Parkinson's: Caffeine may lower risk but doesn't slow progression

• Evidence from past epidemiological studies suggests that caffeine may protect against developing Parkinson’s disease in the future.
• A recent study investigates whether caffeine may help treat the condition.
• The researchers conclude that caffeine does not improve symptoms in people who already have Parkinson’s disease.
• However, the study found that consuming caffeine just before a brain scan may influence the results, which may eventually lead to changes in patient advice.

Multiple strands of evidence suggest that people who consume higher levels of caffeine are less likely to develop Parkinson’s than people who do not drink coffee.

Whether caffeine can help treat Parkinson’s is an open question. A recent study, which appears in the journal Annals of Neurology , concludes that caffeine does not improve symptoms.

However, the scientists also identify that caffeine consumption in the hours before a brain scan may influence the reliability of the scan. This important finding may eventually help guide clinical practice.

A brief primer on Parkinson’s

Parkinson’s is a progressive neurodegenerative disease characterized by motor symptoms, such as tremor.

Medical News Today spoke with Daniel Truong, MD , a neurologist and medical director of the Truong Neuroscience Institute at MemorialCare Orange Coast Medical Center in Fountain Valley, CA.

Truong, who was not involved in the study, is also editor-in-chief of the Journal of Clinical Parkinsonism and Related Disorders . He explained how Parkinson’s develops.

“Alpha-synuclein is a protein that aggregates abnormally in Parkinson’s, forming so-called Lewy bodies. These aggregates can trigger an inflammatory response. The accumulation of alpha-synuclein,” he told us, “leads to the release of pro-inflammatory cytokines, which exacerbate neuronal damage.”

In particular, this buildup damages “dopaminergic neurons in the substantia nigra.” Neurons in this brain region help fine-tune motor control, so, as they become damaged, it produces the motor symptoms of Parkinson’s.

Links between caffeine and Parkinson’s

A number of large-scale studies in the early 2000s unearthed links between Parkinson’s and caffeine. Researchers showed that individuals who consumed the most caffeine had the lowest risk of developing Parkinson’s disease.

Multiple studies backed these findings up. Scientists found that individuals who drank more coffee — but not decaffeinated coffee — had a significantly lower risk of Parkinson’s.

Why caffeine protects against the development of Parkinson’s is an open question, but it may have something to do with adenosine, Truong told MNT :

“Caffeine is an adenosine receptor antagonist, meaning it blocks the action of adenosine, a neurotransmitter that can inhibit the release of dopamine. By blocking adenosine receptors, caffeine may indirectly increase dopamine release, which could potentially protect against Parkinson’s disease.”

However, there are a number of theories. He also told us that caffeine is anti-inflammatory and interacts with other neurotransmitters and cellular processes.

This association spurred researchers on to investigate whether caffeine might help slow Parkinson’s disease in people who have already developed the condition. These studies, however, were inconclusive.

Some research found that certain symptoms improved when treated with caffeine, but others got slightly worse. Meanwhile, other studies suggested that caffeine might help slow the development of symptoms.

With many outstanding questions about caffeine and Parkinson’s, the latest study takes a fresh look at this question.

The scientists behind this new study asked whether caffeine might improve dopamine function in people with Parkinson’s, thereby improving motor function in the long run.

What role does caffeine play in Parkinson’s?

In the latest study, the scientists recruited 163 people with early Parkinson’s disease and 40 healthy controls. Each participant underwent a single photon emission computed tomography ( SPECT ) scan, a type of scan used to assess Parkinson’s progression.

SPECT assesses striatal dopamine transporter binding , a measure of dopaminergic nerve activity: a lower level of binding means the system is not working as it should and, therefore, the disease has progressed further.

The scientists also noted each participant’s caffeine intake and took other clinical measures. After an average of 6.1 years, 44 of these participants were re-examined.

The authors found that people with high coffee consumption had 8.3–15.4% lower dopamine transporter binding in their striatal regions compared with low coffee consumers. In other words, those with a high caffeine intake had reduced dopaminergic activity compared with those drinking less coffee.

Also, caffeine consumption was associated with a progressive decline in dopamine binding over time. Despite this, symptoms in the high-caffeine group were not measurably worse.

MNT spoke with the lead author, Valtteri Kaasinen, MD, PhD , a professor of neurology and chief physician for the Department of Clinical Neurosciences at the University of Turku, Finland. He told us how these findings were contrary to his expectations.

“Given that caffeine seems to reduce the risk of Parkinson’s disease, we expected to find increased brain dopamine transporter binding in patients who consumed higher amounts of caffeine,” said Kassinen.

“We also anticipated that this difference would become more pronounced over the course of the disease and correlate with less severe motor symptoms,” he continued.

“Instead, we observed that dopamine transporter binding in the brain was actually decreased in high caffeine consumers, and this decrease increased over time without affecting motor symptoms. This was a surprising and unexpected finding.”

– Valtteri Kaasinen, MD, PhD

How caffeine affects brain scans for Parkinson’s

The scientists also found that consuming caffeine in the hours before a SPECT scan briefly increased dopamine transporter binding. If confirmed, this might be clinically important. Currently, guidelines do not suggest patients avoid caffeine before a scan.

“Our findings imply that there may be a transient increase in dopamine transporter binding due to acute caffeine consumption, which could complicate the interpretation of imaging results, especially in borderline cases,” Kaasinen explained.

MNT asked whether clinical guidelines should be changed. The study author’s reply was: “Our results suggest that caffeine intake before a dopamine transporter binding scan can influence the scan’s results.”

“Therefore,” he continued, “it would be advisable for patients to avoid consuming coffee or caffeine for 24 hours before imaging.” However, he also told us that further research is needed to confirm the results.

Truong agreed that we need more evidence first, and that “the decision to recommend caffeine avoidance before a scan should be based on multiple factors, including the specific imaging technique being used, the patient’s overall health status, and potential interactions between caffeine and any medications they may be taking.”

Caffeine doesn’t reduce Parkinson’s symptom severity

Earlier research shows that caffeine consumption may protect against developing Parkinson’s later in life.

However, this recent study demonstrates that caffeine does not reduce the severity of symptoms or slow disease progression in people who already have the condition.

The results also suggest avoiding caffeine before a SPECT scan may provide a more accurate picture of disease progression. However, scientists need to carry out more research to confirm this relationship.

While much ink has been spilled over the links between Parkinson’s and caffeine, this is certainly not the end of the mystery.