Context: Somnolence is a recognized adverse effect of dopamine agonists. Two new dopamine agonists, pramipexole and ropinirole, have been reported to cause sudden-onset sleep spells in patients with Parkinson disease (PD) while they were driving. The frequency of these spells and whether driving should be restricted has yet to be established.
Objective: To determine the frequency of and predictors for sudden-onset sleep and, particularly, episodes of falling asleep while driving among patients with PD.
Design, setting, and participants: Prospective survey conducted between January and April 2000 in 18 clinics directed by members of the Canadian Movement Disorders Group; 638 consecutive highly functional PD patients without dementia were enrolled, of whom 420 were currently drivers.
Main outcome measures: Excessive daytime sleepiness and sudden-onset sleep as assessed by the Epworth Sleepiness Scale and the Inappropriate Sleep Composite Score. The latter score, designed for this study, addressed falling asleep in unusual circumstances. The 2 scales were combined in 3 separate formats: dozing off, sudden unexpected sleep, and sudden blank spells.
Results: Excessive daytime sleepiness was present overall in 327 (51%) of the 638 patients and in 213 (51%) of the 420 drivers. Patients taking a variety of different dopamine agonists had no differences in Epworth sleepiness scores, in the composite score, or in the risk of falling asleep while driving. Sixteen patients (3.8%) had experienced at least 1 episode of sudden onset of sleep while driving (after the diagnosis of PD); in 3 (0.7%), it occurred without warning. The 2 risk factors associated with falling asleep at the wheel were the Epworth Sleepiness Scale score (odds ratio [OR], 1.14; 95% confidence interval [CI], 1.06-1.24) and the Inappropriate Sleep Composite Score (OR, 2.54; 95% CI, 1.76-3.66). A standard Epworth Sleepiness Scale score of 7 or higher predicted 75% of episodes of sleep behind the wheel at a specificity of 50% (exclusion of the question related to driving provided 70% sensitivity and 52% specificity), whereas a score of 1 on the Inappropriate Sleep Composite Score generated a sensitivity of 52% and specificity of 82%.
Conclusions: Excessive daytime sleepiness is common even in patients with PD who are independent and do not have dementia. Sudden-onset sleep without warning is infrequent. The Epworth score has adequate sensitivity for predicting prior episodes of falling asleep while driving and its specificity can be increased by use of the Inappropriate Sleep Composite Score. It is unknown if routinely performing these assessments could be more effective in predicting future risk for these rare sleep attacks. Patients should be warned not to drive if they doze in unusual circumstances.