Evaluation of Sleep Quality and Fatigue in Patients with Usher Syndrome Type 2a

Abstract

Purpose: To study the prevalence, level, and nature of sleep problems and fatigue experienced by Usher syndrome type 2a (USH2a) patients.

Design: Cross-sectional study.

Participants: Fifty-six genetically confirmed Dutch patients with syndromic USH2a and 120 healthy controls.

Methods: Sleep quality, prevalence, and type of sleep disorders, chronotype, fatigue, and daytime sleepiness were assessed using 5 questionnaires: (1) Pittsburgh Sleep Quality Index, (2) Holland Sleep Disorders Questionnaire, (3) Morningness-Eveningness Questionnaire, (4) Checklist Individual Strength, and (5) Epworth Sleepiness Scale. For a subset of patients, recent data on visual function were used to study the potential correlation between the outcomes of the questionnaires and disease progression.

Main outcome measures: Results of all questionnaires were compared between USH2a and control cohorts, and the scores of the patients were compared with disease progression defined by age, visual field size, and visual acuity.

Results: Compared with the control population, patients with USH2a experienced a poorer quality of sleep, a higher incidence of sleep disorders, and higher levels of fatigue and daytime sleepiness. Intriguingly, the sleep disturbances and high levels of fatigue were not correlated with the level of visual impairment. These results are in accordance with the patients' experiences that their sleep problems already existed before the onset of vision loss.

Conclusions: This study demonstrates a high prevalence of fatigue and poor sleep quality experienced by patients with USH2a. Recognition of sleep problems as a comorbidity of Usher syndrome would be a first step toward improved patient care. The absence of a relationship between the level of visual impairment and the severity of reported sleep problems is suggestive of an extraretinal origin of the sleep disturbances.

Financial disclosures: Proprietary or commercial disclosure may be found after the references.

Keywords: Fatigue; Questionnaires; Sleep; USH2a; Usher syndrome.

Figure 1

Sleep quality and efficiency based on the Pittsburgh Sleep Quality Index (PSQI) questionnaire. A, Global PSQI scores. The black horizontal line indicates the cutoff value for poor sleep quality. B, Parameters for sleep efficiency. All individual participant scores are shown as dots. Boxes show first to third quartile, in which the black horizontal line indicates the median. Whiskers extend to the most extreme data point in the 1.5 interquartile range. Scores were compared with the Wilcoxon rank-sum test (∗P < 0.05; ∗∗P < 0.01; ∗∗∗P < 0.001). USH = Usher syndrome.

Figure 2

Percentage of participants using medication to help them sleep. Assessed by the Pittsburgh Sleep Quality Index question “During the past month, how often have you taken medication (prescribed or over the counter) to help you sleep?” Green, not during the past month; Yellow, less than once a week; Orange, once or twice a week; Red, ≥ 3 times a week. Number of participants with or without medication were compared with a chi-square test of homogeneity (∗P < 0.05). USH = Usher syndrome.

Figure 3

Prevalence of sleep disorders as assessed with the Holland Sleep Disorders Questionnaire (HSDQ). Black horizontal lines indicate cutoff value for sleep disorders. General HSDQ scores were compared with the Wilcoxon rank-sum test (∗∗∗∗P < 0.0001). CRSWD = circadian rhythm sleep–wake disorder; SBD = sleep-related breathing disorders; SRMD = sleep-related movement disorders; USH2a = Usher syndrome type 2a.

Figure 4

Chronotype distribution based on the Morningness–Eveningness Questionnaire (MEQ). Control population is shown in blue; patient population is shown in red. No significant difference in chronotype was found between both groups (Kolmogorov–Smirnov test; D = 0.1292; P = 0.55). Scores 16 to 30 indicate definite evening types, 31 to 41 indicate moderate evening types, 42 to 58 indicate intermediate chronotypes, 59 to 69 indicate moderate morning types, and 70 to 86 indicate definite morning chronotypes. Dotted lines represent the mean MEQ score of both groups.

Figure 5

Levels of fatigue as assessed by the Checklist Individual Strength (CIS). A, Global CIS scores. Black horizontal line indicates the cutoff value for problematic fatigue. B, Scores for the dimension “subjective experience of fatigue.” Black horizontal lines indicate the cutoff values for abnormal (score > 26) or severe fatigue (score > 35). Absolute scores were compared with the Wilcoxon rank-sum test (∗∗∗P < 0.001; ∗∗∗∗P < 0.0001). USH = Usher syndrome.

Figure 7

Epworth Sleepiness Scale score representing daytime sleepiness. All individual participant scores are shown as dots. The black horizontal line indicates the cutoff value for excessive daytime sleepiness. Absolute scores were compared with the Wilcoxon rank-sum test (∗∗∗P < 0.001). ESS = Epworth Sleepiness Scale; USH2a = Usher syndrome type 2a.

Figure 12

Pittsburgh Sleep Quality Index, Holland Sleep Disorder Questionnaire (HSQDQ), Checklist Individual Strength (CIS), and Epworth Sleepiness Scale (ESS) scores plotted against age. Red and blue lines represent regression lines of the patient and control population, respectively. Individual participants are shown as dots. Black horizontal lines represent the cutoff values for problematic fatigue/sleep. PSQI = Pittsburgh Sleep Quality Index.

Figure 13

Pittsburgh Sleep Quality Index, Holland Sleep Disorder Questionnaire (HSDQ), Checklist Individual Strength (CIS), and Epworth Sleepiness Scale (ESS) scores plotted against visual field. Visual field was shown as the average mean deviation (MD) of both eyes (n = 20). Red line represents regression line. PSQI = Pittsburgh Sleep Quality Index.