The validity of the dutch sleep disorders questionnaire (Sdq)

doi:10.1016/S0022-3999(98)00030-0

Journal of Psychosomatic Research

Volume 45, Issue 6, December 1998, Pages 549-555

https://doi.org/10.1016/S0022-3999(98)00030-0 Get rights and content

Abstract

The Sleep Disorders Questionnaire (SDQ) is a 176-item questionnaire designed to diagnose the presence of common sleep disorders. This study set out to assess the validity of a Dutch translation of the SDQ. Scores on 145 questionnaires were analyzed. A cluster analysis of these scores revealed the following clusters: healthy, depression, insomnia, narcolepsy, and apnea. The cluster classification proved correct for 67% of the subjects, as determined on the basis of polysomnography. These results show that the Dutch SDQ is a reasonably valid instrument for diagnosing sleep disorders.

Introduction

The Sleep Disorders Questionnaire (SDQ) [1] is designed for the assessment of common sleep disorders. As a diagnostic tool, it offers an inexpensive and time-saving alternative for more demanding methods such as polysomnography. Published reports of diagnostic questionnaires are scarce. An inventory has been published that is designed to assess the presence of sleep apnea [2]. Many existing instruments such as St. Mary’s Sleep Questionnaire [3] and the Pittsburgh Sleep Quality Index [4] evaluate only the sleep of the previous night. Others are questionnaires for daily symptom ratings, such as the Stanford Sleepiness Scale [5], the Epworth Sleepiness Scale [6], and the Sleep Evaluation Questionnaire [7]. Douglass et al. demonstrated that their questionnaire had good test–retest reliability [8] and was used successfully to support diagnoses in patients suspected of having a sleep disorder [9]. The aim of the present study was to examine the validity of the Dutch translation of the SDQ, which has been used at the Center for Sleep Disorders in The Hague since 1993. To do so, sleep disorder subgroups were formed on the basis of cluster analysis of the questionnaire scores and were compared with a classification based on polysomnography.

Section snippets

Subjects

The SDQ consists of 176 questions (items) that could be answered on a five-point rating scale. A total of 145 questionnaires were analyzed. One hundred twenty-five were filled out by physician-referred patients with several sleep complaints who visited the Westeinde Sleep Disorders Center. The other 20 questionnaires were completed by university workers and students free of sleep complaints as assessed by interview. Participants included 62 women and 83 men. The patients had an average age of

Principal components analysis

The preliminary principal components analysis yielded 26 components with eigenvalue ⩾1. Four of these were considered relevant, because they clearly represent different groups of complaints and could be interpreted in terms of well-known sleep disorders; that is, insomnia (eigenvalue 13.46), narcolepsy (eigenvalue 8.35), sleep apnea (eigenvalue 5.10) and depression (eigenvalue 3.69). The four factors jointly accounted for 34% of the total variance. Table I presents the Varimax-rotated factor

Discussion

The current investigation was conducted to determine whether the shortened Dutch version of the Sleep Disorders Questionnaire is a valid diagnostic instrument. Two thirds of all patients were correctly classified. Consequently, it seems justified to conclude that the SDQ demonstrated fair validity. Among the 25 misclassified patients, 14 patients were incorrectly assigned to the apnea group. On the basis of polysomnography, seven of these were diagnosed as healthy, five as insomniacs, and two

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Original ArticleThe validity of the dutch sleep disorders questionnaire (Sdq)

Abstract

Introduction

Section snippets

Subjects

Principal components analysis

Discussion

Psychiatry Res

Creation of the “ASDC Sleep Disorders Questionnaire”

Sleep Res

Identifying sleep apnea from self reports

Sleep

Factor analysis of the St

Mary’s Hospital Sleep Questionnaire. Sleep

Quantification of sleepiness; a new approach

Psychophysiology

Reliability and factor analysis of the Epworth Sleepiness Scale

Sleep

Original Article
The validity of the dutch sleep disorders questionnaire (Sdq)