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Science News

Caffeine May Improve Motor Symptoms of Parkinsonís Disease

Several studies have shown that people who drink caffeinated coffee or tea are less likely to develop Parkinson’s disease (PD). Yet scientists do not know if caffeine protects against the disease, or whether it could improve the symptoms of people who already have it. Now, in a study published in the August 14, 2012 issue of Neurology, researchers report that caffeine may improve some motor symptoms in people with Parkinson’s disease.

Researchers led by Ronald B. Postuma, M.D., M.Sc., at McGill University in Montreal, Canada, began the study to find out if caffeine could help people with Parkinson’s disease who suffer from excessive daytime sleepiness, a common non-motor symptom of the disease. Unexpectedly, the researchers found that although caffeine did not significantly help participants stay awake during the day, the stimulant did improve some motor symptoms of Parkinson’s disease.

For the study, Dr. Postuma and colleagues studied 61 people with Parkinson’s disease who also experienced daytime sleepiness, randomly dividing them into two groups: caffeine or placebo. Study participants, who were all taking levodopa to manage their Parkinson’s disease, were given a capsule containing either 100 mg caffeine (the equivalent of about one to two cups of coffee, depending on the type of coffee and strength of brew) or sugar twice daily for three weeks, then 200 mg twice daily for another three weeks. The study was double-blind, meaning that neither the participants nor the researchers knew to which group the participants had been assigned.

The researchers analyzed daytime sleepiness with a standard questionnaire. Although not the focus of the study, other characteristics such as motor symptoms, depression, and quality of life were also compared between the groups.

Results

  • Compared with the placebo group, the caffeine-treated group showed little or no improvement in daytime wakefulness.
  • At three and six weeks, people in the caffeine group showed greater improvement than the placebo group (by three and a half to four and a half points) in a standard test used to evaluate Parkinson’s disease symptoms, the Unified Parkinson’s Disease Rating Scale (UPDRS). In particular, the caffeine group had improved motor symptoms, including quicker motions and less rigidity.
  • The two groups showed no differences in quality of life, depression or sleep quality.

What Does It Mean?

This paper suggests that caffeine at the studied doses does not significantly reduce daytime sleepiness in people with Parkinson’s disease. In contrast, caffeine did appear to modestly improve some motor symptoms of Parkinson’s disease. However, because the initial focus of the study was daytime sleepiness, rather than motor symptoms, these results remain exploratory. A more detailed analysis should be conducted to confirm these effects. Also, researchers should examine the effects of caffeine in people with Parkinson’s disease who do not experience daytime sleepiness.

A possible limitation of the study is that some participants correctly guessed which group they were assigned to based on whether or not they felt more alert or energetic after taking the pill. This “unblinding” could have influenced the study’s results by altering people’s perceptions or expectations of their Parkinson’s disease symptoms. However, since the unblinding did not affect daytime sleepiness (for which there was no effect), it is unlikely that it explains the difference between the two groups. Another limitation is the relatively short duration (six weeks) of the study. Long-term caffeine use can cause people to develop tolerance to the stimulant, which may reverse any motor benefits.

Although this study provides evidence for a beneficial effect of caffeine on motor symptoms of Parkinson’s disease, the researchers still do not know why this effect occurs. One hypothesis is that caffeine’s benefits in Parkinson’s disease may stem from its ability to increase the production of dopamine, a neurotransmitter whose levels are reduced in Parkinson’s disease. Another idea is that caffeine somehow slows the neurodegenerative process that leads to Parkinson’s disease development and progression.

Doctors do not yet have enough information to justify prescribing caffeine as a treatment for Parkinson’s disease. However, doctors and people with Parkinson’s disease could take the results of this study into consideration when discussing overall dietary caffeine use.

Source Date: Aug 01 2012