CORRESPONDENCE Arrigo Capitanio, M.D. Mary Falzon, M.D. University College London London, United Kingdom Bernadette Carroll, B.Sc. Neal Navani, M.D. University College London Hospitals London, United Kingdom James Brown, M.D. Ricky M. Thakrar, M.D. University College London London, United Kingdom Philip Jeremy George, M.D. University College London Hospitals London, United Kingdom Ashley M. Groves, M.D.* Sam M. Janes, M.D.* University College London London, United Kingdom *A.M.G. and S.M.J. contributed equally.

References 1. Jemal A, Siegel R, Ward E, Hao Y, Xu J, Thun MJ. Cancer statistics, 2009. CA Cancer J Clin 2009;59:225–249. 2. Jeremy George P, Banerjee AK, Read CA, O’Sullivan C, Falzon M, Pezzella F, Nicholson AG, Shaw P, Laurent G, Rabbitts PH. Surveillance for the detection of early lung cancer in patients with bronchial dysplasia. Thorax 2007;62:43–50. 3. Wisnivesky JP, Yung RC, Mathur PN, Zulueta JJ. Diagnosis and treatment of bronchial intraepithelial neoplasia and early lung cancer of the central airways: diagnosis and management of lung cancer, 3rd ed: American College of Chest Physicians evidence-based clinical practice guidelines. Chest 2013;143: e263S–e277S. 4. Lam S, Macaulay C, Leriche JC, Ikeda N, Palcic B. Early localization of bronchogenic carcinoma. Diagn Ther Endosc 1994;1:75–78. 5. Aristizabal JF, Young KR, Nath H. Can chest CT decrease the use of preoperative bronchoscopy in the evaluation of suspected bronchogenic carcinoma? Chest 1998;113:1244–1249. 6. Donckier JE, Roelants V, Pochet JM. Staging of non-small-cell lung cancer with positron-emission tomography. N Engl J Med 2000;343: 1572. [Author reply 1572–1573.] 7. Pipinikas CP, Kiropoulos TS, Teixeira VH, Brown JM, Varanou A, Falzon M, Capitanio A, Bottoms SE, Carroll B, Navani N, et al. Cell migration leads to spatially distinct but clonally related airway cancer precursors. Thorax 2014;69:548–557. 8. Bota S, Auliac JB, Paris C, Metayer ´ J, Sesbou¨ e´ R, Nouvet G, Thiberville L. Follow-up of bronchial precancerous lesions and carcinoma in situ using fluorescence endoscopy. Am J Respir Crit Care Med 2001;164: 1688–1693. 9. Vallieres ` E, Van Houtte P, Travis WD, Rami-Porta R, Goldstraw P; International Association for the Study of Lung Cancer (IASLC) International Staging Committee. Carcinoma in situ at the bronchial resection margin: a review. J Thorac Oncol 2011;6:1617–1623. 10. Pasic A, Brokx HA, Comans EF, Herder GJ, Risse EK, Hoekstra OS, Postmus PE, Sutedja TG. Detection and staging of preinvasive lesions and occult lung cancer in the central airways with 18F-fluorodeoxyglucose positron emission tomography: a pilot study. Clin Cancer Res 2005;11:6186–6189. 11. Ohtani K, Lee AM, Lam S. Frontiers in bronchoscopic imaging. Respirology 2012;17:261–269.

Copyright © 2016 by the American Thoracic Society

Correspondence

Obstructive Sleep Apnea, Sleep Duration, and Fasting Glucose To the Editor: Bakker and colleagues reported that there is a significant association between obstructive sleep apnea (OSA) and fasting glucose only in specific races (1). In contrast, sleep duration was not significantly associated with fasting glucose. The authors classified sleep duration into three groups by using Actiwatch Spectrum (Philips Respironics, Murrysville, PA), OSA into three groups according to the apnea–hypopnea index by sleep polysomnography, and fasting glucose into two groups by defining abnormal fasting glucose as >100 mg/dl and/or hypoglycemic medication use. I have some concerns about their study. First, Twedt and colleagues reported the relationship between sleep duration by Actiwatch Spectrum and blood glucose in women with gestational diabetes mellitus (2). Fasting blood glucose and 1-hour postprandial blood glucose concentrations after breakfast, lunch, and dinner were measured, and significant increases in each blood glucose level were observed in subjects with sleep duration less than 5 hours by adjusting age, gestational age, and body mass index. Although Twedt and colleagues handled a limited number of patients, I suppose that short sleep duration, which was measured by Actiwatch Spectrum, was a risk of abnormal blood glucose not only in fasting state but also in three situations of 1-hour postprandial states after breakfast, lunch, and dinner. Although the statistical significance between sleep duration and abnormal fasting glucose in the article by Bakker and colleagues disappeared by additionally adjusting for the apnea–hypopnea index, I think there is room for further study before making a final conclusion. Second, the authors monitored sleep duration by sleep polysomnography and Actiwatch Spectrum. The authors used sleep duration by Actiwatch Spectrum to check data in habitual daily life and cited their article on the procedure of measurement (3). Unfortunately, the authors did not present their selection of threshold as the sleep/wake cutoff point. Medium threshold (40 counts per minute) is initially set as the standard cutoff value, but there was overestimation of sleep duration and underestimation of wake after sleep onset by selecting the standard cutoff value (4). According to Table 1 in the article by Bakker and colleagues, there are about 30 minutes of difference in sleep duration between these methods. As Bakker and colleagues have 2,151 samples of sleep duration by sleep polysomnography and Actiwatch Spectrum, I recommend the authors present validation data in their study. Third, the authors set reference sleep duration from 5 to 8 hours, but the same research group (3) selected sleep duration from 7 to 8 hours as the reference by citing two articles (5, 6). Are there any reasons for selecting a reference group with a wide range of sleep duration? Finally, factors affecting mental health should also be selected as adjusting variables. OSA is closely related to depression, in addition to hypertension, stroke, and diabetes (7), and the biological mechanisms between OSA and metabolic disorders should also be considered with psychosocial interactions. n

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CORRESPONDENCE

Author disclosures are available with the text of this letter at www.atsjournals.org.

Author disclosures are available with the text of this letter at www.atsjournals.org.

Tomoyuki Kawada, M.D., Ph.D. Nippon Medical School Tokyo, Japan

Ze-Zhou Song, M.S. Zhejiang Provincial People’s Hospital Hangzhou, China

References

References 1. Bakker JP, Weng J, Wang R, Redline S, Punjabi NM, Patel SR; The MultiEthnic Study of Atherosclerosis. Associations between obstructive sleep apnea, sleep duration, and abnormal fasting glucose. Am J Respir Crit Care Med 2015;192:745–753. 2. Twedt R, Bradley M, Deiseroth D, Althouse A, Facco F. Sleep duration and blood glucose control in women with gestational diabetes mellitus. Obstet Gynecol 2015;126:326–331. 3. Chen X, Wang R, Zee P, Lutsey PL, Javaheri S, Alcantara ´ C, Jackson CL, Williams MA, Redline S. Racial/ethnic differences in sleep disturbances: the multi-ethnic study of atherosclerosis (MESA). Sleep 2015;38:877–888. 4. Peterson BT, Chiao P, Pickering E, Freeman J, Zammit GK, Ding Y, Badura LL. Comparison of actigraphy and polysomnography to assess effects of zolpidem in a clinical research unit. Sleep Med 2012; 13:419–424. 5. Grandner MA, Hale L, Moore M, Patel NP. Mortality associated with short sleep duration: the evidence, the possible mechanisms, and the future. Sleep Med Rev 2010;14:191–203. 6. Jackson CL, Redline S, Kawachi I, Williams MA, Hu FB. Racial disparities in short sleep duration by occupation and industry. Am J Epidemiol 2013;178:1442–1451. 7. Eastwood PR, Malhotra A, Palmer LJ, Kezirian EJ, Horner RL, Ip MS, Thurnheer R, Antic NA, Hillman DR. Obstructive sleep apnoea: from pathogenesis to treatment. Current controversies and future directions. Respirology 2010;15:587–595.

Copyright © 2016 by the American Thoracic Society

The Impact of Obesity on the Association between Obstructive Sleep Apnea and Glucose Metabolism To the Editor: It was with great interest that I read the article by Bakker and colleagues (1), which concluded that obstructive sleep apnea (OSA) is independently associated with glucose metabolism and that this association may vary by ethnicity. It is well known that OSA in nonobese individuals is significantly associated with impaired glucose metabolism; however, OSA is not associated with abnormal glucose tolerance categories (2). That is to say, the association of OSA with glucose metabolism is different between obese and nonobese individuals. In the study by Bakker and colleagues (1), the differences in the association of OSA with glucose metabolism between obese and nonobese individuals were ignored. As in the study by Bakker and colleagues (1), some individuals with OSA are not obese, especially those of Asian descent (3). Therefore, further studies should be performed to confirm the differences of the association of OSA with glucose metabolism between obese and nonobese individuals and whether this association could vary by ethnicity. n

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1. Bakker JP, Weng J, Wang R, Redline S, Punjabi NM, Patel SR; The Multi-Ethnic Study of Atherosclerosis. Associations between obstructive sleep apnea, sleep duration, and abnormal fasting glucose. Am J Respir Crit Care Med 2015;192: 745–753. 2. Kim NH, Cho NH, Yun CH, Lee SK, Yoon DW, Cho HJ, Ahn JH, Seo JA, Kim SG, Choi KM, et al. Association of obstructive sleep apnea and glucose metabolism in subjects with or without obesity. Diabetes Care 2013;36: 3909–3915. 3. Lin QC, Zhang XB, Chen GP, Huang DY, Din HB, Tang AZ. Obstructive sleep apnea syndrome is associated with some components of metabolic syndrome in nonobese adults. Sleep Breath 2012;16: 571–578.

Copyright © 2016 by the American Thoracic Society

Reply From the Authors: Dr. Kawada expresses concern about our use of actigraphy to quantify habitual sleep duration (1). We did use the medium threshold (40 counts per epoch) to differentiate wake from sleep. Prior studies have not found clear benefits in terms of agreement with polysomnography by using either a higher or lower threshold in adults (2, 3). Although actigraphy is known to underestimate wake after sleep onset as a result of scoring of quiet wakefulness as sleep, there is little evidence to suggest this offset leads to systematic bias. In particular, a prior study found similar performance of actigraphy in quantifying sleep in those with and without sleep apnea (4). Dr. Kawada is also concerned by our categorization of sleep duration. The decision to define short sleep duration as

Obstructive Sleep Apnea, Sleep Duration, and Fasting Glucose.

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