Sleepiness in Parkinson's disease: a controlled study

Sudden-onset sleep episodes while driving have been reported in Parkinson's disease (PD) patients, and termed sleep attacks because they were reported to be irresistible and to occur without warning. We postulate that these episodes are due to excessive daytime sleepiness secondary to the high frequency of sleep disorders in PD patients and the sedative effects of dopaminergic medications. We assessed the frequency and relationship between excess daytime sleepiness and sleep episodes while driving (SE) in patients with PD. We evaluated 101 consecutive PD patients presenting to the Movement Disorder Center at the Mount Sinai School of Medicine using a questionnaire that incorporated a subjective estimate of sleepiness, the Epworth Sleepiness Scale (ESS) and information on disease severity and dopaminergic medications. One hundred age-matched respondents without PD served as a control population. Excess daytime sleepiness was reported in 76% of PD patients compared to 47% of controls (P < 0.05). The mean ESS scores for PD patients was 9.1 +/- 6.1 versus 5.7 +/- 4.4 in controls (P < 0.001). ESS scores > or =10 were observed in 40.6% of PD patients compared to 19% of controls (P < 0.01) and 24% of PD patients had scores > or =15, compared to 5% of controls (P < 0.001). Sleep episodes while driving were experienced by 20.8% of PD drivers compared to 6% of control drivers (P < 0.05). The mean daily levodopa (L-dopa) dose equivalent was 1,142 +/- 858 mg in PD drivers who experienced a SE while driving compared to 626 +/- 667 mg in those who had not (P < 0.05). Similarly, ESS was significantly greater in drivers with a SE than in those without (11.6 +/- 6.4 vs. 8.4 +/- 4.1; P < 0.05). Logistic regression analysis demonstrated that ESS and mean daily L-dopa dose equivalents were predictors of sleep episodes while driving, whereas age, gender, disease severity, and individual dopaminergic agents were not. These findings support the notion that sleep episodes while driving in PD patients are related to excess daytime sleepiness and dopaminergic load. Physicians should advise and treat patients accordingly.