study found that people with the debilitating condition had "significantly lower" levels of caffeine in their blood than people without the disease - even if they consumed the same amount of caffeine.

Study author Doctor Shinji Saiki, of Juntendo University School of Medicine in Japan, said: "Previous studies have shown a link between caffeine and a lower risk of developing Parkinson's disease, but we haven't known much about how caffeine metabolises within the people with the disease."

People in the study with more severe stages of the disease did not have lower levels of caffeine in the blood, suggesting that the decrease occurs from the earliest stages of the disease, according to Doctor David Munoz, of the University of Toronto in Canada, who wrote an editorial accompanying the study.

He said: "If these results can be confirmed, they would point to an easy test for early diagnosis of Parkinson's, possibly even before symptoms are appearing.

"This is important because Parkinson's disease is difficult to diagnose, especially at the early stages."

The study involved 108 people who had Parkinson's for an average of about six years and 31 people of the same age who didn't have the disease.

Their blood was tested for caffeine and for 11 byproducts the body makes as it metabolises caffeine. They were also tested for mutations in genes that can affect caffeine metabolism.

Caffeine count

The two groups consumed about the same amount of caffeine, with an average equivalent to about two cups of coffee per day.