pii: jc- 00122-16http://dx.doi.org/10.5664/jcsm.5780
CO MMEN TA RY
Can You Hear Me Now?
Commentary on Chopra et al. Sleep apnea is associated with hearing impairment: the Hispanic Community Health Study/Study of Latinos. J Clin Sleep Med 2016;12(5):719–726 and Seo et al. Lowest oxyhemoglobin saturation may be an independent factor influencing auditory function in severe obstructive sleep apnea. J Clin Sleep Med 2016;12(5):653–658. Amir Sharafkhaneh, MD, PhD1,2; Max Hirshkowitz, PhD3 Department of Medicine, Section of Pulmonary, Critical Care and Sleep Medicine, Baylor College of Medicine, Houston, TX; 2Medical Care Line, Section of Pulmonary, Critical Care and Sleep Medicine, Michael E. DeBakey VA Medical Center, Houston, TX; 3Consulting Professor, Division of Public Mental Health and Population Sciences, School of Medicine, Stanford University, Stanford, CA
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In this issue of Journal of Clinical Sleep Medicine, two studies report on association between sleep apnea and hearing impairment. Chopra and colleagues present data associating hearing impairment and sleep apnea in a large population of individuals from Hispanic descent.1 The study clearly shows a relationship between hearing impairment and sleep apnea. The authors also discuss possible pathophysiologic mechanism(s) linking sleep apnea to hearing impairment. The second study by Seo and colleagues shows that in a small sample of patients with severe sleep apnea (defined as AHI > 30 per hour of sleep), nadir oxygen saturation during the sleep study was associated with higher risk of hearing impairment.2 Snoring has been proposed as a cause of hearing impairment (HI) in obstructive sleep apnea (OSA). However, data supporting such a relationship are mixed.3,4 The study by Chopra failed to show any additional effect for snoring beyond OSA on HI.1 Nonetheless, exposure to loud sounds is known to adversely affect hearing to the extent that regulations exist regarding exposure to loud sounds in the workplace.5 Objective measures showed that noise due to snoring sometimes exceed work place noise limits.6 Importantly, however, snoring noise in OSA occurs in the milieu of hypoxia. Even if snoring alone does not result in HI, effects of simultaneous presence of snoring sound and hypoxia is not clear. Various studies suggest hypoxia and ischemia as the common pathway for various insults to cause HI.7 Intense sound diminishes cochlear perilymph oxygenation and causes accumulation of hypoxia inducible factor 1 (HIF-1) in the inner ear.8,9 In a rodent model, presence of hypoxia potentiate effect of noise on producing hearing loss.10 So the jury is still out on the effect of snoring in patients with OSA and significant hypoxia. One interesting and important result of Chopra’s and Seo’s studies is the association between hypoxia and HI. In Chopra’s study, 44.7%, 42%, and 48% of all OSA, moderate OSA and severe OSA, respectively, had HI. Interestingly, the highest prevalence of HI (according to quartiles of hypoxia) was 52.5% in patients with SpO2 below 85.2% (Table S1 in the supplemental material). For all the other quartiles of SpO2 (above 85.2%) the prevalence of HI is much lower than what was found in OSA
categories as mentioned above. In Seo’s study, subjects with hearing impairment had significantly lower nadir oxyhemoglobin saturations. Thus, data provide strong support that severity of hypoxia is the main culprit linking OSA to HI. The other possible mechanism linking OSA to HI involves changes in intracranial perfusion due to sleep apnea.11 It is known that increased intracranial pressure can present with hearing impairment.12,13 Auditory evoked potentials are disturbed with higher centers more affected than the lower hearing center (cochlea).14 An even more complex issue in sleep apnea is the effect of acute nightly change in intracranial pressure versus chronic changes in intracranial pressure that may happen in patients with OSA over years. The comorbid illnesses associated with OSA can also contribute to HI. Hypertension, diabetes mellitus, and dyslipidemia are risk factors associated with hearing impairment.15 Obesity is a prevalent risk factor and comorbid condition in patients with OSA. The question may therefore relate more to an obesity threshold, obesity’s relative contribution to HI beyond effects of snoring, and hypoxia. An animal study showed that weight gain activated hypoxia-induced factor 1 (HIF-1) and resulted in blood vessels with smaller diameters and thicker walls in the stria vascularis and increased inflammatory response at the middle and basal turns of the cochlea, with reduced cell densities in the spiral ganglion and spiral ligament at the cochlea.16 Both studies in this issue of the journal took a further step in adjusting for presence of vascular risk factors and BMI showing that only severe OSA is associated with increased odds of having HI. The study by Chopra and colleagues showed a clear association between the HI and OSA with an even stronger association between severity of hypoxia and HI (Table S1 in the supplemental material). It also showed that the population studied may be different than a normal healthy population, as a quarter of the population has oxygen saturations below 85%. The study by Seo and colleagues provided additional evidence for relationship between hypoxia and HI. More data on association between hypoxia (for example length of time below 88%) and HI may help further elucidate the link. In addition, 641
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A Sharafkhaneh and M Hirshkowitz. Commentary
as snoring was not measured objectively, the effect of various levels of snoring on HI is not clear from this study, especially when snoring occurs during hypoxic episodes. Clinically, the paramount question is how these data will improve care for our patients in day-to-day practice. The studies point to a potentially modifiable risk factor for HI. Although the studies did not aim at and evaluated effects of treatment of OSA on HI, a next logical step would be to assess such effects.
8. Scheibe F, Haupt H, Ludwig C. Intensity-dependent changes in oxygenation of cochlear perilymph during acoustic exposure. Hear Res 1992;63:19–25. 9. Chung JW, Kang HH, Shin JE, Kim JU. Accumulation of hypoxia-inducible factor-1alpha in mouse inner ear by noise stimulation. Neuroreport 2004;15:2353–6. 10. Chen GD, Liu Y. Mechanisms of noise-induced hearing loss potentiation by hypoxia. Hear Res 2005;200:1–9. 11. Wardly DE. Intracranial hypertension associated with obstructive sleep apnea: a discussion of potential etiologic factors. Med Hypotheses 2014;83:792–7. 12. Sismanis A. Otologic manifestations of benign intracranial hypertension syndrome: diagnosis and management. Laryngoscope 1987;97:1–17. 13. Hansen CC. Perceptive hearing loss and increased intracranial pressure. Arch Otolaryngol 1968;87:45–7. 14. Matsuura S, Kuno M, Nakamura T. Intracranial pressure and auditory evoked responses of the cat. Acta Otolaryngol 1986;102:12–9. 15. Van EE, Van CG, Van LL. The complexity of age-related hearing impairment: contributing environmental and genetic factors. Audiol Neurootol 2007;12:345–58. 16. Hwang JH, Hsu CJ, Yu WH, Liu TC, Yang WS. Diet-induced obesity exacerbates auditory degeneration via hypoxia, inflammation, and apoptosis signaling pathways in CD/1 mice. PLoS One 2013;8:e60730.
C I TAT I O N Sharafkhaneh A, Hirshkowitz M. Can you hear me now? J Clin Sleep Med 2016;12(5):641–642. R E FE R E N CES 1. Chopra A, Jung M, Kaplan RC, et al. Sleep apnea is associated with hearing impairment: the Hispanic Community Health Study/Study of Latinos. J Clin Sleep Med 2016;12:719–26. 2. Seo YJ, Park SY, Chung HJ, et al. Lowest oxyhemoglobin saturation may be an independent factor influencing auditory function in severe obstructive sleep apnea. J Clin Sleep Med 2016;12:653–8. 3. Prazic M. Snoring and presbyacusis. Acta Otolaryngol 1973;75:216–9. 4. Hoffstein V, Haight J, Cole P, Zamel N. Does snoring contribute to presbycusis? Am J Respir Crit Care Med 1999;159:1351–4. 5. Occupational Noise Exposure; Standard 1910.95. OSAH. 2016. Occupational Safety and Health Standards. 2-12-2016. 6. Wilson K, Stoohs RA, Mulrooney TF, Johnson LJ, Guilleminault C, Huang Z. The snoring spectrum: acoustic assessment of snoring sound intensity in 1,139 individuals undergoing polysomnography. Chest 1999;115:762–70. 7. Mazurek B, H. Haupt H, Georgiewa P, Klapp BF, Reisshauer A. A model of peripherally developing hearing loss and tinnitus based on the role of hypoxia and ischemia. Med Hypotheses 2006;67:892–99.
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SUBM I SSI O N & CO R R ESPO NDENCE I NFO R M ATI O N Submitted for publication March, 2016 Accepted for publication March, 2016 Address correspondence to: Amir Sharafkhaneh, MD, PhD, 2002 Holcombe Blvd., Houston, Texas 77030; Tel: (713) 794-7318; Fax: (713) 794-7558; Email:
[email protected]
D I SCLO S U R E S TAT E M E N T The authors have indicated no financial conflicts of interest. This work is supported by the office of Research and Development at the Department of Veterans Affairs.
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