Clinically relevant cut-off values for the Parkinson's Disease Sleep Scale-2 (PDSS-2): a validation study

doi:10.1016/j.sleep.2016.06.026

Sleep Medicine

Volume 24, August 2016, Pages 87-92

https://doi.org/10.1016/j.sleep.2016.06.026 Get rights and content

Highlights

•
Nocturnal disturbances are an important part of non-motor symptoms in Parkinson's disease (PD).
•
A PDSS-2 total score ≥18 may provide a cut-off value that could be used in routine clinical practice.
•
This score can help identify clinically relevant/severe PD-specific sleep problems.

Abstract

Background

Sleep disturbances are a major problem encountered by neurologists attending Parkinson's disease (PD) patients. The Parkinson's Disease Sleep Scale-2 (PDSS-2) assesses a wide spectrum of disease-specific sleep problems and is easy to administer as a patient self-rating scale. The validation study showed that the scale is reliable, valid, and precise. Until now, however, only one Japanese study has assessed cut-off scores to define poor sleepers.

Objectives

In this context we aimed to determine the PDSS-2 cut-off values that define a sleep disturbance severe enough to require referral of the patient to a sleep center or the need for specific treatment.

Methods

Inpatients with idiopathic PD consecutively admitted to our hospital were enrolled. Patients completed the PDSS-2. The attending physician, who was blinded to the PDSS-2 results, but familiar with the patients' history and current disease status, completed a questionnaire consisting of two general questions on the presence of PD-specific and non-PD related sleep problems. Statistical analysis was performed to determine cut-off values for the PDSS-2 and correlation with the physician's evaluation of sleep disturbance severity. A natural cohort of non-PD patients with sleep disorders represented the control group.

Results

The sample consisted of 52 (56%) men and 41 (44%) women with an average age of 69.22 ± 8.74 years. PDSS-2 showed a sensitivity of 77.6% and a specificity of 74.3% in relation to physician's evaluation of PD-specific sleep problems. According to the physician's evaluation, PD-specific sleep disturbances occurred in 62% of the patients. 83% of patients with PDSS-2 scores ≥18 had clinically relevant sleep disturbances compared to only 33% of PD patients with scores <18. The severity of PD-specific sleep problems was well correlated with the PDSS-2 total score (r = 0.49).

Conclusions

To our knowledge, this is the first study to define PDSS-2 cut-off values for the severity of sleep disturbances in a European PD sample. Our study shows that scores ≥18 define clinically relevant PD-specific sleep disturbances.

Introduction

Sleep disturbances are estimated to occur in 60–98% of Parkinson's disease (PD) patients [1], [2], [3]. There are a large variety of sleep disturbances observed in PD patients, but those that occur more frequently than in healthy age-matched subjects include insomnia, sleep fragmentation, rapid eye movement (REM) sleep behavior disorder (RBD), nocturnal akinesia, restless legs syndrome (RLS), and nocturia [4]. Nocturnal disturbances are an important part of non-motor symptoms in PD [5] and are a major problem encountered by neurologists and general practitioners treating PD patients.

The gold standard for the objective assessment of sleep problems in PD patients is video-polysomnography (PSG). However, this examination is both expensive and time-consuming and requires a specialized hospital-based setting, which is not always readily available [6]. Therefore, clinical interviews and sleep scales are frequently used to evaluate sleep disturbances in this population.

A detailed interview with patients and/or their caregivers is often necessary in order to specifically describe the sleep problem and ascertain its degree of severity. Time limitations ensure that questionnaires are the tool of choice for detecting sleep problems in everyday clinical practice. To date, six scales are recommended or suggested by the Movement Disorder Society for assessment of sleep in PD [6]. The Parkinson's Disease Sleep Scale, (PDSS) [7], the Pittsburgh Sleep Quality Index (PSQI) [8], [9], the Scales for Outcomes in Parkinson's Disease (SCOPA-Sleep scale (SCOPA) [10], the Epworth Sleepiness Scale (ESS) [11], the Inappropriate Sleep Composite Score (ISCS) [12], and the Stanford Sleepiness Scale (SSS) [13]. The PDSS-2 is the revised version of the PDSS and was validated in 2010 [14]. The visual analog scale was transformed into a frequency measure for easier use by patients or in clinical studies. The PDSS-2 consists of 15 questions about various sleep and nocturnal disturbances which are rated by patients using one of five response categories ranging from zero (never) to four (very frequent), with a total score ranging from zero (no disturbance) to 60 (maximum nocturnal disturbance). The scale can be divided into three different domains that reflect the complexity of sleep problems in PD [14]: first, nocturnal motor symptoms such as akinesia, early morning dystonia, tremor during waking period at night, periodic limb movements (PLM), restless behavior or immobility (questions four, five, 12, 13), and motor symptoms probably due to RBD (question six); second, PD-specific nocturnal symptoms like hallucinations, confusion states, pain, muscle cramps, difficulties in breathing with snoring, and immobility (questions 7, 9, 10, 11, 15); and third, sleep-specific disturbances like insomnia, sleep maintenance, unrestored sleep in the morning, getting up at night to pass urine, and the overall subjective quality of sleep (questions 1, 2, 3, 8, 14). In the validation study PDSS-2 was shown to be a reliable, valid, precise, and potentially treatment-responsive tool for measuring nocturnal disabilities and sleep disorders in PD [14].

The PDSS-2 is often used in clinical practice, but cut-off values for a European population are missing, leaving some uncertainties in the interpretation of results by general neurologists or general practitioners. It is also of clinical importance to determine a severity cut-off score at which patients should be referred to a sleep specialist or a sleep laboratory. To our knowledge, there is only one published study from Japan, in which the authors tried to determine PDSS-2 cut-off scores [15].

The aim of the study presented here was to define cut-off values for the PDSS-2 scale in a European PD population, and to determine the score at which nocturnal problem is considered clinically significant and requires treatment.

Section snippets

Patients

106 PD inpatients consecutively admitted to our Movement Disorders Clinic (Paracelsus Elena Hospital Kassel) during a three-month period were included in this study. Key inclusion criteria were: Parkinson's disease defined according to UK Brain Bank Criteria, Hoehn and Yahr stages 1–4, and the ability to understand and fill out the PDSS-2. Patients received their usual anti-Parkinson medication or any other medication as necessary, including sleep-specific medications. Those who were proven to

Results

Of the 106 patients, four patients were diagnosed with dementia during hospitalization and were excluded from the study. Nine patients who were found to suffer from an atypical Parkinson syndrome were also excluded. The remaining 93 PD patients fulfilled the inclusion criteria and were enrolled in the study. The group consisted of 41 (44.0%) females and 52 (56.0%) males, with a mean age of 69.22 ± 8.74 years. PD patients' clinical characteristics are presented in Table 1.

According to the

Discussion

The present study determined a cut-off value for the PDSS-2, which defines a clinically relevant sleep problem which is severe enough to be recalled as such by attending nurses and physicians. A PDSS-2 total score ≥18 may provide a cut-off value that could be used in routine clinical practice to differentiate between mild and clinically relevant, moderate to severe sleep disorders in PD patients. This may allow physicians to better evaluate if a PD patient suffers from a clinically relevant and

Funding sources

No funding was received for this study.

Conflict of interest

The authors have no conflicts of interest to report.

The ICMJE Uniform Disclosure Form for Potential Conflicts of Interest associated with this article can be viewed by clicking on the following link: http://dx.doi.org/10.1016/j.sleep.2016.06.026.

. ICMJE Form for Disclosure of Potential Conflicts of Interest form.

Acknowledgment

The authors would like to thank Anne-Marie Williams for her help with editing.

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Original ArticleClinically relevant cut-off values for the Parkinson's Disease Sleep Scale-2 (PDSS-2): a validation study

Highlights

Abstract

Background

Objectives

Methods

Results

Conclusions

Introduction

Section snippets

Patients

Results

Discussion

Funding sources

Conflict of interest

Acknowledgment

Parkinsonism Relat Disord

J Neurol Sci

Psychiatry Res

A community-based study of sleep disorders in patients with Parkinson's disease

Mov Disord

Sleep disorders in Parkinson's disease

Clin Cornerstone

Sleep and fatigue in Parkinson's disease

Parkinsonism Relat Disord

Sleep in Parkinson's disease

J Psychosom Res

Scales to assess sleep impairment in Parkinson's disease: critique and recommendations

Mov Disord

Original Article
Clinically relevant cut-off values for the Parkinson's Disease Sleep Scale-2 (PDSS-2): a validation study