Epidemiologic studies consistently find an inverse association between caffeine use and PD. Numerous explanations exist, but are difficult to evaluate as caffeine's symptomatic effect and tolerability in PD are unknown.
We designed an open-label, 6-week dose-escalation study of caffeine to establish dose tolerability and evaluate potential motor/nonmotor benefits. Caffeine was started at 200 mg daily and was increased to a maximum of 1,000 mg.
Of 25 subjects, 20 tolerated 200 mg, 17 tolerated 400 mg, 7 tolerated 800 mg, and 3 tolerated 1,000 mg. The most common adverse events were gastrointestinal discomfort, anxiety, and worsening/emerging tremor. At 400 mg daily, we found potential improvements in motor manifestations and somnolence (UPDRS III: -4.5 ± 4.6, P = 0.003; Epworth: -2.0 ± 3.0, P = 0.015).
Maximum dose tolerability for caffeine in PD appears to be 100 to 200 mg BID. We found pilot preliminary evidence that caffeine may improve some motor and nonmotor aspects of PD, which must be confirmed in longer term, placebo-controlled, clinical trials.