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Deep Venous Thrombosis Attributed to Sleep Apnea
LETTER
Deep Venous Thrombosis Attributed to Sleep Apnea To the Editor: I read with interest the findings reported by Chou et al1 in “Sleep Apnea and Risk of Deep Vein Thrombosis: A Nonrandomized, Pair-matched Cohort Study.” This study used a matched-pair cohort design that examined the effects of sleep apnea on subsequent deep vein thrombosis. The authors demonstrate an increased risk of deep venous thrombosis in patients with sleep apnea who were using the continuous positive airway pressure. Although these results demonstrate the relative risk of sleep apnea on deep vein thrombosis, these measures of effect are limited in their ability to assess how much of deep vein thrombosis risk is indeed attributed to sleep apnea. Using the data from this pair-matched cohort study (Table 1), I calculated the attributable risk and found that the excess occurrence of deep vein thrombosis attributed to obstructive sleep apnea is 3 cases per 1000 patients with obstructive sleep apnea. To interpret, if we eliminate obstructive sleep apnea in 1000 patients, we prevent 3 cases of deep vein thrombosis. This translates to 60% of deep vein thrombosis that can be prevented among patients with obstructive sleep apnea if they are treated (attributable risk percent). Several chronic conditions, including obesity, are associated with increased deep vein thrombosis risk. Obesity (body mass index >30 kg/m2) is associated with a 2- to 3-fold increased risk of venous thromboembolism.2,3 Several studies have demonstrated the strong association of obstructive sleep apnea with obesity.4,5 Therefore, it is difficult to determine whether the increased deep vein thrombosis risk was due to sleep apnea or obesity. The authors appropriately acknowledge this limitation. In fact, if data on obesity were examined, the results of the study might have been different. As indicated, it is prudent for the physician to have knowledge of other important risk factors, such as obesity, daytime sleepiness, immobility, and time spent in bed, that are present in
Funding: None. Conflict of Interest: None. Authorship: Both authors had access to the data and played a role in writing this manuscript.
0002-9343/$ -see front matter Ó 2013 Elsevier Inc. All rights reserved.
Table 1
Study Data
Sleep apnea Control
DVT
No DVT
30 10 40
5456 4285 9741
5486 4295 9781 (total)
DVT ¼ deep vein thrombosis.
association with obstructive sleep apnea and thus can be managed to decrease the sequential risk of deep vein thrombosis. The attributable risk percent shows that 60% of deep vein thrombosis can be prevented in patients with obstructive sleep apnea who receive the treatment with continuous positive airway pressure, which is significant. Therefore, it is important to address the various risk factors that are associated with deep vein thrombosis, including sleep apnea, and to appropriately intervene in and manage patients with obstructive sleep apnea. Nazia Naz S. Khan, MDa M. Safwan Badr, MD, MBAb a
Department of Internal Medicine Wayne State University Detroit, Mich b Pulmonary Critical Care and Sleep Medicine Department of Internal Medicine, Harper University Hospital Wayne State University School of Medicine Detroit, Mich
http://dx.doi.org/10.1016/j.amjmed.2013.01.027
References 1. Chou KT, Huang CC, Chen YM, et al. Sleep apnea and risk of deep vein thrombosis: a non-randomized, pair-matched cohort study. Am J Med. 2012;125:374-380. 2. Tsai AW, Cushman M, Rosamond WD, Heckbert SR, Polak JF, Folsom AR. Cardiovascular risk factors and venous thromboembolism incidence: the longitudinal investigation of thromboembolism etiology. Arch Intern Med. 2002;162:118-129. 3. Stein PD, Beemath A, Olson RE. Obesity as a risk factor in venous thromboembolism. Am J Med. 2005;118:978-980. 4. Vgontzas AN, Bixler EO, Chrousos GP. Metabolic disturbances in obesity versus sleep apnoea: the importance of visceral obesity and insulin resistance. J Intern Med. 2003;254:32-44. 5. Punjabi NM, O’Hearn DJ, Neubauer DN, et al. Modeling hypersomnolence in sleep-disordered breathing. Am J Respir Crit Care Med. 1999;159:1703-1709.
Deep Venous Thrombosis Attributed to Sleep Apnea To the Editor: I read with interest the findings reported by Chou et al1 in “Sleep Apnea and Risk of Deep Vein Thrombosis: A Nonrandomized, Pair-matched Cohort Study.” This study used a matched-pair cohort design that examined the effects of sleep apnea on subsequent deep vein thrombosis. The authors demonstrate an increased risk of deep venous thrombosis in patients with sleep apnea who were using the continuous positive airway pressure. Although these results demonstrate the relative risk of sleep apnea on deep vein thrombosis, these measures of effect are limited in their ability to assess how much of deep vein thrombosis risk is indeed attributed to sleep apnea. Using the data from this pair-matched cohort study (Table 1), I calculated the attributable risk and found that the excess occurrence of deep vein thrombosis attributed to obstructive sleep apnea is 3 cases per 1000 patients with obstructive sleep apnea. To interpret, if we eliminate obstructive sleep apnea in 1000 patients, we prevent 3 cases of deep vein thrombosis. This translates to 60% of deep vein thrombosis that can be prevented among patients with obstructive sleep apnea if they are treated (attributable risk percent). Several chronic conditions, including obesity, are associated with increased deep vein thrombosis risk. Obesity (body mass index >30 kg/m2) is associated with a 2- to 3-fold increased risk of venous thromboembolism.2,3 Several studies have demonstrated the strong association of obstructive sleep apnea with obesity.4,5 Therefore, it is difficult to determine whether the increased deep vein thrombosis risk was due to sleep apnea or obesity. The authors appropriately acknowledge this limitation. In fact, if data on obesity were examined, the results of the study might have been different. As indicated, it is prudent for the physician to have knowledge of other important risk factors, such as obesity, daytime sleepiness, immobility, and time spent in bed, that are present in
Funding: None. Conflict of Interest: None. Authorship: Both authors had access to the data and played a role in writing this manuscript.
0002-9343/$ -see front matter Ó 2013 Elsevier Inc. All rights reserved.
Table 1
Study Data
Sleep apnea Control
DVT
No DVT
30 10 40
5456 4285 9741
5486 4295 9781 (total)
DVT ¼ deep vein thrombosis.
association with obstructive sleep apnea and thus can be managed to decrease the sequential risk of deep vein thrombosis. The attributable risk percent shows that 60% of deep vein thrombosis can be prevented in patients with obstructive sleep apnea who receive the treatment with continuous positive airway pressure, which is significant. Therefore, it is important to address the various risk factors that are associated with deep vein thrombosis, including sleep apnea, and to appropriately intervene in and manage patients with obstructive sleep apnea. Nazia Naz S. Khan, MDa M. Safwan Badr, MD, MBAb a
Department of Internal Medicine Wayne State University Detroit, Mich b Pulmonary Critical Care and Sleep Medicine Department of Internal Medicine, Harper University Hospital Wayne State University School of Medicine Detroit, Mich
http://dx.doi.org/10.1016/j.amjmed.2013.01.027
References 1. Chou KT, Huang CC, Chen YM, et al. Sleep apnea and risk of deep vein thrombosis: a non-randomized, pair-matched cohort study. Am J Med. 2012;125:374-380. 2. Tsai AW, Cushman M, Rosamond WD, Heckbert SR, Polak JF, Folsom AR. Cardiovascular risk factors and venous thromboembolism incidence: the longitudinal investigation of thromboembolism etiology. Arch Intern Med. 2002;162:118-129. 3. Stein PD, Beemath A, Olson RE. Obesity as a risk factor in venous thromboembolism. Am J Med. 2005;118:978-980. 4. Vgontzas AN, Bixler EO, Chrousos GP. Metabolic disturbances in obesity versus sleep apnoea: the importance of visceral obesity and insulin resistance. J Intern Med. 2003;254:32-44. 5. Punjabi NM, O’Hearn DJ, Neubauer DN, et al. Modeling hypersomnolence in sleep-disordered breathing. Am J Respir Crit Care Med. 1999;159:1703-1709.