The way your body metabolises your cup of coffee each morning may determine your chances of developing Parkinson's disease, according to a study.

The findings showed that people with Parkinson's disease had significantly lower levels of caffeine in their blood than people without the disease, even if they consumed the same amount of caffeine.Thus, testing the level of caffeine in the blood may provide a simple way to aid the diagnosis of Parkinson's disease, the researchers 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," said Shinji Saiki, MD at the Juntendo University School of Medicine in Tokyo.

"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," added David G. Munoz, MD, at the University of Toronto."This is important because Parkinson's disease is difficult to diagnose, especially at the early stages," Munoz noted.For the study, published in the journal Neurology, the team involved 108 people who had Parkinson's disease for an average of about six years and 31 people of the same age who did not have the disease and consumed about two cups of coffee per day. 

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.The caffeine level was an average of 79 picomoles per 10 microliters for people without Parkinson's disease, compared to 24 picomoles per 10 microliters for people with the disease.However, there were no differences found in the caffeine-related genes between the two groups.