There have been several recent studies suggesting that caffeine may reduce the risk of developing Parkinson’s disease, however in this week’s edition of the journal Neurology, there is a new study suggesting that caffeine may be a reasonable treatment for the Parkinson’s disease motor symptoms. In this month’s What’s Hot column, I will review the scientific literature on caffeine and Parkinson’s disease, and also discuss the implications of the latest study.
The idea that caffeine may be important in Parkinson’s disease began with a series of epidemiological type of “risk factor” studies that in sum revealed a potentially reduced risk for Parkinson’s when caffeine intake was increased over a lifetime. Several large studies have carefully examined populations of patients, and all have uniformly concluded that higher caffeine intake seems to be closely associated with a reduced chance of developing Parkinson’s disease. These findings have important implications for the field.
Animal experiments have, like in human trials and epidemiological studies, revealed a potential caffeine benefit for Parkinson’s disease sufferers. The benefit is believed to be underpinned by caffeine’s action in blocking the adenosine A2A brain receptor. Several A2A blocking drugs have either been studied, or are currently being studied. In humans there have been several small studies and also anecdotal observations that support the idea that there is a mild to moderate caffeine benefit in Parkinson’s.
The latest study appeared in this week’s edition of the journal Neurology. Postuma and colleagues randomized 61 patients with Parkinson’s disease to caffeine or alternatively to a placebo. The investigators aimed to improve sleepiness, but caffeine failed to keep subjects more awake. However, on the UPDRS Parkinson’s disease motor scale, patients who received caffeine had an approximate 5 point improvement. The caffeine study was only performed for six weeks, the sample was extremely small, and it was hard to blind who got caffeine and who did not. The results should therefore be interpreted with caution, and will need to be replicated in a much larger study, presumably using a primary motor outcome.
These results suggest an intriguing symptomatic benefit. Since the results have been mirrored by several smaller studies, and also by the studies of adenosine A2 antagonists, patients should begin to pay attention to the link between caffeine and Parkinson’s disease.
What do these study results specifically mean for patients? The mild motor benefit of taking 100mg-200mg of caffeine twice daily seemed to be real. Patients wishing to benefit will need to be sure they track the amount of caffeine intake each day, and also remember that many things (e.g. tea, coffee, soft drinks) other than coffee may have caffeine content. Also, they should remember that the study did not examine higher dosages of caffeine, and it is possible that the effects on tremor and other symptoms could worsen at higher dosages. Finally, patients should be aware that in most studies participants develop tolerance to the effects of caffeine, and this could negate the benefits. The true importance of this most recent caffeine study will be in helping to spur the development of new drugs and new targets for the treatment of Parkinson’s disease.