Polysomnographic Characteristics of a Referred Sample of Children with Sickle Cell Disease
2010; American Academy of Sleep Medicine; Volume: 06; Issue: 04 Linguagem: Inglês
10.5664/jcsm.27880
ISSN1550-9397
AutoresValerie E. Rogers, D Lewin, Glenna B. Winnie, Jeanne Geiger‐Brown,
Tópico(s)Obstructive Sleep Apnea Research
ResumoFree AccessTonsillectomy Polysomnographic Characteristics of a Referred Sample of Children with Sickle Cell Disease Valerie E. Rogers, Ph.D., Daniel S. Lewin, Ph.D., Glenna B. Winnie, M.D., Jeanne Geiger-Brown, Ph.D. Valerie E. Rogers, Ph.D. Address correspondence to: Dr. Valerie E. Rogers, 307D Claire M. Fagin Hall, 418 Curie Boulevard, Philadelphia, PA 19104-4217(215) 746-4447(410) 794-6485(215) 573-7507 E-mail Address: [email protected], or E-mail Address: [email protected] Center for Sleep and Respiratory Neurobiology, Division of Biobehavioral Health Sciences, University of Pennsylvania School of Nursing, Philadelphia, PA , Daniel S. Lewin, Ph.D. Sleep Disorders Medicine, Division of Lung Diseases, NHLBI, Bethesda, MD , Glenna B. Winnie, M.D. The Pediatric Sleep Center of the Pediatric Lung Center, Purcellville, VA , Jeanne Geiger-Brown, Ph.D. Work and Health Research Center, Department of Family and Community Health, University of Maryland School of Nursing, Baltimore, MD Published Online:August 15, 2010https://doi.org/10.5664/jcsm.27880Cited by:55SectionsAbstractPDF ShareShare onFacebookTwitterLinkedInRedditEmail ToolsAdd to favoritesDownload CitationsTrack Citations AboutABSTRACTStudy Objectives:To describe polysomnographic parameters and their clinical correlates in a referred sample of children with sickle cell disease (SCD).Methods:This was a retrospective medical record review of 55 consecutive children aged 2-18 years with SCD (hemoglobin [Hb] SS and Hb SC genotypes) undergoing polysomnography for evaluation of sleep disordered breathing. Polysomnography values were compared between SCD genotypes, 4 age groups, and adenotonsillectomy status using descriptive and nonparametric statistics.Results:Obstructive sleep apnea (OSA) was diagnosed in 38/55 (69%) children. Polysomnographic parameters differed significantly between Hb SS and Hb SC genotypes only on arterial oxyhemoglobin saturation (SpO2; 95.2 ± 3.8 vs. 98.0 ± 0.8, respectively, p < 0.01) and percent of sleep time below SpO2 90% (T90; 8.0 ± 22.0 vs. 0.01 ± 0.02, respectively, p < 0.05). Increasing age was associated with decreasing SpO2 (rho = −0.282, p < 0.05), obstructive apnea-hypopnea index (OAHI; rho = −0.364, p < 0.01), total arousal index (rho = −0.272, p < 0.05) and respiratory arousal index (rho = −0.349, p < 0.01). Periodic limb movements in sleep (PLM) averaged 4.7 ± 8.8/h, with a PLM index > 5/h in 5/17 children without OSA. Post- adenotonsillectomy, 8/10 children had OSA, but compared to untreated OSA-positive children they had a lower mean OAHI (4.4 ± 5.5 vs. 8.9 ± 12.5) and a lower T90 (1.6 ± 4.2 vs. 9.2 ± 24.9).Conclusions:Both OSA and PLMs were common in children with SCD. Children with Hb SS experienced more severe nocturnal oxygen desaturation than did those with Hb SC. Post-adenotonsillectomy, most children had OSA, although they experienced fewer obstructive respiratory events and less severe nocturnal oxygen desaturation than did untreated OSA-positive children.Citation:Rogers VE; Lewin DS; Winnie GB; Geiger-Brown J. Polysomnographic characteristics of a referred sample of children with sickle cell disease. J Clin Sleep Med 2010;6(4):374-381.INTRODUCTIONSleep and sleep disorders in children with sickle cell disease (SCD) have been little explored. Sickle cell disease is the most common genetic disorder in the United States, with approximately 1,000 affected infants born each year.1 In SCD, mutation of the hemoglobin (Hb) molecule (sickle hemoglobin, or Hb S) results in polymerization, or sickling of Hb S under conditions of hypoxemia. Sickling, in turn, contributes to vasoocclusion and hemolysis—events responsible for the high morbidity and mortality associated with SCD.BRIEF SUMMARYCurrent Knowledge/Study Rationale: Little sleep related data has been published on children with sickle cell disease other than overnight pulse oximetry findings. This study aimed to describe full polysomnography findings of a sample of children with sickle cell disease referred for sleep disordered breathing, and to describe differences by genotype, age group and adenotonsillectomy status.Study Impact: This study contributes to the limited literature describing objective sleep using pediatric scoring criteria in this population. It further highlights implications for clinical care and suggests directions for future research in children with sickle cell disease in whom sleep and the impact of sleep disorders has been largely unexplored.Existing evidence suggests that children with SCD are at increased risk of disordered breathing during sleep2 and obstructive sleep apnea (OSA). Excessive adenoidal and tonsillar growth occurs in children with SCD, phenomena attributed to compensatory lymphoid tissue hyperplasia or chronic infection secondary to functional asplenia.3,4 Adenotonsillar hypertrophy presents the main risk factor for obstructive sleep apnea in childhood,5 a disease in which obstructed ventilation results in transient periods of hypoxemia. Thus, adenotonsillar hypertrophy presents an important risk factor for OSA in children with SCD, and hypoxemia during obstructed breathing may pose a risk for erythrocyte sickling. Evidence further suggests that children with SCD experience more severe sleep disordered breathing than unaffected children. A recent case-control study of children with SCD matched on age, gender, and ethnicity to healthy controls demonstrated a four-fold increased risk of nadir oxyhemoglobin saturation below 85%, and a 7-fold increased risk of sleep time spent at an end-expiratory carbon dioxide level greater than 50 mm Hg in children with SCD compared to controls.6Disease-specific normative polysomnography data do not currently exist for children with SCD. Few studies report polysomnography data on these children,6–10 with the exception of overnight pulse oximetry values.11,12 Establishing separate diagnostic polysomnographic criteria may be important, however. Dysfunctional hemoglobins in SCD and a right-shifted oxyhemoglobin dissociation curve alter arterial oxyhemoglobin saturation (SpO2) values measured by pulse oximetry.13–15 Moreover, nearly half of children with SCD experience nocturnal hypoxemia that is not associated with sleep disordered breathing.11,16 These disease-related changes cannot be interpreted as inconsequential or normal, yet they suggest a need for interpreting polysomnography based on disease-specific values.The purpose of the present study was to describe polysomnography values of a sample of children with SCD referred to a sleep laboratory for evaluation of sleep disordered breathing. A secondary aim was to explore the association between objective measures of sleep and clinical variables including SCD genotype, age group, and adenotonsillectomy status. These findings are intended to contribute to the very limited literature using pediatric scoring of polysomnography data in this population. This study was carried out as part of a more comprehensive retrospective study of the relationship of OSA and severity of SCD in children.17METHODSSampleThe sample was a retrospective case series of children with SCD referred to a children's hospital-based sleep laboratory for evaluation of sleep disordered breathing between March 2004 and October 2008. Demographic, clinical, and polysomnographic data were collected from the hospital electronic medical record following approval by the institutional review boards of the Children's National Medical Center and the University of Maryland School of Medicine. Inclusion criteria were ages 2 to 18 years with a diagnosis of Hb SS or Hb SC disease. Subjects were excluded for craniofacial abnormality or neuromuscular disorder, current treatment with positive airway pressure therapy, pregnancy, or illness at the time of the sleep study. Eighty consecutive children were screened, and 55 qualified for inclusion.Diagnostic Criteria for Clinical and Laboratory VariablesObstructive sleep apnea was defined as an obstructive apnea-hypopnea index (OAHI) ≥ 1.18 Severity of OSA was further classified into 3 levels (regardless of adenotonsillectomy status): no OSA, OAHI < 1; mild OSA, 1 ≤ OAHI < 5; or moderate-severe OSA, OAHI ≥ 5, utilizing the OAHI categories of the composite score for polysomnography severity proposed by Montgomery-Downs et al.19 Body mass index (BMI; kg/m2) was calculated from height and weight measured at the time of polysomnography, and when available checked for accuracy against a height and weight measured during a clinical visit closest to the time of polysomnography. Age groups were defined as 2 to 5 years, 6 to 10 years, 11 to 14 years, and 15 to 18 years of age, dividing the sample approximately equally. For comparisons by adenotonsillectomy status, there were 3 OSA/adenotonsillectomy conditions: No OSA/No AT, OAHI < 1 and no adenotonsillectomy; OSA/No AT, OAHI ≥ 1 and no adenotonsillectomy; and AT, adenotonsillectomy performed for any indication.PolysomnographyEach child underwent overnight polysomnography (Rembrandt version 7.4, Medcare, Reykjavik, Iceland) with ≥ 6 h of recording time, monitored by registered technicians trained in pediatric polysomnography. The following parameters were continuously recorded: sleep stages, using electroencephalography (C3-A2, C4-A1, O1-A2, O2-A1, Fz-A1); heart rate, by electrocardiography; left and right electrooculogram; submental and tibial electromyogram; oronasal airflow, via thermistor; nasal airflow, via pressure transducer; capnography; chest and abdominal wall excursion using respiratory inductance plethysmography; and SpO2 via pulse oximeter. Subjects were audio and video re-corded. Respiratory events, sleep architecture, arousals, and periodic limb movements during sleep (PLM) were scored using standard criteria20–23 by a pediatric pulmonologist board certified in sleep medicine.Polysomnographic parameters were defined as follows. An obstructive apnea was a decrease in nasal airflow of > 90% despite continued respiratory effort for the duration of ≥ 2 missed breaths. An obstructive hypopnea was a decrease in nasal airflow ≥ 50%, despite persistent respiratory effort, lasting for ≥ 2 missed breaths and associated with a drop in SpO2 ≥ 3%, an awakening, or an arousal. A central apnea was the absence of airflow accompanied by an absence of respiratory effort, lasting ≥ 20 sec or at least 2 missed breaths and associated with an arousal, an awakening, or a desaturation ≥ 3%. A mixed apnea included components of both an obstructive and a central apnea. The OAHI was the sum of obstructive apneas, obstructive hypopneas, and mixed apneas per hour of sleep. Sleep stages are presented as the percent of total sleep time spent in each stage. Non-rapid eye movement (NREM) sleep stage 3 was the sum of reported NREM 3 and NREM 4 sleep stages based on scoring criteria in effect during the study period.Sleep efficiency was the ratio of sleep time to time in bed (lights out to lights on). Sleep latency was the number of minutes from lights out to the onset of the first of 3 consecutive epochs of NREM 1 sleep or the first epoch of any other sleep stage. Wake after sleep onset was the number of minutes of wake between sleep onset and sleep offset. An arousal was an abrupt shift in electroencephalographic frequency ≥ 3 sec separated by ≥ 10 sec of stable sleep. An index was calculated as the number of events per hour of sleep. Arousal indices were classified as (1) total arousal index, the sum of all-cause arousals; (2) respiratory arousal index, arousals immediately following an obstructive apnea or hypopnea; (3) PLM arousal index, arousals immediately following PLMs; and (4) spontaneous arousals. Periodic limb movements were defined as a series of ≥ 4 consecutive leg movements having a period length (time between onset of consecutive leg movements) of 5-90 sec and lasting 0.5-5 sec (study period 2004-2006) or 0.5-10 sec (study period 2007-2008). Polysomnograms were not available for rescoring PLMs uniformly across the entire study period, thus potentially underscoring PLMs prior to the change in scoring rules in 2007 and presenting a limitation of these analyses. However, no significant difference in the mean PLM index was found between sleep studies performed during the period 2004-2006 (n = 27) and those performed during 2007-2008 (n = 26; U = 265.5, p = 0.12), suggesting that the mid-study change in scoring of PLMs during sleep did not affect these results. Leg movements occurring within 0.5 sec of an apnea or hypopnea or following an arousal were not scored as PLMs. A positive screen for PLM disorder was defined as a PLM index > 5 per hour of sleep.Statistical AnalysisStatistical analysis was performed using the Statistical Package for the Social Sciences (SPSS, Inc.; Chicago, IL) version 14.0. Alpha was set at 0.05 with Bonferroni correction for multiple post hoc comparisons, and all analyses were two-tailed. Descriptive statistics included mean ± standard deviation, range and percent. Percentages were based on the number of available subjects where data were missing. Data were not normally distributed, so nonparametric statistics were used to test associations and group differences, including Spearman rho, Mann-Whitney (U) test, and Kruskal-Wallis test.RESULTSSample characteristics by genotype are shown in Table 1. Based on polysomnography, 38 of 55 children (69.1%) had OSA, with 24 (43.6%) having mild and 14 (25.5%) having moderate-severe OSA. The OAHI ranged from 0 to 66.6 events per hour of sleep, with a mean OAHI for the no OSA, mild OSA, and moderate-severe OSA groups of 0.4 ± 0.3, 2.6 ± 1.1 and 16.4 ± 16.0, respectively. Mean SpO2 ranged from 82.9% to 99.2% and averaged 95.8 ± 2.5, 96.6 ± 2.5, and 94.8 ± 5.5 for the no, mild, and moderate-severe OSA groups, respectively, with no significant difference between groups. The percent of sleep time spent at SpO2 < 90% (T90) ranged from 0% to 96.6% and increased nonsignificantly across OSA severity groups, averaging 1.9% ± 4.7%, 2.3% ± 10.4%, and 17.0% ± 33.8%, respectively, for the no, mild, and moderate-severe OSA groups. The PLM index ranged from 0 to 56.5 per hour of sleep and averaged 4.7 ± 8.8, with 14 of 53 (26.4%) children in the full sample and 5 of 17 (29.4%) children without OSA screening positive for PLM disorder. The PLM index (n = 46) was highest in the no OSA group, averaging 6.3 ± 13.8, versus 3.6 ± 5.0 and 3.8 ± 5.2 for the mild OSA and moderate-severe OSA groups, respectively, with no significant difference between groups. The PLM arousal index averaged 0.79 ± 1.2 ranging from 0 to 6.6 per hour of sleep, with 15.8% of PLMs associated with arousals.Table 1 Demographic and clinical characteristics of children with sickle cell diseaseHb SS (n = 41)Hb SC (n = 14)N (%)Mean ± SDN (%)Mean ± SDAge (years)419.4 ± 4.6149.9 ± 4.7 Sex, male20 (48.8)4 (28.6)Body mass index (kg/m2) (BMI z-score)4118.9 ± 6.0 (0.11 ± 1.25)1419.2 ± 3.7 (0.58 ± 0.84) Daytime SpO2(%)3997.4 ± 2.01299.3 ± 0.6 Systolic blood pressure (mm Hg)40114.5 ± 11.212113.5 ± 8.6 Diastolic blood pressure (mm Hg)4063.7 ± 7.51267.6 ± 6.6 Hemoglobin (g/dL)398.4 ± 1.3 1310.6 ± 0.8 White blood count (109/L)3912.6 ± 4.0119.3 ± 1.9 Hydroxyurea therapya (yes)14 (34.1)2 (14.3)Chronic transfusion therapya (yes)3 (7.3)0Adenotonsillectomy (yes)6 (14.6)4 (28.6)aAt time of polysomnogram. BMI refers to body mass index; Hb, hemoglobin genotype; SpO2, oxyhemoglobin saturation.The average BMI of the sample was 18.9 ± 5.4 (z-score 0.23 ± 1.2), with an average BMI for the no OSA, mild OSA, and moderate-severe OSA groups of 19.9 ± 5.1 (z-score 0.26 ± 0.9), 19.2 ± 4.8 (z-score 0.52 ± 1.0), and 17.4 ± 6.8 (z-score −0.30 ± 1.6), respectively. The BMI was negatively associated with obstructive indices, including the obstructive apnea index (rho = −0.289, p = 0.03), the obstructive hypopnea index (rho = −0.282, p = 0.04), and the OAHI (rho = −0.301, p = 0.03), suggesting that as obstructive indices increased, BMI decreased. The BMI was also negatively associated with peak end-tidal carbon dioxide (rho = −0.375, p = 0.03).Sleep Parameters by Hemoglobin GenotypeForty-one children had Hb SS, and 14 had Hb SC disease. Fourteen (34.1%) children with Hb SS did not have OSA, while 16 (39.0%) had mild OSA and 11 (26.8%) had moderate-severe OSA. Among those with Hb SC, 3 (21.4%) children had no OSA, while 8 (57.1%) had mild OSA and 3 (21.4%) had moderate-severe OSA. Sleep parameters by genotype are shown in Table 2. Eight children (14.5%) with Hb SS, but none with Hb SC, had an OAHI > 10. Mean SpO2 was significantly lower (U = 139.0, p = 0.004) and T90 was significantly higher (U = 179.5, p = 0.03) in children with Hb SS than in those with Hb SC. Mean SpO2 was 93% or lower in 10 of 41 (24.4%) Hb SS children, indicating nocturnal hypoxemia.21 No child with Hb SC had a mean SpO2 below 95%. The T90 was > 10% for 6 of 41 (14.6%) children with Hb SS, with 3 spending more than half the night below SpO2 90%, and one child having a T90 of 96.6%. Children with Hb SC all had a T90 < 1% (0.01 ± 0.02). Nearly 17% (9 of 54) of the sample experienced oxyhemoglobin desaturation below SpO2 80%, with 2 children, both with Hb SS, having desaturations below 60%. Nadir SpO2 during a respiratory event was 93% or lower in 33 of 40 (82.5%) children with Hb SS, versus 9 of 14 (64.3%) children with Hb SC.Table 2 Polysomnography parameters in children with sickle cell disease, by genotypeParametersHb SSHb SCpa Respiratory parametersnMean ± SDRangenMean ± SDRange OAHI (n/h)416.2 ± 11.70-66.6143.1 ± 2.10.3-7.90.53 OAI (n/h)412.0 ± 5.40-31.5141.3 ± 1.50-4.00.41 OHI (n/h)414.2 ± 6.80-35.1141.8 ± 1.30.3-5.30.75 Mixed apnea index (n/h)410.1 ± 0.20-0.8140.1 ± 0.10-0.30.11 Central apnea index (n/h)410.2 ± 0.40-1.9140.1 ± 0.20-0.50.93 Mean SpO2 (%)4195.2 ± 3.882.9-99.21498.0 ± 0.895.9-99.10.004 Nadir SpO2 (%)4085.6 ± 10.554.3-98.41490.8 ± 5.178.3-98.40.07 T90 (%)418.0 ± 22.00-96.6140.01 ± 0.020-0.10.03 PETCO2 (mm Hg)2751.9 ± 8.236.0-71.0853.1 ± 4.746.0-61.00.44 Sleep architecture, periodic limb movement index, and arousals Total sleep time (min)41430.6 ± 81.2107-54814445.6 ± 53.1335-5480.73 Sleep efficiency (%)4181.5 ± 15.221.4-98.11486.2 ± 8.270.2-97.80.51 Sleep latency (min)4153.9 ± 70.50-392.01426.1 ± 18.50.05-62.50.29 REM latency (min)40121.1 ± 58.249.0-236.014114.6 ± 59.744.5-222.00.55 Wake after sleep onset (min)4146.6 ± 50.62-2451443.8 ± 28.76-1100.46 NREM 1 (%)373.1 ± 3.20.2-14.0143.3 ± 3.00.5-11.90.52 NREM 2 (%)3752.9 ± 9.323.4-68.81453.4 ± 6.842.6-64.30.87 NREM 3 (%)4124.8 ± 7.912.5-48.81423.3 ± 6.011.4-31.20.61 REM (%)4119.4 ± 4.511.4-27.41420.2 ± 4.513.2-26.70.53 PLM index (n/h)393.5 ± 5.40-20.9147.5 ± 14.60-56.50.39 PLM arousal index (n/h)340.77 ± 1.30-6.6120.83 ± 0.98 0-3.30.41 Respiratory arousal index (n/h)412.8 ± 4.60-21.5141.8 ± 1.20.4-4.50.31 Spontaneous arousal index (n/h)416.8 ± 3.51.1-16.8145.2 ± 2.90.4-9.50.16 Total arousal index (n/h)4112.6 ± 6.53.4-28.7149.9 ± 4.33.1-17.90.17 aMann-Whitney test. OAHI, obstructive apnea-hypopnea index; OAI, obstructive apnea index; OHI, obstructive hypopnea index; PETCO2, peak end-tidal carbon dioxide; PLM, periodic limb movements during sleep; SpO2, oxyhemoglobin saturation; T90, percent sleep time below SpO2 90%.There were no significant differences between genotypes on sleep architecture, arousals, or PLM index. Children with Hb SS tended to have shorter sleep times, poorer sleep efficiency, more total arousals, increased sleep onset latency, and more wake after sleep onset than did children with Hb SC. Children screening positive for PLM disorder included 8 of 39 (20.5%) with Hb SS and 6 of 14 (42.9%) with Hb SC, a nonsignificant difference.Sleep Parameters by AgeThe average age of the sample was 9.5 ± 4.6 years. Age was negatively correlated with several respiratory parameters, including the OAHI (rho = −0.364, p = 0.006), obstructive apnea index (rho = −0.370, p = 0.005), and mean SpO2 (rho = −0.282, p = 0.04). Differences in sleep parameters are compared between age groups in Table 3.Table 3 Polysomnographic parameters and BMI in children with sickle cell disease, by age groupParameter2-5 years6-10 years11-14 years15-18 years Respiratory parametersnMean ± SD (Range)nMean ± SD (Range)nMean ± SD (Range)nMean ± SD (Range) OAHI (n/h)156.3 ± 5.5a (0.6 - 19.3)167.6 ± 16.8 (0 - 66.6)142.4 ± 4.6a (0.2 - 18.2)105.0 ± 7.6 (0.3 - 19.5) OAI (n/h)152.1 ± 3.1 (0 - 12.0)162.9 ± 7.8 (0 - 31.5)140.6 ± 1.3 (0 - 4.2)101.4 ± 3.0 (0 - 9.3) OHI (n/h)154.1 ± 4.0a (0.6 - 15.8)164.6 ± 9.1 (0 - 35.1)141.7 ± 3.4a (0.1 - 13.4)103.6 ± 5.0 (0.3 - 15.2) Mixed apnea index (n/h)150.2 ± 0.3 (0 - 0.8) 160.03 ± 0.04 (0 - 0.1)140.1 ± 0.2 (0 - 0.6)100 (0) Central apnea index (n/h)150.2 ± 0.2 (0 - 0.7)160.1 ± 0.3 (0 - 1.0)140.2 ± 0.5 (0 - 1.9)100.2 ± 0.3 (0 - 0.7) Mean SpO2 (%)1596.2 ± 4.3 (84.3 - 99.2)1695.9 ± 3.9 (82.9 - 99.1)1496.2 ± 2.7 (90.6 - 98.6)1095.1 ± 2.7 (89.8 - 98.8) Nadir SpO2 (%)1584.6 ± 11.4 (56.4 - 94.4)1588.8 ± 5.9 (78.3 - 98.4)1490.5 ± 4.7 (82.8 - 98.4)1082.7 ± 14.1 (54.3 - 94.4) T90 (%)159.8 ± 26.6 (0 - 96.6)165.5 ± 21.7 (0 - 89.6)142.2 ± 5.1 (0 - 15.1)106.1 ± 16.0 (0 - 51.3) PETCO2 (mm Hg)951.4 ± 9.6 (36.0 - 70.0)1254.3 ± 8.4 (42.0 - 71.0)953.7 ± 4.0 (48.0 - 59.0)546.0 ± 1.2 (45.0 - 48.0) Sleep architecture, periodic limb movement index, and arousals Total sleep time (min)15437.6 ± 11.2 (326.5 - 528.0)16455.8 ± 47.6 (331.0 - 526.0)14454.8 ± 62.5 (347.0 - 548.0)10367.0 ± 120.0 (107.0 - 548.0) Sleep efficiency (%)1582.9 ± 11.2 (62.1 - 98.1)1686.9 ± 9.0 (64.5 - 96.6)1485.2 ± 10.1 (65.0 - 97.8)1072.0 ± 22.4 (21.4 - 96.4) Sleep latency (min)1544.1 ± 50.0 (0.5 - 141.5)1628.3 ± 20.9 (1.5 - 69.0)1443.2 ± 44.6 (0 - 163.5)1085.7 ± 116.8 (5.0 - 392.0) REM latency (min)1520.0 ± 5.0 (13.2 - 26.9)1619.7 ± 4.1 (14.2 - 27.4)1417.9 ± 4.8 (11.4 - 26.7)1021.1 ± 3.7 (13.1 - 25.3) Wake after sleep onset (min)1549.3 ± 50.0 (2 - 182)1641.7 ± 36.6 (3 - 119)1439.1 ± 25.8 (6 - 94)1057.2 ± 72.2 (4 - 245) NREM 1 (%)152.7 ± 2.9 (0.2 - 10.3)142.3 ± 2.6 (0.2 - 9.6)132.8 ± 1.9 (0.5 - 7.0)95.4 ± 4.5 (1.2 - 14.0) NREM 2 (%)1549.3 ± 9.5 (23.4 - 64.9)1452.3 ± 8.5 (35.9 - 68.7)1357.3 ± 6.8 (47.0 - 68.8)954.2 ± 8.0 (36.4 - 64.3) NREM 3 (%)1527.9 ± 7.4 (19.6 - 48.8)1627.1 ± 6.1a (14.1 - 37.1)1420.9 ± 5.4a (12.5 - 28.9)1019.6 ± 7.9 (11.4 - 36.3) REM (%)1520.0 ± 5.0 (13.2 - 26.9)1619.7 ± 4.1 (14.2 - 27.4)1417.9 ± 4.8 (11.4 - 26.7)1021.1 ± 3.7 (13.1 - 25.3) PLM index (n/h)145.9 ± 6.7 (0 - 20.9)164.8 ± 14.0 (0 - 56.5)134.5 ± 5.0 (0 - 15.1)102.2 ± 3.1 (0 - 8.6) PLM arousal index (n/h)131.2 ± 1.9 (0 - 6.6) 120.4 ± 0.7 (0 - 1.7)121.1 ± 1.0 (0 - 3.3)90.4 ± 0.5 (0 - 1.2) Respiratory arousal index (n/h)153.2 ± 2.2a (0.4 - 7.5)163.3 ± 6.1 (0 - 21.5)141.4 ± 3.0a (0 - 11.6)102.1 ± 3.0 (0 - 8.9) Spontaneous arousal index (n/h)158.2 ± 3.4 (2.6 - 15.4)166.1 ± 4.0 (0.4 - 16.8)145.1 ± 2.3 (1.8 - 8.7)105.8 ± 3.1 (1.1 - 9.5) Total arousal index (n/h)1515.0 ± 5.7a (8.6 - 28.7)1611.0 ± 6.8 (3.1 - 27.1)1410.3 ± 5.2a (4.0 - 24.4)1011.0 ± 6.1 (3.4 - 20.4) Body mass indexnMean ± SD (BMI z - score)nMean ± SD (BMI z - score)nMean ± SD (BMI z - score)nMean ± SD (BMI z - score) BMI (kg/m2)1516.1 ± 1.8 (0.2 ± 1.2)1616.2 ± 1.9 (-0.03 ± 0.8)1421.5 ± 6.1 (0.5 ± 1.4)1024.1 ± 6.8 (0.4 ± 1.3) Post hoc Mann-Whitney test of paired group differences where Kruskal-Wallis test was significant, with Bonferroni correction for number of comparisons,ap ≤ 0.008. Bolded values highlight significant group differences for that variable. BMI, body mass index; OAHI, obstructive apnea-hypopnea index; OAI, obstructive apnea index; OHI, obstructive hypopnea index; PETCO2, peak end-tidal carbon dioxide; PLM, periodic limb movements during sleep; SpO2, oxyhemoglobin saturation; T90, percent sleep time below SpO2 90%.Of the parameters related to sleep architecture, arousals or PLM index, age was positively correlated with NREM 2 (rho = 0.382, p = 0.006) and negatively correlated with NREM 3 (rho = −0.443, p = 0.001), suggesting that as age increased, more sleep time was spent in lighter (NREM 2) sleep and less was spent in slow wave (NREM 3) sleep. Age was also significantly negatively correlated with total arousals (rho = −0.272, p = 0.04) and respiratory arousals (rho = −0.349, p = 0.009) and approached a negative association with spontaneous arousals (rho = −0.252, p = 0.06), suggesting that arousal indices improved with age. However, age group differences in arousals reflected differences in obstructive indices, in that fewer obstructive events were seen in age groups having fewer total and respiratory arousals. While nonsignificant, the oldest age group had shorter total sleep time, lower sleep efficiency, longer sleep latency, and more wake after sleep onset than the other age groups. There was no significant difference in the PLM index or PLM arousal index between age groups.Sleep Parameters by Adenotonsillectomy StatusThirty-two OSA-positive children had not undergone adenotonsillectomy at the time of polysomnography. Eight children had adenotonsillectomy prior to polysomnography, and 2 underwent polysomnography both before and after adenotonsillectomy. Indications for adenotonsillectomy were largely unreported in this sample but included 2 children with adenotonsillar hypertrophy and 2 children with documented OSA. Two of these 4 children had an additional indication of recurrent otitis media. Sleep parameters by OSA/adenotonsillectomy condition are shown in Table 4. Descriptive statistics in this table include both pre- and post-adenotonsillectomy polysomnography data for the 2 children with available data; thus statistical comparisons would violate the assumption of independent groups and are not made. Lag time between adenotonsillectomy and follow-up polysomnography averaged 63.4 ± 49.5 months, with a range of 3 to 143 months.Table 4 Polysomnography parameters, age, and BMI in children with sickle cell disease, by adenotonsillectomy statusParametersNo OSA, no adenotonsillectomyOSA, no adenotonsillectomyAdenotonsillectomynMean ± SDRangenMean ± SDRangenMean ± SDRange Age (years)1511.7 ± 3.92.5-17.6327.8 ± 4.52.4-17.61010.6 ± 4.63.0-17.1 Respiratory parameters OAHI (n/h)150.4 ± 0.30-0.9328.9 ± 12.51.0-66.6104.4 ± 5.50.4-16.9 OAI (n/h)150.1 ± 0.10-0.5323.0 ± 5.90-31.5100.8 ± 1.10-2.9 OHI (n/h)150.4 ± 0.30-0.9325.8 ± 7.10.3-35.1103.5 ± 4.80.3-14.2 Mixed apnea index (n/h)150.01 ± 0.030-0.1320.1 ± 0.20-0.8100.1 ± 0.10-0.4 Central apnea index (n/h)150.2 ± 0.30-1.0320.1 ± 0.20-0.7100.3 ± 0.60-1.9 Mean SpO2 (%)1595.5 ± 2.590.6-99.13295.7 ± 4.182.9-99.21096.9 ± 2.592.3-98.9 Nadir SpO2 (%)1589.9 ± 3.482.8-94.43184.1 ± 11.654.3-98.41088.0 ± 11.457.6-95.0 T90 (%)152.1 ± 5.00-15.4329.2 ± 24.90-96.6101.6 ± 4.20-13.4 PETCO2 (mm Hg)948.9 ± 4.045.0-58.02252.8 ± 8.836.0-71.0653.3 ± 4.646.0-58.0 Sleep architecture, periodic limb movement index, and arousals Total sleep time (min)15447.3 ± 113.6107-54832431.3 ± 58.8244-52810431.9 ± 59.6335-520 Sleep efficiency (%)1581.3 ± 19.921.4-96.63282.3 ± 14.521.4-98.11085.5 ± 8.970.2-96.0 Sleep latency (min)1567.2 ± 99.94.5-392.03242.2 ± 43.40.5-151.01024.8 ± 19.60-55.5 REM latency (min)1592.6 ± 42.049.0-170.032120.6 ± 59.644.5-236.010150.5 ± 56.946.0-224.0 Wake after sleep onset (min)1534.2 ± 43.04-1823251.0 ± 49.52-2451048.3 ± 33.43-110 NREM 1 (%)123.1 ± 3.80.5-14.0312.9 ± 2.60.2-10.3104.7 ± 3.60.2-11.9 NREM 2 (%)1255.4 ± 8.736.4-67.43151.3 ± 8.723.4-68.71053.5 ± 9.137.1-68.8 NREM 3 (%)1521.5 ± 7.311.4-36.43226.5 ± 7.014.2-48.81022.0 ± 6.912.1-31.1 REM (%)1519.9 ± 4.512.3-27.43219.8 ± 4.412.7-26.91019.8 ± 5.411.4-27.3 PLM index (n/h)156.8 ± 14.70-56.5313.3 ± 5.10-20.994.6 ± 3.50-9.5 PLM arousal index (n/h)140.6 ± 0.80-2.0280.8 ± 1.40-6.651.3 ± 1.40-3.3 Respiratory arousal index (n/h)150.3 ± 0.30-1.1324.0 ± 4.80-21.5101.7 ± 1.30-4.5 Spontaneous arousal index (n/h)154.8 ± 2.80.4-9.2327.1 ± 3.70.9-16.8106.2 ± 2.21.8-9.5 Total arousal index (n/h)157.5 ± 2.73.1-11.03214.1 ± 8.64.2-28.71011.5 ± 4.15.7-17.9 Body mass indexnMean ± SDz-scorenMean ± SDz-scorenMean ± SDz-score BMI (kg/m2)1519.2 ± 4.40.1 ± 0.8 3217.7 ± 5.10.04 ± 1.31022.3 ± 6.31.2 ± 0.9 Data includes pre- and post-adenotonsillectomy data on 2 subjects.BMI, body mass index; OAHI, obstructive apnea-hypopnea index; OAI, obstructive apnea index; OHI, obstructive hypopnea index; OSA, obstructive sleep apnea; PETCO2, peak end-tidal carbon dioxide; PLM, periodic limb movements during sleep; SpO2, oxyhemoglobin saturation; T90, % sleep time below SpO2 90%.Respiratory indices were generally better in the AT than the OSA/No AT condition, but were often not normal. The largest mean differences between the OSA/No AT and the AT conditions were for the OAHI and the T90. The mean PLM index was higher in children who had adenotonsillectomy than untreated OSA-positive children. Post-adenotonsillectomy, 5 of 9 (56%) children screened positive for PLM disorder, compared with 6 of 31 (19%) in the OSA/No AT condition and 4 of 15 (26%) in the No OSA/No AT condition. The AT condition demonstrated the highest BMI; however, those children were, on average, 2 years older than those in the OSA/No AT condition, which was the youngest group. Pre-adenotonsillectomy polysomnography and BMI were not available for 8 children who had adenotonsillectomy, so change from pre- to post- adenotonsillectomy could not be analyzed.The 2 children with both pre- and p
Referência(s)