Original ArticleSex-specific sleep apnea screening questionnaires: closing the performance gap in women
Introduction
Sleep apnea (SA), characterized by repetitive breathing pauses during sleep, is highly prevalent and often remains undiagnosed [1,2]. The apnea/hypopnea index (AHI), the number of apneas and hypopneas per hour of sleep, is used as the measure for SA diagnosis and its severity. SA is considered to be mild when the AHI is ≥ 5 and <15 per hour of sleep, moderate if the AHI is ≥ 15 and <30 h−1 and severe if the AHI exceeds 30 h−1 [3]. Moderate-to-severe obstructive SA has been related to an increased risk for cardiovascular morbidity and mortality [[4], [5], [6], [7]], and a significant socio-economic burden, and therapeutic options improving outcome are available [[8], [9], [10]].
Attended polysomnography (PSG) is currently the gold standard diagnostic test; moreover, ambulatory cardiorespiratory polygraphy (PG) in the absence of significant comorbidities is an accepted diagnostic test [[11], [12], [13]]. However, limited access to these procedures can result in underdiagnosis or diagnostic delays. Therefore, identifying subjects who benefit from diagnostic testing with poly(somno)graphy [P(S)G] is an important challenge. The most frequently used pre-test screening strategy consists of questionnaires, comprising subjective symptoms and clinical data. The Neck, Obesity, Snoring, Age, Sex (NoSAS) score is a weighted SA screening questionnaire first developed in a community-based cohort [14], and subsequently validated in clinical populations, mainly consisting of sleep clinic patients [[15], [16], [17]]. The STOP-Bang questionnaire (SBQ) was originally developed for SA screening in the pre-operative setting [18,19]. Since the SBQ has mainly been validated in clinical populations, only limited evidence is available on its validity in the general population [[15], [16], [17],[20], [21], [22], [23], [24]]. Both NoSAS and the SBQ have been developed and validated in mixed-sex populations, with the assessment of their diagnostic properties in the overall (men + women) group. Two smaller studies addressed the important sex differences in SA screening tests in bariatric surgery and diabetic populations [16,25]. However, the sex-specific diagnostic performance has not been evaluated in the general population. Notably, the intrinsic questionnaire items gender and neck circumference (NC) are varied in men and women. Furthermore, SA is clearly more prevalent in men than in women [26]. Considering the important sex-differences in SA prevalence, in anthropometry, particularly for NC, and in the clinical presentation of the disease, we hypothesize that there is an important sex difference in the diagnostic performance of NoSAS and the SBQ. The main objective of our study was to calculate the intrinsic (sensitivity, specificity) and derived (positive predictive value, PPV and negative predictive value, NPV) characteristics of NoSAS and the SBQ as SA screening tests in the general population for both sexes separately. Second, we aimed to identify the optimal sex-specific total questionnaire and NC cut-offs for SA screening in women. We assessed the diagnostic performance of the NoSAS and SBQ scores in a large community-dwelling prospective cohort with the AHI obtained from home-based PG.
Section snippets
Population and study design
The study population consisted of the 2252 randomly selected community-dwelling volunteers (aged 42–72 years, 52.3% women) in the second measurement round (2011–2016) of the Asklepios cohort, an ongoing population-based cohort study in two twinned Belgian communities [26,27]. During their visit at the study center, the participants were invited to complete the questionnaires and to undergo home PG. Subjects who were already diagnosed with or treated for SA, were excluded (Fig. 1). During the
Results
Of the 2205 volunteers eligible for PG, 133 (6%) had no registration and 263 (11.9%) recordings were below pre-defined quality criteria. Successful registrations were obtained in 1809 participants (87.3% of recordings) (Fig. 1). Their key descriptive characteristics are shown in Table 1. The mean age was 56.0 ± 5.9 years; 52.3% were women and the mean BMI was 26.8 ± 4.6 kg/m2. The characteristics of the participants with and those without successful PG were comparable (appendix, Table A.1).
Discussion
In contrast to what occurs in males, the NoSAS and the SBQ scores display low sensitivities and high specificities in females, making them less suitable as screening tools for women. Using a sex-specific NoSAS and SBQ reverses this imbalance and achieves test sensitivities in women similar to those in men, whilst still retaining higher specificities and AUCs than in men. Diagnostic performance indices of sleep questionnaires should be reported in a sex-stratified fashion, as results from
Conclusions
In our general population cohort, the NoSAS and SBQ sleep apnea screening tests have an acceptable sensitivity in men. In women however, the low sensitivities make them less suitable for sleep apnea screening. The potential of these useful screening tools can be maximized using sex-specific cut-offs, resulting in an important increase of the sensitivity of the questionnaires in women, reaching the same level as in men, with retained higher specificities and AUCs as in men, and at the
Funding and support
FB received grant support from the Ghent University Hospital Clinical Research Fund (KOF). The Asklepios Study is supported by the Fund for Scientific Research Flanders (FWO research grants G042703 and G083810N). The funding sources did not have any involvement in the study design; in the collection, analysis and interpretation of data; in the writing of the report; or in the decision to submit the article for publication. ERR and JAC have received research support (equipment loans) from ResMed
Acknowledgements
The authors thank the study participants who voluntarily participated in the Asklepios study, the general practitioners of Erpe-Mere and Nieuwerkerken, and Femke Van Hoeke for general secretarial assistance.
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