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. 2013 Nov 21;8(11):e81233.
doi: 10.1371/journal.pone.0081233. eCollection 2013.

Objective measurement of daytime napping, cognitive dysfunction and subjective sleepiness in Parkinson's disease

Samuel J Bolitho  1 , Sharon L Naismith, Pierre Salahuddin, Zoe Terpening, Ron R Grunstein, Simon J G Lewis
Affiliations

Objective measurement of daytime napping, cognitive dysfunction and subjective sleepiness in Parkinson's disease

Samuel J Bolitho et al. PLoS One. .

Abstract

Introduction: Sleep-wake disturbances and concomitant cognitive dysfunction in Parkinson's disease (PD) contribute significantly to morbidity in patients and their carers. Subjectively reported daytime sleep disturbance is observed in over half of all patients with PD and has been linked to executive cognitive dysfunction. The current study used daytime actigraphy, a novel objective measure of napping and related this to neuropsychological performance in a sample of PD patients and healthy, age and gender-matched controls. Furthermore this study aimed to identify patients with PD who may benefit from pharmacologic and behavioural intervention to improve these symptoms.

Methods: Eighty-five PD patients and 21 healthy, age-matched controls completed 14 days of wrist actigraphy within two weeks of neuropsychological testing. Objective napping measures were derived from actigraphy using a standardised protocol and subjective daytime sleepiness was recorded by the previously validated Epworth Sleepiness Scale.

Results: Patients with PD had a 225% increase in the mean nap time per day (minutes) as recorded by actigraphy compared to age matched controls (39.2 ± 35.2 vs. 11.5 ± 11.0 minutes respectively, p < 0.001). Significantly, differences in napping duration between patients, as recorded by actigraphy were not distinguished by their ratings on the subjective measurement of excessive daytime sleepiness. Finally, those patients with excessive daytime napping showed greater cognitive deficits in the domains of attention, semantic verbal fluency and processing speed.

Conclusion: This study confirms increased levels of napping in PD, a finding that is concordant with subjective reports. However, subjective self-report measures of excessive daytime sleepiness do not robustly identify excessive napping in PD. Fronto-subcortical cognitive dysfunction was observed in those patients who napped excessively. Furthermore, this study suggests that daytime actigraphy, a non-invasive and inexpensive objective measure of daytime sleep, can identify patients with PD who may benefit from pharmacologic and behavioural interventions to improve these symptoms.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Average nap time per day (minutes).
A chart depicting the average nap time per day (± standard error) calculated by summing the daytime napping periods identified by actigraphy and averaging this over the 14 day measurement period. Panel A - Parkinson’s disease vs. Controls. Panel B - Parkinson’s disease patients divided into those who are Epworth Sleepiness Scale positive (score ≥ to 10 indicative of sleepiness) vs. Parkinson’s Disease patients who are Epworth Sleepiness Scale negative.
Figure 2
Figure 2. Cognitive performance of excessive nappers within the Parkinson’s disease cohort.
A chart comparing the cognitive performance (mean ± standard error) of patients with Parkinson’s disease (PD) divided into those with excessive daytime napping vs. those with normal daytime napping. Set shifting was measured with the Trailmaking task part B (TMT B; z score). Semantic verbal fluency (VF) was tested via the Controlled Oral Word Associated Test (COWAT animals; z score) and processing speed was measured with the choice reaction time (RT) test from the Cambridge Neuropsychological Test Automated Battery (CANTAB; z score).
Figure 3
Figure 3. Mood and disease specific variables within the Parkinson’s disease cohort based on subjective sleepiness scores.
A chart that reports depression scores, disease stage and Levodopa dose equivalents (mean ± standard error) when patients with Parkinson’s Disease are divided into those who are Epworth Sleepiness Scale positive (score ≥ to 10 indicative of a positive tendency to sleep during the day) vs. those who are Epworth Sleepiness Scale negative.
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Publication types

Grants and funding

Funding of the study was supported by NHMRC PhD Scholarship and CIRUS (Dr SJB); NHMRC Career Development Award (Associate Professor SLN); NHMRC Practitioner Fellowship (Professor RRG); NHMRC Practitioner Fellowship (Associated Professor SJGL). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.