Fatigue and sleepiness determine respiratory quality of life among veterans evaluated for sleep apnea

Vinnikov et al. Health and Quality of Life Outcomes (2017) 15:48 DOI 10.1186/s12955-017-0624-x RESEARCH Open Access Fatigue and sleepiness determine respiratory quality of life among veterans evaluated for sleep apnea Denis Vinnikov1,2* , Paul D. Blanc3,4, Alaena Alilin5, Moshe Zutler6 and Jon-Erik C. Holty5,7,8 Abstract Background: In those with symptoms indicative of obstructive sleep apnea (OSA), respiratory-specific health-related quality of life (HRQL) may be an important patient-centered outcome. The aim of this study was to assess the associations between sleepiness, fatigue, and impaired general and respiratory-specific HRQL among persons with suspected OSA. Methods: We evaluated military veterans consecutively referred for suspected OSA with sleep studies yielding apneahypopnea index (AHI) values. They also completed the sleepiness (Epworth Sleepiness Scale [ESS]), and fatigue (Fatigue Severity Scale [FSS]) questionnaires, as well as two HRQL instruments (the generic Short-Form SF-12v2 yielding the Physical Component Scale [PCS] and the respiratory-specific Airways Questionnaire [AQ]-20R). Multiple linear regression tested the associations between ESS and FSS (standardized as Z scores for scaling comparability) with AQ-20R, accounting for AHI, SF-12v2-PCS and comorbid respiratory conditions other than OSA. Results: We studied 1578 veterans (median age 61.1 [IQR 16.8] years; 93.9% males). Of these, 823 (52%) met AHI criteria for moderate to severe OSA (AHI ≥15/h). The majority reported excessive daytime sleepiness (53%; median ESS 11 [IQR 9]) or fatigue (61%; median FSS 42 [IQR 23]). The median AQ-20R was 4 [IQR 1–8]. Controlling for AHI, SF-12v2-PCS, respiratory co-morbid conditions, body mass index, and demographics, both ESS and FSS were significantly associated with poorer AQ-20R: for each; ESS, 1.6 points (95% CI 1.4–1.9), and for FSS, 2.5 points (95% CI, 2.3–2.7). Conclusions: Greater daytime sleepiness and fatigue are associated with poorer respiratory-specific HRQL, over and above the effects of OSA, respiratory comorbidity, and generic physical HRQL. Keywords: Quality of life, Sleep apnea syndromes, Lung diseases, Disorders of excessive somnolence, Fatigue, Health status indicators, Pulmonary disease, Chronic obstructive, Asthma Background Health-related quality of life (HRQL) is a critical patientcentered outcome measuring generic or disease-specific health status. Disease-specific HRQL is relevant to chronic health conditions whose effects are manifested through discrete subjective symptoms and limitations. Respiratory-specific HRQL is a condition-specific construct emphasizing patient-perceived impacts related to dyspnea and other pulmonary limitations. * Correspondence: 1 Department of Internal Medicine, Occupational Diseases and Hematology, Kyrgyz State Medical Academy, Bishkek, Kyrgyzstan 2 School of Public Health, Al-Farabi Kazakh National University, Almaty, Kazakhstan Full list of author information is available at the end of the article Obstructive sleep apnea (OSA) is a common respiratory condition occurring during sleep that carries substantial morbidity and mortality [1]. Although many OSA patients report symptoms such as snoring, general population and sleep clinic-based studies suggest many do not report excessive daytime sleepiness or fatigue [1–4]. Furthermore, the relationship between OSA and general (and particularly physical) [5–11] as well as respiratory-specific HRQL [12] is less well established. On the other hand, respiratory disorders such as chronic obstructive pulmonary disease (COPD), independent of OSA, are associated with poor subjective and objective sleep quality [13, 14], sleepiness [2] and decreased general and respiratory specific HRQL [15]. Furthermore, sleep disturbance is a major determinant of © The Author(s). 2017 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Vinnikov et al. Health and Quality of Life Outcomes (2017) 15:48 HRQL in those with chronic respiratory disorders such as asthma [16] or COPD [17]. The determinants of respiratory-specific HRQL in OSA (with or without co-morbid lung conditions) remain to be well characterized [12, 18, 19]. Sleepiness and fatigue as HRQL determinants are particularly relevant given they may adversely impact patient-perceived physical and respiratory-specific HRQL status [20–22]. The extent to which OSA, comorbid respiratory disorders, daytime sleepiness and fatigue in combination may contribute to HRQL remains unclear. The aim of this study was to test sleepiness and fatigue as independent predictors of respiratory-specific HRQL among persons with symptoms suggestive of OSA who went on to diagnostic testing. This has been an open question whose answer is relevant clinically to help better gauge the likely impact of OSA diagnosis and treatment on HRQL among symptomatic patients. Our primary hypothesis was that daytime sleepiness and fatigue in this population would be independently associated with respiratory-specific HRQL, taking into account OSA as well as concomitant respiratory disease. Methods This cross-sectional retrospective study of prospectively collected clinical data was undertaken in a cohort of military veterans referred due to OSA symptoms for a standardized assessment protocol that included both a multi-battery questionnaire and confirmatory polysomnography. We intentionally included a respiratoryspecific HRQL measure in the questionnaire so that we could clinically assess breathing problems as well as carry out an analysis with this as our central patientcentered outcome. Study subjects Study participants were referred for OSA assessment based on their symptoms according to routine clinical practice and the potential subject pool comprised all veterans referred to the Veterans Affairs (VA) Palo Alto Healthcare System’s Pulmonary-Sleep Section for evaluation of complaints of either disrupted sleep or snoring who completed formal sleep study testing. Thus, participant accrual was passive: there was no specific recruitment or outreach for the study itself. Data from consecutive subjects aged 21–95 studied from May 2011 through July 2014 were retrospectively analyzed. Subjects were eligible for study inclusion if they completed a structured sleep questionnaire and an overnight diagnostic sleep study. Exclusion criteria included: incomplete or missing questionnaire or inadequate sleep study data; evidence of a physiolog (...truncated)