Parkinson's disease (PD) is a common neurodegenerative disorder characterized by motor disability and many disabling non-motor symptoms. Excessive daytime somnolence (EDS) is found in up to 50% of patients with PD, and can cause considerable impairment of quality of life. At present, the only proven treatment for EDS in PD is modafinil, an alerting agent with an unknown mechanism of action. However, modafinil is only moderately effective and is very expensive. Caffeine is a very well tolerated and inexpensive alerting agent that is used worldwide, but very few patients with PD use it as therapy for EDS. It is unclear whether this is because it does not help EDS in PD, has side effects, or simply has not been considered because of lifelong patterns of non-use.
If caffeine can be demonstrated as an effective agent for EDS in PD, it will likely become the first-line agent for EDS. This will result in considerable cost savings for patients and health care payers, as well as potentially helping those who cannot tolerate, do not respond to, or cannot afford modafinil.
Another compelling question of interest to patients with PD is whether caffeine may be neuroprotective. Despite intensive research, no treatment has been found that can slow the progression of neurodegeneration in PD. Recently numerous epidemiologic studies have linked lifelong use of caffeine to a lower risk of PD. Although the mechanism for this finding is unclear, supporting evidence from animal models suggests that a true neuroprotective benefit of caffeine is a strong possibility. Alternatively, caffeine could have a benefit on motor manifestations of PD, which would prevent diagnosis of PD. Any finding of a symptomatic benefit of caffeine on motor manifestations of PD will have obvious and important implications for treatment of persons affected with PD and for planning of neuroprotective trials. Any finding of a neuroprotective benefit of caffeine will almost certainly result in its immediate widespread use in PD, with profound implications for patient care.
The present proposal is for a double blind randomized placebo controlled crossover trial that will answer three important questions in PD: is caffeine useful for the treatment of EDS in patients with PD? does caffeine have any symptomatic effect on the motor manifestations of PD? and, does caffeine have an acceptable tolerability and side effect profile that will allow planning of an eventual neuroprotective trial? Patients with PD who have EDS with an Epworth sleepiness scale of \>10 will be randomized to caffeine therapy (100 mg twice per day for three weeks, then 200 mg twice per day for three weeks) or placebo. A final assessment will be performed after a 4-week washout. A total of 52 patients will be randomized over a two-year period. The primary outcome measure will be the change in Epworth sleepiness scale between patients receiving caffeine versus placebo. Secondary outcome measures will include other sleep scales, tolerability measures, and measures of motor function and overall quality of life. After tests to assess normal distribution, analysis will be with two-sample t-test.
