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Response from the authors
Sleep Medicine 8 (2007) 787 www.elsevier.com/locate/sleep
Letters to the Editor Prevalence and time-course of sleep-disordered breathing in patients with acute coronary syndrome To the Editor I read with interest the article by Mehra and colleagues who reported a high prevalence of sleep-disordered breathing (SDB) in patients with acute coronary syndrome (ACS) [1]. I noticed that the authors did not exclude conditions that may increase the prevalence of SDB and desaturation, such as patients who were on sedation or narcotics, alcoholics, and patients with chronic obstructive pulmonary disease (COPD) or stroke. Furthermore, they did not comment on sleep position and did not address the fact that patients are more likely to lie supine in the coronary care unit (CCU) setting compared to their own home, which may increase the apnea–hypopnea index (AHI). In a recently published paper, we reported the prevalence and time-course of SDB in 50 consecutive patients with ACS after excluding the above conditions that may affect SDB [2]. All patients underwent full overnight polysomnography (PSG) in the CCU 3.1 ± 2.4 days after the acute event. A repeat PSG in the sleep laboratory was done 6 months later for patients with AHI > 10/h to assess the time-course of SDB and to control for the possible effect of supine sleep position in the CCU. Fifty-six percent of the studied group had an AHI > 10/h, 44% had an AHI > 20/h and 34% had an AHI > 30/h. In concurrence with Mehra et al. [1], we found no difference in outcome between patients with SDB and patients without SDB. Additionally, a multivariate regression analysis failed to detect any predictors of an AHI > 10/h. Mehra et al. [1] raised the possibility that the acute physiologic changes associated with ACS may result in overestimation of the baseline degree of apnea. To explore this possibility, we repeated PSG in the sleep laboratory 6 months after the acute event. Interestingly, AHI, obstructive apnea index and the mean duration of obstructive apneas did not change significantly over the 6 months. On the other hand, central apnea index and central apnea duration were significantly lower in the second assessment.
References [1] Mehra R, Principe-Rodriguez K, Kirchner HL, Strohl KP. Sleep apnea in acute coronary syndrome: high prevalence but low impact on 6-month outcome. Sleep Med 2006;7:521–8. [2] BaHammam A, Al-Mobeireek A, Al-Nozha M, Al-Tahan A, Bin Saeed A. Behavior and time-course of sleep disordered breathing in patients with acute coronary syndromes. Int J Clin Pract 2005;59:874–80.
Ahmed S. BaHammam King Saud University, Riyadh 11324, Saudi Arabia E-mail address: [email protected] 1389-9457/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.sleep.2007.01.002
Response from the authors We appreciate the comments of Dr. BaHammam. Prevalence is defined as the proportion of individuals found to have a condition at a certain point in time (number of existing cases/population at risk during a specified time period). As one of our aims was to address the prevalence of sleep-disordered breathing (SDB) in a VA sample with acute coronary syndrome (ACS), we did not exclude conditions that would increase the prevalence of SDB, as this would not provide an accurate reflection of the true prevalence of SDB in those individuals presenting with ACS and would limit generalizability of our findings to VA populations, which are typically enriched with comorbidity. While we agree that patients in the intensive care unit setting are more likely to sleep in the supine position, we also recognize that supine sleep time is encouraged during clinical sleep studies in order to provide optimal likelihood of capturing the respiratory disturbance. We did not impose any restriction on body position during the sleep study. Reena Mehra * Kingman P. Strohl E-mail address: [email protected] (R. Mehra). *
Corresponding author. 1389-9457/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.sleep.2007.01.001
Letters to the Editor Prevalence and time-course of sleep-disordered breathing in patients with acute coronary syndrome To the Editor I read with interest the article by Mehra and colleagues who reported a high prevalence of sleep-disordered breathing (SDB) in patients with acute coronary syndrome (ACS) [1]. I noticed that the authors did not exclude conditions that may increase the prevalence of SDB and desaturation, such as patients who were on sedation or narcotics, alcoholics, and patients with chronic obstructive pulmonary disease (COPD) or stroke. Furthermore, they did not comment on sleep position and did not address the fact that patients are more likely to lie supine in the coronary care unit (CCU) setting compared to their own home, which may increase the apnea–hypopnea index (AHI). In a recently published paper, we reported the prevalence and time-course of SDB in 50 consecutive patients with ACS after excluding the above conditions that may affect SDB [2]. All patients underwent full overnight polysomnography (PSG) in the CCU 3.1 ± 2.4 days after the acute event. A repeat PSG in the sleep laboratory was done 6 months later for patients with AHI > 10/h to assess the time-course of SDB and to control for the possible effect of supine sleep position in the CCU. Fifty-six percent of the studied group had an AHI > 10/h, 44% had an AHI > 20/h and 34% had an AHI > 30/h. In concurrence with Mehra et al. [1], we found no difference in outcome between patients with SDB and patients without SDB. Additionally, a multivariate regression analysis failed to detect any predictors of an AHI > 10/h. Mehra et al. [1] raised the possibility that the acute physiologic changes associated with ACS may result in overestimation of the baseline degree of apnea. To explore this possibility, we repeated PSG in the sleep laboratory 6 months after the acute event. Interestingly, AHI, obstructive apnea index and the mean duration of obstructive apneas did not change significantly over the 6 months. On the other hand, central apnea index and central apnea duration were significantly lower in the second assessment.
References [1] Mehra R, Principe-Rodriguez K, Kirchner HL, Strohl KP. Sleep apnea in acute coronary syndrome: high prevalence but low impact on 6-month outcome. Sleep Med 2006;7:521–8. [2] BaHammam A, Al-Mobeireek A, Al-Nozha M, Al-Tahan A, Bin Saeed A. Behavior and time-course of sleep disordered breathing in patients with acute coronary syndromes. Int J Clin Pract 2005;59:874–80.
Ahmed S. BaHammam King Saud University, Riyadh 11324, Saudi Arabia E-mail address: [email protected] 1389-9457/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.sleep.2007.01.002
Response from the authors We appreciate the comments of Dr. BaHammam. Prevalence is defined as the proportion of individuals found to have a condition at a certain point in time (number of existing cases/population at risk during a specified time period). As one of our aims was to address the prevalence of sleep-disordered breathing (SDB) in a VA sample with acute coronary syndrome (ACS), we did not exclude conditions that would increase the prevalence of SDB, as this would not provide an accurate reflection of the true prevalence of SDB in those individuals presenting with ACS and would limit generalizability of our findings to VA populations, which are typically enriched with comorbidity. While we agree that patients in the intensive care unit setting are more likely to sleep in the supine position, we also recognize that supine sleep time is encouraged during clinical sleep studies in order to provide optimal likelihood of capturing the respiratory disturbance. We did not impose any restriction on body position during the sleep study. Reena Mehra * Kingman P. Strohl E-mail address: [email protected] (R. Mehra). *
Corresponding author. 1389-9457/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.sleep.2007.01.001