Caffeine affects dopamine function in the brain in patients with Parkinson's disease

The results of the study, published in the Annals of Neurology journal, show that caffeine consumption before diagnostic imaging of brain dopamine may also affect the imaging results.

Previous research has shown that regular caffeine consumption is associated with a reduced risk of developing Parkinson's disease. However, there is little research examining the effect of caffeine on the progression of the disease in patients who have already been diagnosed.

A study conducted by the University of Turku and Turku University Hospital (Tyks) in Finland examined how caffeine consumption affects dopamine function in the brain over a long period in patients diagnosed with Parkinson's disease. Dopamine function in the brain was assessed using single photon emission computed tomography (SPECT) to measure dopamine transporter (DAT) binding.

"The association between high caffeine intake and a reduced risk of Parkinson's disease has been found in epidemiological studies. However, our study is the first to focus on the effect of caffeine on disease progression and symptoms in relation to dopamine function in Parkinson's disease," says Valtteri Kaasinen, professor of neurology at the University of Turku and the principal investigator of the study.

Caffeine consumption does not affect symptoms of Parkinson's disease

The clinical study compared 163 patients with early-stage Parkinson's disease with 40 healthy control participants. Examinations and imaging were performed twice for a subsample, with an average of six years between the first and second imaging sessions.

Changes in dopamine transporter binding in the brain were compared with patients' caffeine intake, which was assessed both using a validated questionnaire and by determining concentrations of caffeine and its metabolites in blood samples.

The results showed that patients with high caffeine intake experienced an 8.3% to 15.4% greater reduction in dopamine transporter binding compared to patients with low caffeine intake.

However, the observed decrease in dopamine function is unlikely to be due to a large decrease in the number of dopamine neurons due to caffeine consumption. This is most likely a compensatory mechanism in the brain, which has also been observed in healthy people after consumption of caffeine and other stimulants.

"Although caffeine may offer some benefits in reducing the risk of Parkinson's disease, our study shows that high caffeine consumption does not benefit dopamine systems in already diagnosed patients. High caffeine consumption did not reduce symptoms of the disease, such as improved motor function " says Kaasinen.

Another important finding of the study was the observation that a recent dose of caffeine, for example in the morning before an imaging session, transiently increased DAT binding values in humans. This may complicate the interpretation of clinically commonly used DAT brain imaging results.

The study results suggest that patients should abstain from coffee and caffeine for 24 hours before undergoing DAT imaging.