Epidemiologic studies consistently link caffeine, a nonselective adenosine antagonist, to lower risk of Parkinson disease (PD). This six-week randomized, placebo-controlled trial was conducted to assess the effects of caffeine (100 mg twice daily for three weeks and then 200 mg twice daily for three weeks) upon daytime somnolence, motor severity, and other nonmotor features in 61 PD patients with daytime somnolence. Caffeine resulted in a non-significant reduction in Epworth Sleepiness Scale score (-1.71 points; 95% CI -3.57 to 0.13). However, somnolence improved on the Clinical Global Impression of Change (+0.64; 95% CI 0.16-1.13), with significant reduction in Epworth Sleepiness Scale score on per-protocol analysis (-1.97; 95% CI -3.87 to -0.05). Caffeine reduced the total Unified Parkinson’s Disease Rating Scale score (-4.69 points; 95% CI -7.7 to -1.6) and the objective motor component (-3.15 points; 95% CI -5.50 to -0.83). Modest improvement in global health measures were found but no changes in quality of life, depression, or sleep quality were noted. The authors concluded that caffeine provided only equivocal borderline improvement in excessive somnolence in PD, but improved objective motor measures. These potential motor benefits suggest that a larger long-term trial of caffeine is warranted. Neurology. 2012 Aug 1. PMID: 22855866
