Sleep disturbances and excessive daytime sleepiness in Parkinson disease: an overview

Sleep disturbances are frequent in Parkinson disease. These disorders can be broadly categorized into those that involve nocturnal sleep and excessive daytime sleepiness. The disorders that are often observed during the night in PD include sleep fragmentation that may be due to recurrent PD symptoms, sleep apnea, Restless Leg Syndrome/ periodic limb movements and REM sleep behavior disorder. Excessive daytime sleepiness is also a common occurrence in PD. EDS can arise from several etiologies, and patients may have more than one etiology responsible. The causes of EDS include nocturnal sleep disorder with sleep deprivation and resulting daytime somnolence, the effect of drugs used to treat PD, and possibly neurodegeneration of central sleep/wake areas. Appropriate diagnosis of the sleep disturbance affecting a PD patient can lead to specific treatments that can consolidate nocturnal sleep and enhance daytime alertness.     

Sleep disruption, daytime somnolence and ''sleep attacks'' in Parkinson''s disease: a clinical survey in PD patients and age-matched healthy volunteers

Recent case reports of 'sleep attacks' (SA) in patients with Parkinson's disease (PD) generated concerns about drug-induced daytime somnolence in this population. However, there are nearly no comparative data on sleep and vigilance problems between PD patients and normal controls. We performed a cross-sectional survey in PD patients and age-matched controls using a structured questionnaire on PD history, treatments, co-morbidity, activities of daily living, habits, exercise, sleep pattern, driving, pre-existing nocturnal problems, daytime somnolence, episodes of SA and the circumstances in which such episodes occurred. Daytime somnolence was also measured with the Epworth Sleepiness Scale (ESS) and sleep quality with the Pittsburgh Sleep Quality Index (PSQI). 176 PD patients and 174 controls were included. The same proportion of PD patients (27%) and controls (32%) reported episodes of SA, but these were more frequent in PD patients and occurred more frequently during situations requiring attention (10.8% vs. 1.7%, p<10(-3)). More PD patients had abnormal daytime somnolence (ESS) and poor sleeping quality (PSQI). The most consistent factor associated with SA was the duration of levodopa therapy and the predictive value of an abnormal ESS score was rather poor (40.7%). Abnormal daytime somnolence and poor sleep quality at night are more frequent in PD patients than in normals. However, SA are reported in both groups, although less frequently in the normals during activities that requires attention.     

Daytime sleep in Parkinson's disease measured by episodes of immobility

Excessive daytime sleepiness (EDS) is common in Parkinson's Disease (PD). Actigraphy uses periods of immobility as surrogate markers of nighttime sleep but there are no examples of its use in assessing EDS of PD. A commercial wrist worn system for measuring bradykinesia and dyskinesia also detects 2 min periods of immobility, which have a 85.2% concordance with the detection of sleep by ambulatory daytime polysomnography, (p < 0.0001 Chi Squared). High Epworth Sleepiness Scores (ESS) were associated with a proportion of time immobile (PTI) (p = 0.01 Mann–Whitney U). The median PTI between 0900 and 1800 h w in 30 age matched control subjects was 2%, representing 10 min and PTI at or above the 75th percentile (5% or 27 min) was taken as a high level. PD patients had higher PTI (median 4.8%) than controls (p < 0.0001, Mann–Whitney U). PD subjects with a high PTI had more bradykinesia, less dyskinesia and higher PDQ39 scores than those with low PTI. There was no relationship between PTI and dose or type of PD medications. However, in 53% of subjects, PTI increased in the 30–60 min after levodopa confirming that in some subjects levodopa results in increased sleepiness. In summary, immobility is a surrogate marker of daytime sleep in PD, confirmed by correlation with PSG and ESS. PD subjects measured this way are more likely to be sleepy and sleepy PD subjects are more likely to be bradykinetic and have a higher PDQ39. Levodopa leads to an increase in sleepiness in more than half of subjects post dosing.     

Levodopa use and sleep in patients with dementia with Lewy bodies

Sleep disturbance and excessive daytime somnolence (EDS) are features of Parkinson's disease (PD) and dementia with Lewy bodies (DLB) that may be influenced by dopamine replacement therapy. The effect of levodopa on sleep and EDS in DLB is unknown and unclear in PD. The aim of this study is to determine if levodopa treatment alters sleep symptoms and EDS in DLB. Dopamine naïve patients with DLB (n = 15; mean mini mental state examination (MMSE) score 17.7(4.6)) and PD (n = 9; mean MMSE 25.5(2.2)) were assessed using the Epworth sleep scale, Parkinson's disease sleep scale, and the neuropsychiatric inventory prior to initiating treatment with levodopa. All measures were repeated after 3 and 6 months of levodopa therapy. The median final daily levodopa dose was 300 mg in both groups. Baseline sleep measures were comparable between groups. Levodopa treatment did not affect sleep or lead to increased EDS in DLB patients. The use of levodopa does not appear to adversely affect subjective sleep measures or increase EDS in DLB patients. © 2009 Movement Disorder Society     

Increased daytime sleepiness in Parkinson's disease: a questionnaire survey.

We evaluated the frequency and severity of excessive daytime sleepiness in an outpatient population with Parkinson's disease in comparison to age-matched controls and examined its relationship with antiparkinsonian drug therapy and sleep history. Increased daytime sleepiness and involuntary sleep episodes have been described in Parkinson's disease, but the etiology is not completely understood. The Epworth Sleepiness Scale (ESS), a validated questionnaire for daytime sleepiness, was prospectively administered to 99 consecutive outpatients with Parkinson's disease and 44 age-matched controls. In addition, a short sleep-screening questionnaire was used. The ESS revealed significantly increased daytime sleepiness in PD patients compared to controls (7.5 +/- 4.6 vs. 5.8 +/- 3.0, P = 0.013). The ESS score was abnormally high (10 or more) in 33 % of PD patients and 11.4% of controls (P = 0.001). ESS was not different between PD patients on levodopa monotherapy and those on levodopa and dopamine agonists, or between patients taking ergoline or non-ergoline dopamine agonists. In PD patients and in controls, sleepiness was significantly associated with reported heavy snoring. Increased daytime sleepiness is more frequent in patients with PD than in elderly controls. Similar to controls, increased daytime sleepiness in PD patients is correlated with heavy snoring.     

老年帕金森病患者日间过度思睡的临床调查及相关因素分析

目的了解老年帕金病(PD)患者日间过度思睡(EDS)的临床情况及相关因素。方法收集北京医院老年PD患者80例和年龄、性别相匹配的健康对照者50名,采用爱泼沃斯思睡量表(ESS)评定EDS,简易精神状态量表(MMSE)评定智能状况,比较PD患者和健康对照的EDS情况,同时对PD患者进行改良Webster评分、Hoehn-Yahr(H-Y)分期、Hamilton抑郁和焦虑量表调查,并询问是否具有夜间易醒、疲倦、不宁腿综合征、日间睡眠发作、夜间入睡困难、是否应用多巴受体激动剂及多巴胺药物的用量。根据ESS评分情况将PD患者分为EDS组(ESS≥10)和非EDS组(ESS<10分),并对两组间的上述调查项目进行比较。同时以ESS总分为因变量,以计量资料年龄、Hoehn-Yahr分级、左旋多巴用量、Webster评分、病程、Hamilton抑郁和焦虑评分及睡眠时间为自变量进行多元逐步回归分析,分析ESS评分与以上各因素的相关性。结果 80例PD患者中23例(28.8%)ESS≥10分,健康对照组5名(10.0%)ESS≥10分,两组有差异有统计学意义(χ2=6.40,P=0.01)。EDS组23例(男10例、女13例),年龄(72.26±5.94)岁,日间疲倦18例(78.26%),Hamilton抑郁量表评分(13.57±3.31)分,Hamilton焦虑量表评分(19.13±5.38)分,病程(7.65±4.12)年,非EDS组57例(男40例、女17例),年龄(68.58±5.27)岁,日间疲倦18例(31.58%),Hamilton抑郁量表评分(7.32±2.71)分,Hamilton焦虑量表评分(13.25±5.12)分,病程(5.55±3.40)年,两组间比较有统计学差异(均P<0.05);两组患者Hoe-hn-Yahr分级、改良Webster评分、应用左旋多巴剂量、是否应用多巴受体激动剂、夜间睡眠时间、入睡困难、不宁腿综合征、夜间易醒均无统计学差异(均P>0.05)。多元逐步回归分析结果显示,PD患者年龄和抑郁程度与ESS评分相关(分别回归系数=0.10,标准偏回归系数=0.16,P=0.04;回归系数=0.59,标准偏回归系数=0.66,P=0.00),抑郁程度相关性更强。结论老年PD患者EDS较为常见,可能受年龄和抑郁情绪的影响,但与疾病严重程度可能不存在相关性。     

Effect of exogenous melatonin on sleep and motor dysfunction in Parkinson's disease

Abstract Insomnia, sleep fragmentation and excessive daytime sleepiness are common in Parkinson's disease (PD) and may contribute to the reduction of cognition and alertness in those patients. Melatonin has been shown to improve sleep in several conditions. In experimental models of PD, melatonin can ameliorate motor symptoms. To evaluate the effect of melatonin on sleep and motor dysfuntion in PD, we studied 18 patients (Hoehn & Yahr I to III) from a PD clinic. Prior to treatment, motor dysfunction was assessed by UPDRS II, III and IV. Subjective sleep quality was assessed by the Pittsburgh Sleep Quality Index (PSQI) and daytime somnolence by the Epworth Sleepiness Scale (ESS). Full polysomnography (PSG) was performed in all subjects. Patients were then randomized to receive melatonin (3mg) or placebo one hour before bedtime for four weeks. All measures were repeated at the end of treatment. On initial assessment, 14 patients (70%) showed poor quality sleep (PSQI > 6) and eight (40%) excessive daytime sleepiness (ESS > 10). Increased sleep latency (50%), REM sleep without atonia (66%), and reduced sleep efficiency (72%) were found on PSG. Eight patients had an apnea/ hipopnea index greater than 15 but no severe oxygen desaturation was observed. Sleep fragmentation tended to be more severe in patients on lower doses of levodopa (p = 0.07). Although melatonin significantly improved subjective quality of sleep (p = 0.03) as evaluated by the PSQI index, PSG abnormalities were not changed. Motor dysfunction was not improved by the use of melatonin. Undetected differences in motor scores and PSG findings may have been due to a small sample size and a type II error.     

Snoring and excessive daytime sleepiness in Parkinson's disease

Recent recognition of daytime sleepiness in Parkinson's disease (PD) has prompted a search for its causes. Sleepy patients may be more susceptible to sleep attacks after the use of dopamine agonists and the recognition of sleep disturbances in PD may influence important therapeutic decisions. To identify clinical factors influencing excessive daytime sleepiness (EDS) and sleep complaints in PD, we studied 86 consecutive patients with clinical diagnosis of PD using a sleep questionnaire, the Epworth Sleepiness Scale, the Unified Parkinson's Disease Rating Scale and the Montgomery and Asberg Depression Rating Scale. Patients with cognitive dysfunction were not included in the study. We found that 49 patients (53.3%) had insomnia, 45 (49.9%) restless legs syndrome (RLS), 51 (55.4%) vivid dreams, 61 (71.8%) snoring and 29 (31.5%) had EDS. RLS was more frequent in patients with longer duration of illness. Snoring was the most important risk factor associated with EDS (OR=3.64, 95% CI=1.11-11.9, P=0.03) and a marginal association between motor dysfunction and EDS was observed (OR=1.06, 95% CI=1.00-1.12, P=0.05).     

Excessive daytime sleepiness and sleep episodes in Japanese patients with Parkinson's disease

In Parkinson's disease (PD), sudden unexpected sleep episodes and excessive daytime sleepiness (EDS) while driving and engaging in social activities are important problems. We conducted a multi-center study to clarify the prevalence and contributing factor of EDS and sleep episodes in Japanese patients with PD. We evaluated 188 patients with PD (85 men, 103 women) and 144 age-matched controls for sleepiness. EDS was defined as an Epworth sleepiness scale (ESS) score of >or=10. ESS score was significantly higher (6.6+/-4.2 vs. 5.6+/-3.8) and prevalence of sleep episodes was higher in PD than in controls (6.4% vs. 0.7%). PD patients with EDS were more likely to have sleep episodes (22.5% vs. 2.0%), higher score for disease severity and depressive symptoms, and on higher dose of dopaminergic agents than those without EDS. However, there were no differences in nocturnal disturbances between the two groups. ESS score was not different between patients taking ergot and non-ergot dopamine agonists. Logistic regression analysis demonstrated that mental state, total dose of dopaminergic agents, and ESS score were significant predictors of sleep episodes. ESS score of >or=10 had 75% sensitivity and 82.4% specificity for sleep episodes. These results suggest that sleepiness in PD is dependent on disease itself and dopaminergic treatment rather than nocturnal disturbances.     

Evaluation of somnolence in Parkinson's disease: comparison with age- and sex-matched controls

The authors found a significantly higher prevalence of daytime somnolence in 201 patients with PD compared with 214 age- and sex-matched healthy control subjects (Epworth Sleepiness Scale score 5.6 vs 4.6). The prevalence of "sleep attacks" (SA) was about seven times higher in patients with PD than in control subjects (13.9% vs 1.9%; p < 0.0005). Multivariate analysis demonstrated that a higher dose of levodopa and longer duration of disease significantly predicted for SA in patients with PD. Epworth Sleepiness Scale scores of > or =10 had 71.4% sensitivity and 88.4% specificity for SA.     

A study of excessive daytime sleepiness and its clinical significance in three groups of Parkinson's disease patients taking pramipexole, cabergoline and levodopa mono and combination therapy

Summary. Objective. To determine if therapy with an ergot and a non-ergot dopamine agonist and levodopa confers an increased risk of excessive daytime sleepiness and secondary "sleep attacks" in Parkinson's disease (PD). Methods. Comparative study of three clinical groups taking, pramipexole (Group 1, n = 19, 8 monotherapy), cabergoline (Group 2, n = 22, 10 monotherapy), and levodopa monotherapy (Group 3, n = 14). Clinical and demographic characteristics, occurrence of "sleep attacks", and assessment of daytime sleepiness [using the Epworth Sleepiness Scale (ESS)], recorded. Results. No patients reported "sleep attacks". Mean ESS scores: Group 1 (pramipexole) 8.0 ± 4.5 (range 0–16), Group 2 (cabergoline) 8.1 ± 3.9 (range 0–19), Group 3 (levodopa), 8.1 ± 5.5 (range 1–18). There was no significant difference between groups (p = 0.897). Scores of ≥16 indicating excessive daytime sleepiness (EDS) were evenly distributed throughout treatment groups, particularly in older patients with more advanced disease. Conclusions. Received March 31, 2000; accepted August 3, 2000     

Daytime somnolence in patients with Parkinson's disease

We studied daytime sleepiness in 160 patients with Parkinson's disease and 40 normal subjects. We compared the prevalence of daytime sleepiness in patients who were taking levodopa alone, levodopa with bromocriptine, levodopa with ropinirole, and levodopa with pramipexole. We found that (1) all these anti-Parkinson drugs can cause daytime sleepiness; (2) ‘dozing off’ correlated highly with ‘falling asleep without warning’; (3) after statistical adjustment for confounding variables there was no significant difference among the risks for any of these anti-Parkinson drugs causing daytime somnolence.     

The clinical and laboratory assessment of the sleepy child

Excessive sleepiness is defined as sleepiness that occurs in a situation when an individual would usually be expected to be awake and alert. Hypersomnia is characterized by recurrent episodes of excessive daytime sleepiness (EDS) or prolonged nighttime sleep, which affects the everyday life of the patient. Clinical surveys have reported that EDS is a complaint observed in up to 68% of normal high school children, with a negative impact in academic achievement and extracurricular activity. Clues toward recognizing childhood daytime sleepiness may be sleeping longer hours than expected for age, daytime naps beyond normal for age, being sleepy when other children of the same age are active and alert, and sleeping more than previously. Causes of EDS are arbitrarily divided into 3 categories: insufficient nighttime sleep, fragmented nighttime sleep, and increased drive of sleep. A list of various causes of EDS in children has been discussed. A detailed history along with examination of the upper airway is crucial in evaluating patients with EDS. Appropriate screening tools such as sleep logs, sleepiness scales, and sleep questionnaires further help in identifying and quantifying the degree of sleepiness. Confirmatory tests such as polysomnography, multiple sleep latency test, and actigraphy along with referral to a sleep physician may be necessary in appropriate cases. Details of other ancillary testing such use of cerebrospinal fluid orexin levels, HLA subtyping, and so on have also been provided.     

The association between disease severity and sleep-related problems in patients with Parkinson's disease

Although sleep-related problems are a frequent finding in patients with Parkinson's disease (PD), the aetiology is still unknown. We examined the associations between disease severity, sleep-related problems and social status in 116 PD patients participating in the FAQT Study, a prospective, German cohort study evaluating determinants of quality of life in PD patients. 47.4% of the patients reported sleep onset difficulties, 26.7% sleep interruptions, 14.7% had five or more sleep-related events during the night and 71.6% showed symptoms of increased daytime somnolence. The disease severity was significantly associated with sleep-related events (p = 0.01), the depression score with sleep onset difficulties (p = 0.04), sleep interruptions (p = 0.01) and the levodopa dose (p < 0.01). We conclude that depressive symptoms and increasing levodopa doses in PD patients mainly cause sleep onset difficulties and sleep interruptions, while the severity of motor symptoms contributes to sleep-related events like sleep walking, heavy sweating and nightmares.     

Sleep episodes and daytime somnolence as result of individual susceptibility to different dopaminergic drugs in a PD patient: a polysomnographic study

The association between excessive daytime somnolence (EDS) and idiopathic Parkinson's disease (PD) is often reported but still debated. The possible role of antiparkinsonian therapy or primarily of PD on excessive diurnal sleepiness is controversial.We describe the case of a 61-year-old patient affected by PD who experienced sleep episodes (SE) occurring during pramipexole plus l-Dopa therapy. Polysomnographic sleep studies and subjective evaluations of daytime sleepiness (Epworth Sleepiness Scale) were carried out under administration of pramipexole plus l-Dopa, l-Dopa monotherapy and cabergoline plus l-Dopa. The polysomnography revealed two sleep events during pramipexole plus l-Dopa. Moreover, the polysomnographic data showed an increase of both diurnal and nocturnal sleep under pramipexole plus l-Dopa compared with cabergoline plus l-Dopa and l-Dopa as monotherapy. In addition, while Epworth Sleepiness Scale (ESS) Score showed a mild sleepiness under pramipexole (ESS score=11), ESS scores were normal under both l-Dopa and cabergoline plus l-Dopa. Sleep episodes also disappeared under both l-Dopa and cabergoline plus l-Dopa (2- and 12-month follow-up). We hypothesize that an individual susceptibility to specific antiparkinsonian drug may play a significant role in the genesis of sleepiness in our PD patient.     

Effect of cabergoline added to levodopa treatment on sleep-wake cycle in idiopathic Parkinson’s disease: an open label 24-hour polysomnographic study

Summary. Few studies focused on the effects of cabergoline on sleep-wake cycle in PD. Twelve patients affected by PD treated with levodopa as monotherapy underwent two 24-hour ambulatory polysomnographic (A-PSG) sessions twice: in baseline condition (levodopa as monotherapy) and after addition of cabergoline. In each condition, a subjective evaluation of sleep quality and daytime sleepiness was obtained by means of Parkinson’s disease Sleep Scale (PDSS) and the Epworth Sleepiness Scale. The statistical analysis of sleep parameters revealed a significant increase of sleep efficiency and slow wave sleep under cabergoline. The PDSS total score showed a significant improvement of overall sleep quality after cabergoline. No significant changes in daytime sleepiness were observed. No patient referred and/or showed sleep attacks before and after addition of cabergoline. We hypothesize that the long-lasting effect of cabergoline may improve the objective quality of nocturnal sleep in PD patients complaining nocturnal motor disability without inducing daytime sleepiness.     

Sleep disturbances in patients with parkinsonism

Altered sleep and vigilance are among the most frequent symptoms, besides parkinsonism, in movement disorders. As many as 60% of patients with Parkinson's disease (PD) experience insomnia, 15-59% show rapid eye movement (REM) sleep behavior disorders (RBDs), and 30% show excessive daytime sleepiness. Insomnia is a distressing difficulty to maintain sleep, which is exacerbated by motor disability, painful dystonia, restless legs, dysuria, anxiety and depressed mood. Improving night-time motor control by overnight treatment with levodopa, transdermal or long-acting dopamine agonists, or bilateral subthalamus stimulation, can improve sleep continuity. RBDs are violent, enacted dreams that expose the patient or their sleeping partner to night-time injuries. A striking improvement of parkinsonism is observed during these behaviors in PD. RBDs are thought to be caused by lesions in the REM sleep atonia system, and can, in association with other early markers of neurodegenerative diseases, such as olfactory, cognitive and autonomic disturbances, precede parkinsonism by several years. Daytime sleepiness, often with a narcolepsy-like phenotype, is a common occurrence in PD, owing to lesions in the arousal systems of the brain. The use of dopamine agonists increases the risk of sleep attacks, especially when driving, suggesting a drug-disease interaction.     

Sleep disturbance and daytime sleepiness in patients with cirrhosis: a case control study

Sleep disturbance and excessive daytime sleepiness have been reported in patients with hepatic cirrhosis. The objective of this study was to evaluate daytime somnolence and sleep complaints in a group of 178 patients with cirrhosis compared to a control group. Sleep features and excessive daytime sleepiness were evaluated by the Basic Nordic Sleep Questionnaire (BNSQ) and the Epworth Sleepiness Scale (ESS). We collected clinical and laboratory data, neurological assessment and EEG recordings in cirrhotic patients. Patients with cirrhosis complained of more daytime sleepiness (p<0.005), sleeping badly at least three times a week (p<0.005), difficulties falling asleep (p<0.01) and frequent nocturnal awakening (p<0.005) than controls. We found a poor correlation between sleep disorders and clinical or laboratory parameters. Our results confirm previous literature reports suggesting a high prevalence of sleep disturbance in patients with cirrhosis. Insomnia and daytime sleepiness are the main complaints. Sleep disorders are probably a multifactorial phenomenon.     

Parkinson's disease and sleep

Sleep disorders are common in Parkinson's disease (PD), as almost two thirds of PD patients report them. From a clinical point of view, they can be classified into disorders of initiation and maintenance of sleep (DIMS), parasomnias, and excessive daytime sleepiness (EDS). Among the causes of DIMS are degenerative changes in the CNS affecting centers for sleep regulation, persistence into the night of daytime PD-related symptoms, concomitant medical or psychiatric disease, disruption of circadian rhythms, and effects of dopaminergic (and other) medication on sleep regulation. Parasomnias might further contribute to sleep disturbance, as they can be accompanied by motor desinhibition during REM sleep. Parasomnias can precede by several years the presence of daytime PD symptoms. EDS has been over the last years the focus of attention for both sleep and movement disorders specialists, due to the fact that it might predispose to traffic accidents. However, the so-called "sleep attacks" never occur without preexisting somnolence. Thus, a careful sleep history can be helpful to determine which patients are exposed to suffer them. Although EDS was initially attributed to the effects of dopaminergic medication, it seems likely that several disease-related factors might also play an important role. An adequate education of the PD patients in sleep hygiene measures and a skilled use of the medication seem necessary to prevent sleep disturbance.     

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.