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. 2024 Feb 6;19(2):e0288216.
doi: 10.1371/journal.pone.0288216. eCollection 2024.

Creation of a shortened version of the Sleep Disorders Questionnaire (SDQ)

Kathleen Biard  1 , Joseph De Koninck  1   2 , Alan B Douglass  2   3
Affiliations

Creation of a shortened version of the Sleep Disorders Questionnaire (SDQ)

Kathleen Biard et al. PLoS One. .

Abstract

The 176-item Sleep Disorders Questionnaire (SDQ) was initially developed using canonical discriminant function analysis on 4 groups of sleep disorder patients, but it was never studied by factor analysis in its entirety. Several authors have criticized 2 of its subscales as being confounded with each other, and its narcolepsy scale as substantially over-diagnosing narcolepsy. This study describes its first exploratory factor analysis (EFA), the intent of which was to reassess item membership on the 4 existing subscales and to derive new scales to improve differential diagnosis between patient groups. It was also hoped that EFA could reduce the total number of questions, to increase speed of completion. The EFA was performed on the anonymized SDQ results from a retrospective review of the charts of 2131 persons from 7 sleep disorders clinics and research centers. Factors were assessed via scree plots and eigenvalues. The EFA identified four main factors: insomnia, daytime sleepiness, substance use, and sleep-disordered breathing. The insomnia factor had 3 subfactors: psychological symptoms of insomnia, subjective description of insomnia, and insomnia due to periodic limb movements. The sleepiness factor had two subfactors: daytime sleepiness and neurological symptoms of narcolepsy. The novel substance use factor was homogeneous, as was the sleep-disordered breathing factor. Importantly, the EFA reassigned items from the original SDQ's NAR, PSY, and PLM subscales to five of the new subscales. The Sleep Apnea (SA) subscale emerged mostly unchanged. The 7 resulting factors comprised only 66 items of the original 176-item SDQ. These results have allowed the creation of a new shorter questionnaire, to be called the SDQ-2. External validation of the SDQ-2 is currently underway. It will likely prove to be a superior differential diagnostic instrument for sleep disorders clinics, compared to the original SDQ.

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Conflict of interest statement

I have read the journal’s policy and the authors of this manuscript have the following competing interests: Drs. Biard and De Koninck declare no competing interests. Dr. Douglass claims copyright of the resulting SDQ-2 questionnaire and may profit from its future commercialization. He is also a paid consultant to the Ottawa Police Association, which is sponsoring a validation study of the SDQ-2. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Figures

Fig 1
Fig 1. Scree plot of all factors extracted by the EFA.
The first 4 factors all have eigenvalues greater than 5, and are referred to as Main Factors in the text.
See this image and copyright information in PMC

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References

    1. Douglass AB, Bornstein R, Nino-Murcia G, Keenan S, Miles L, Zarcone VPJ, et al.. The Sleep Disorders Questionnaire. I: Creation and multivariate structure of SDQ. Sleep. 1994;17(2):160–7. doi: 10.1093/sleep/17.2.160 - DOI - PubMed
    1. Miles LE. The Sleep Questionnaire and Assessment of Wakefulness. In: Guilleminault C, editor. Sleeping and waking disorders, indications and techniques. Menlo Park, CA: Addison-Wesley Pub. Co. Medical/Nursing Division: 1982. p. 383–413.
    1. Douglass AB. Item test-retest reliability of the Sleep Disorders Questionnaire (SDQ). Sleep Research. 1990;19:215.
    1. Buysse DJ, Reynolds Cd, Monk TH, Berman SR, Kupfer DJ. The Pittsburgh Sleep Quality Index: a new instrument for psychiatric practice and research. Psychiatry Res. 1989;28(2):193–213. doi: 10.1016/0165-1781(89)90047-4 - DOI - PubMed
    1. Guichard K, Marti-Soler H, Micoulaud-Franchi JA, Philip P, Marques-Vidal P, Vollenweider P, et al.. The NoSAS score: A new and simple screening tool for obstructive sleep apnea syndrome in depressive disorder. J Affect Disord. 2018;227:136–40. doi: 10.1016/j.jad.2017.10.015 - DOI - PubMed

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