Do Parkinson disease subject and caregiver-reported Epworth sleepiness scale reponses correlate?

Subjective excessive daytime sleepiness, commonly measured with the Epworth Sleepiness Scale (ESS), is associated with cognitive impairment in Parkinson disease (PD). Significant correlation between subject and informant responses has been reported in neurologically healthy individuals. We sought to assess this correlation in patients with PD.

854 individuals in the Arizona Study of Aging and Neurodegenerative Disorders (AZSAND) had subject as well as informant-completed ESS completed within one year of a movement disorder exam and cognitive assessment. Correlations were evaluated using Spearman's rank correlation coefficients.

Overall, 397/854(46.5 %) were female with mean age of 77.5 (SD 8.3). 572 (67 %) were cognitively normal (CogNL), 135 (15.8 %) had mild cognitive impairment (MCI) and 147 (17.2 %) dementia. Spearman R correlations (all with p < 0.001) between subject and informant ESS responses were 0.73 overall, 0.67 for the CogNL group, 0.79 for the MCI group, 0.79 for those with dementia. Of 175 with clinically probable PD, 115 (65.7 %) were CogNL, 38 had MCI, and 22 (12.6 %) dementia. For subjects with PD correlations (all with p < 0.001) were 0.65 for PD-CogNL, 0.83 for PD-MCI, and 0.70 for those with PD-dementia.

These significant correlations between subject and informant-completed ESS can be useful in guiding clinical trials designed to assess efficacy of potential treatments for excessive daytime sleepiness for the general population and for patients with PD, even those having cognitive impairment.