Sleep Medicine 14 (2013) 1317–1322
Contents lists available at ScienceDirect
Sleep Medicine journal homepage: www.elsevier.com/locate/sleep
Original Article
The effect of childhood obstructive sleep apnea on ambulatory blood pressure is modulated by the distribution of respiratory events during rapid eye movement and nonrapid eye movement sleep Chun Ting Au a,⇑, Crover Kwok Wah Ho b, Yun Kwok Wing b, Albert Martin Li a a b
Department of Pediatrics, Prince of Wales and Shatin Hospitals, The Chinese University of Hong Kong, Shatin, Hong Kong Department of Psychiatry, Prince of Wales and Shatin Hospitals, The Chinese University of Hong Kong, Shatin, Hong Kong
a r t i c l e
i n f o
Article history: Received 7 March 2013 Received in revised form 29 August 2013 Accepted 1 September 2013 Available online 17 October 2013 Keywords: Obstructive sleep apnea Rapid eye movement REM-related OSA Blood pressure Polysomnography Children
a b s t r a c t Objective: We aimed to investigate if different childhood obstructive sleep apnea (OSA) subtypes, namely rapid eye movement (REM)-related, nonrapid eye movement (NREM)-related and stage-independent OSA would exert different effects on ambulatory blood pressure (ABP). Methods: Data from our previous school-based cross-sectional study were reanalyzed. Subjects who had an obstructive apnea–hypopnea index (OAHI) between 1 and 10 events per hour and a total REM sleep duration of >30 min were included in our analysis. REM-related and NREM-related OSA were defined as a ratio of OAHI in REM sleep (OAHIREM) to OAHI in NREM sleep (OAHINREM) of >2 and 5 events per hour, was associated with a higher risk for nocturnal hypertension, whereas the effect of mild OSA was only modest [4]. It has been found that obstructive respiratory events more commonly are found in rapid eye movement (REM) sleep [6,7] in children with OSA, possibly attributed to the reduced muscle tone and blunted arousal and ventilatory responses during this sleep state [6–9]. A previous study revealed that 55% of obstructive apneas in children occurred during REM sleep [10]. Patients with obstructive respiratory events mainly during REM sleep are defined as ⇑ Corresponding author. Tel.: +852 2632 2917; fax: +852 2636 0020. E-mail address: [email protected] (C.T. Au). 1389-9457/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.sleep.2013.09.017
having REM-related OSA. Clinically, the diagnosis of REM-related OSA has not been standardized. For research purposes, a subject is classified as having REM-related OSA when the diagnostic criteria of OSA are fulfilled and the ratio of OAHI in REM sleep (OAHIREM) to OAHI in non-REM (NREM) sleep (OAHINREM) is >2 [11–13]. Although REM-related OSA in children is common, research in this topic is limited. There are no published data on its prevalence based on a community sample. A pediatric study [14] that involved sleep laboratory attendants showed that nearly 70% of patients had higher OAHIREM than OAHINREM. From adult studies, the prevalence of REM-related OSA is approximately 10–36% among patients with OSA [11–13,15]. The clinical significance of REM-related OSA is controversial. Some studies suggest that REM-related OSA is associated with excessive daytime sleepiness [16,11,17], and others argue that the main correlate with adverse outcomes is OAHINREM rather than OAHIREM [18–20]. There currently is no evidence to suggest differential effects on 24-h ambulatory BP (ABP) monitoring by the different OSA subtypes. Our study aimed to investigate if differences in ABP were present in children with OSA, with different
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C.T. Au et al. / Sleep Medicine 14 (2013) 1317–1322
distributions of respiratory events among REM and NREM sleep. We stratified the study population into mild (OAHI, 1–5 events/ h) and moderate OSA (OAHI, 5–10 events/h) subgroups to control for the effect of overall OSA severity on ABP. 2. Methods 2.1. Study design
The other subjects with a ratio between 0.5 and 2 were classified as stage-independent OSA. To avoid an overestimated OAHIREM in cases with inadequate total REM sleep, subjects with less than 30 min of total REM sleep were excluded. The severe OSA cases also were excluded, as there were only three subjects in each of NREM-related and the stage-independent groups. Such small sample size would provide unreliable results. Moreover, their OAHI widely varied from 11.3 events per hour to 80.9 events per hour and combining severe and moderate groups was not an option as that would distort the results by greatly increasing the variance of OAHI.
Data from our previous school-based cross-sectional study, which investigated the association between OSA and ABP, were reanalyzed [4]. The study included 306 children aged 6–13 years recruited from primary schools that were randomly selected from two local districts, Sha Tin and Tai Po. All subjects underwent anthropometric measurements, overnight polysomnography (PSG) and ABP monitoring. ABP monitoring was performed over a 24-h period during which overnight PSG also was performed. Body mass index (BMI) was converted to BMI z score according to normal reference [21]. Written informed consent and assent were obtained from parents and subjects, respectively. The study was approved by the Joint Chinese University of Hong Kong, New Territories East Cluster.
Overnight PSG was performed in a dedicated sleep laboratory with CNS 1000P polygraph (CNS, Inc., Chanhassen MN) as described in our previous publication [22]. All computerized sleep data were further manually edited by experienced PSG technologists and clinicians according to standardized criteria [23]. All studies were standardized to record the time in bed for 9.5 h ± 5 min, starting at 21:30 ± 15 min and ending at 7:00 ± 15 min the next day.
2.2. Clinical research ethics committee
2.4. ABP monitoring
Based on the PSG results, subjects were divided into four groups: (1) healthy control subjects without OSA (OAHI 10 events/h) [4]. In our retrospective analysis subjects within each group, except for the control group, were further stratified into different OSA subtypes, namely REM-related, NREM-related, and stage-independent OSA for comparisons. REM-related OSA and NREM-related OSA were defined as OAHIREM/OAHINREM of >2 and
Contents lists available at ScienceDirect
Sleep Medicine journal homepage: www.elsevier.com/locate/sleep
Original Article
The effect of childhood obstructive sleep apnea on ambulatory blood pressure is modulated by the distribution of respiratory events during rapid eye movement and nonrapid eye movement sleep Chun Ting Au a,⇑, Crover Kwok Wah Ho b, Yun Kwok Wing b, Albert Martin Li a a b
Department of Pediatrics, Prince of Wales and Shatin Hospitals, The Chinese University of Hong Kong, Shatin, Hong Kong Department of Psychiatry, Prince of Wales and Shatin Hospitals, The Chinese University of Hong Kong, Shatin, Hong Kong
a r t i c l e
i n f o
Article history: Received 7 March 2013 Received in revised form 29 August 2013 Accepted 1 September 2013 Available online 17 October 2013 Keywords: Obstructive sleep apnea Rapid eye movement REM-related OSA Blood pressure Polysomnography Children
a b s t r a c t Objective: We aimed to investigate if different childhood obstructive sleep apnea (OSA) subtypes, namely rapid eye movement (REM)-related, nonrapid eye movement (NREM)-related and stage-independent OSA would exert different effects on ambulatory blood pressure (ABP). Methods: Data from our previous school-based cross-sectional study were reanalyzed. Subjects who had an obstructive apnea–hypopnea index (OAHI) between 1 and 10 events per hour and a total REM sleep duration of >30 min were included in our analysis. REM-related and NREM-related OSA were defined as a ratio of OAHI in REM sleep (OAHIREM) to OAHI in NREM sleep (OAHINREM) of >2 and 5 events per hour, was associated with a higher risk for nocturnal hypertension, whereas the effect of mild OSA was only modest [4]. It has been found that obstructive respiratory events more commonly are found in rapid eye movement (REM) sleep [6,7] in children with OSA, possibly attributed to the reduced muscle tone and blunted arousal and ventilatory responses during this sleep state [6–9]. A previous study revealed that 55% of obstructive apneas in children occurred during REM sleep [10]. Patients with obstructive respiratory events mainly during REM sleep are defined as ⇑ Corresponding author. Tel.: +852 2632 2917; fax: +852 2636 0020. E-mail address: [email protected] (C.T. Au). 1389-9457/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.sleep.2013.09.017
having REM-related OSA. Clinically, the diagnosis of REM-related OSA has not been standardized. For research purposes, a subject is classified as having REM-related OSA when the diagnostic criteria of OSA are fulfilled and the ratio of OAHI in REM sleep (OAHIREM) to OAHI in non-REM (NREM) sleep (OAHINREM) is >2 [11–13]. Although REM-related OSA in children is common, research in this topic is limited. There are no published data on its prevalence based on a community sample. A pediatric study [14] that involved sleep laboratory attendants showed that nearly 70% of patients had higher OAHIREM than OAHINREM. From adult studies, the prevalence of REM-related OSA is approximately 10–36% among patients with OSA [11–13,15]. The clinical significance of REM-related OSA is controversial. Some studies suggest that REM-related OSA is associated with excessive daytime sleepiness [16,11,17], and others argue that the main correlate with adverse outcomes is OAHINREM rather than OAHIREM [18–20]. There currently is no evidence to suggest differential effects on 24-h ambulatory BP (ABP) monitoring by the different OSA subtypes. Our study aimed to investigate if differences in ABP were present in children with OSA, with different
1318
C.T. Au et al. / Sleep Medicine 14 (2013) 1317–1322
distributions of respiratory events among REM and NREM sleep. We stratified the study population into mild (OAHI, 1–5 events/ h) and moderate OSA (OAHI, 5–10 events/h) subgroups to control for the effect of overall OSA severity on ABP. 2. Methods 2.1. Study design
The other subjects with a ratio between 0.5 and 2 were classified as stage-independent OSA. To avoid an overestimated OAHIREM in cases with inadequate total REM sleep, subjects with less than 30 min of total REM sleep were excluded. The severe OSA cases also were excluded, as there were only three subjects in each of NREM-related and the stage-independent groups. Such small sample size would provide unreliable results. Moreover, their OAHI widely varied from 11.3 events per hour to 80.9 events per hour and combining severe and moderate groups was not an option as that would distort the results by greatly increasing the variance of OAHI.
Data from our previous school-based cross-sectional study, which investigated the association between OSA and ABP, were reanalyzed [4]. The study included 306 children aged 6–13 years recruited from primary schools that were randomly selected from two local districts, Sha Tin and Tai Po. All subjects underwent anthropometric measurements, overnight polysomnography (PSG) and ABP monitoring. ABP monitoring was performed over a 24-h period during which overnight PSG also was performed. Body mass index (BMI) was converted to BMI z score according to normal reference [21]. Written informed consent and assent were obtained from parents and subjects, respectively. The study was approved by the Joint Chinese University of Hong Kong, New Territories East Cluster.
Overnight PSG was performed in a dedicated sleep laboratory with CNS 1000P polygraph (CNS, Inc., Chanhassen MN) as described in our previous publication [22]. All computerized sleep data were further manually edited by experienced PSG technologists and clinicians according to standardized criteria [23]. All studies were standardized to record the time in bed for 9.5 h ± 5 min, starting at 21:30 ± 15 min and ending at 7:00 ± 15 min the next day.
2.2. Clinical research ethics committee
2.4. ABP monitoring
Based on the PSG results, subjects were divided into four groups: (1) healthy control subjects without OSA (OAHI 10 events/h) [4]. In our retrospective analysis subjects within each group, except for the control group, were further stratified into different OSA subtypes, namely REM-related, NREM-related, and stage-independent OSA for comparisons. REM-related OSA and NREM-related OSA were defined as OAHIREM/OAHINREM of >2 and
