Researchers at Juntendo University have reported the potential use of blood levels of caffeine and its byproducts as biomarkers for Parkinson’s disease. The finding is promising for the development of a method enabling early identification of the disease.1

Parkinson’s disease is a degenerative disorder of the central nervous system, affecting the body’s motor system. Symptoms include shaking, rigidity, and difficulty with walking. There is evidence that daily caffeine consumption reduces the risk of developing Parkinson’s.

A team of researchers led by Nobutaka Hattori, MD, PhD, a neurologist at the Juntendo University School of Medicine, have studied whether traces of caffeine in the blood, after drinking coffee, can be indicative of Parkinson’s disease. The researchers found that caffeine levels are significantly lower in patients with the disease; caffeine concentrations could therefore be used as an indicator of Parkinson’s, particularly in its early stages.

The researchers studied a group of 139 people, both men and women, with and without Parkinson’s disease. Each person drank between zero and five cups of coffee per day, except for one participant who drank more than six. The researchers then checked the participants’ blood serum for traces of caffeine and its 11 so-called downstream metabolites—small molecules produced during caffeine-induced metabolic processes in the human body.

The scientists found that serum levels of caffeine and almost all of its metabolites—including caffeine’s main byproducts, paraxanthine, theobromine, and theophylline—were lower in patients with Parkinson’s disease. Although the data obtained by Hattori’s team showed that there is a clear relation between a person’s caffeine serum levels and having Parkinson’s disease, there was no significant association between the concentrations of any of the caffeine-related substances and the severity of a subject’s disease. Also, there was no significant difference in serum levels between male and female patients, even though males are known to suffer from Parkinson’s disease more often than females.

According to Hattori and colleagues, caffeine and caffeine metabolite levels in the blood may be “early diagnostic biomarkers for the disease.” Moreover, the study results “further indicated the neuroprotective effects of caffeine,” according to the authors.


  1. Fujimaki M, Saiki S, Li Y, et al. Serum caffeine and metabolites are reliable biomarkers of early Parkinson disease. Neurology. Published online in advance, January 3, 2018; doi: 10.1212/WNL.0000000000004888.