Parkinson’s patients have lower blood levels of caffeine and its byproducts after consuming the stimulant, suggesting that caffeine could be used as a biomarker for diagnosing the disease.
The findings appeared in the study “Serum caffeine and metabolites are reliable biomarkers of early Parkinson disease,” published in the journal Neurology.
Caffeine is an organic molecule that, when consumed through coffee or tea, can stimulate the central nervous system.
There is evidence that daily caffeine consumption reduces the risk of developing Parkinson’s both in men and in women who are not taking hormone replacement therapy.
In addition, caffeine and two of its metabolites — byproducts produced in the body — reduce nerve cell death in the brain’s substantia nigra region, mice studies have shown. The substania nigra is the main brain area that Parkinson’s affects.
The researchers studied 108 Parkinson’s patients — 58 men and 50 women — and 31 healthy controls. The team also checked 67 other Parkinson’s patients — 33 men and 34 women — and 51 controls for mutations of caffeine-associated genes.
Participants drank between zero and five cups of coffee a day, except for one, who drank more than six.
Parkinson’s patients had lower blood serum levels of caffeine and nine of its metabolites — including the main byproducts theophylline, theobromine, and paraxanthine — than controls, researchers said. This was true regardless of the stage of patients’ disease and how much caffeine they were consuming.
Another finding was caffeine levels in patients with movement complications were lower than in those without.
Even though the findings showed a relation between caffeine serum levels and Parkinson’s, there was no significant association between the severity of the disease and the concentration of caffeine-related substances. There was also no significant difference in serum levels between men and women with Parkinson’s.
Importantly, researchers found no differences in caffeine-related gene mutations between patients and controls. They looked at genes involved in caffeine metabolism or that encoded the caffeine adenosine 2A receptor.
The results prompted the team to conclude that “caffeine metabolite profiles may be reliable diagnostic biomarkers for early Parkinson’s disease.”
Researchers acknowledged that the study had limitations. They noted that it “was conducted at a single university hospital” and that few participants had severe cases of Parkinson’s. The team excluded patients with a history of pneumonia or cancer.
In addition, any medications that participants were taking to deal with their Parkinson’s disease could have influenced their caffeine metabolism, the researchers said.
Nonetheless, the findings suggested that “lower levels of caffeine and caffeine metabolite profiles are promising diagnostic biomarkers” for early Parkinson’s disease, the team wrote.