Caffeine levels in the blood may help to diagnose Parkinson’s disease (PD), according to researchers from the Juntendo University School of Medicine (Tokyo, Japan).
The study, published in Neurology, indicated that individuals with PD exhibited lower bloodstream levels of caffeine in comparison with non-PD sufferers, despite consuming the same amount of the substance.
The researchers examined 108 people who had been suffering with PD for approximately 6 years. A control group of 31 similarly-aged individuals who did not have the disease was also enrolled. Participants had their blood tested for caffeine as well as 11 by-products of caffeine metabolism. The study also tested for mutations in genes known to influence caffeine metabolism.
Although the groups consumed similar amounts of caffeine, approximately two cups of coffee daily, PD sufferers were found to have significantly lower levels of caffeine and nine of the 11 by-products than the control group. The team observed that caffeine level was, on average, 79 picomoles per 10 microliters in the healthy controls, compared with 24 picomoles per 10 microliters in sufferers. Furthermore, for one of the by-products, levels were below the detectable amount in over 50% of PD sufferers.
Genetic testing, however, found no differences in caffeine-related genes between groups.
Interestingly, those in the study with more established PD did not display decreased caffeine levels, suggesting that the reduction occurs in early stages of the disease. This may help to provide earlier diagnosis of the disease, potentially detecting its presence before symptoms appear.
However, the fact that people with severe PD were not included in the trial may limit its significance, by affecting the ability to identify links between caffeine levels and disease severity. It is also worth noting that all individuals with PD in the study were taking medication, hence it is possible that these drugs may be affecting the metabolism of caffeine.