Obstructive sleep apnea syndrome in siblings: an 8-year Swedish follow-up study

Preterm birth and risk of sleep-disordered breathing from childhood into mid-adulthood

BACKGROUND

Preterm birth (gestational age <37 weeks) has previously been associated with cardiometabolic and neuropsychiatric disorders into adulthood, but has seldom been examined in relation to sleep disorders. We conducted the first population-based study of preterm birth in relation to sleep-disordered breathing (SDB) from childhood into mid-adulthood.

METHODS

A national cohort study was conducted of all 4 186 615 singleton live births in Sweden during 1973-2014, who were followed for SDB ascertained from nationwide inpatient and outpatient diagnoses through 2015 (maximum age 43 years). Cox regression was used to examine gestational age at birth in relation to SDB while adjusting for other perinatal and maternal factors, and co-sibling analyses assessed for potential confounding by unmeasured shared familial factors.

RESULTS

There were 171 100 (4.1%) persons diagnosed with SDB in 86.0 million person-years of follow-up. Preterm birth was associated with increased risk of SDB from childhood into mid-adulthood, relative to full-term birth (39-41 weeks) [adjusted hazard ratio (aHR), ages 0-43 years: 1.43; 95% confidence interval (CI), 1.40, 1.46; P <0.001; ages 30-43 years: 1.40; 95% CI, 1.34, 1.47; P <0.001]. Persons born extremely preterm (<28 weeks) had more than 2-fold risks (aHR, ages 0-43 years: 2.63; 95% CI, 2.41, 2.87; P <0.001; ages 30-43 years: 2.22; 95% CI, 1.64, 3.01; P <0.001). These associations affected both males and females, but accounted for more SDB cases among males (additive interaction, P = 0.003). Co-sibling analyses suggested that these findings were only partly due to shared genetic or environmental factors in families.

CONCLUSIONS

Preterm-born children and adults need long-term follow-up for anticipatory screening and potential treatment of SDB.

Familial Aggregation and Heritability of Obstructive Sleep Apnea Using Children Probands

STUDY OBJECTIVES

Previous studies suggest the presence of familial aggregation of obstructive sleep apnea (OSA) in adults. However, similar data on childhood OSA are limited. This family study aimed to investigate the heritability and familial aggregation of childhood OSA and to examine whether significant differences existed between patients of normal weight and overweight.

METHODS

Children aged 6 to 18 years were recruited as probands either from attendants to sleep clinic (with habitual snoring) or the community (without habitual snoring). Parents and siblings of the probands were also invited to participate. All participants underwent nocturnal sleep study.

RESULTS

A total of 229 probands took part, of whom 33 had moderate to severe OSA, 70 had mild disease, and 126 had no OSA. A total of 412 relatives were also recruited. Although the overall heritability of obstructive apnea-hypopnea index (OAHI) was not significant (h² ± SE = 0.03 ± 0.09, P = .37), it was significant in overweight individuals on subgroup analysis (h² ± SE = 0.43 ± 0.24, P = .032). Significant interaction effect of overweight was demonstrated in both heritability and familial aggregation analyses. Bivariate genetic analysis found that the genetic correlation between OAHI and body mass index in overweight individuals (ρg ± SE = 0.63 ± 0.18) was significantly different from both 0 (P = .005) and 1 (P = .025).

CONCLUSIONS

The differential results of heritability and familial aggregation of OSA in normal weight and overweight subgroups substantiated the recommendation of separating childhood OSA into normal weight and overweight subtypes. In the overweight subgroup, there may be obesity-independent components involved in the genetic variance of OAHI, although a significant proportion of the genetic variance is shared with obesity.

Prenatal, Perinatal, and Early Childhood Factors Associated with Childhood Obstructive Sleep Apnea

OBJECTIVES

To investigate prenatal, perinatal, and early childhood factors, including cord and early childhood plasma leptin, on a clinical diagnosis of obstructive sleep apnea (OSA) among children in the Boston Birth Cohort.

STUDY DESIGN

We conducted a secondary analysis of 2867 mother-child pairs from the Boston Birth Cohort who were enrolled between 1998 and 2014 at Boston Medical Center and followed from birth to age 16 years. Child's OSA was defined based on clinical diagnoses documented in the medical record. Plasma leptin was measured in cord and early childhood blood samples. Logistic regression was used to examine individual and combined effects of early life factors on the risk of OSA, adjusting for potential confounders.

RESULTS

The mean age of the study children was 6.39 years (SD = 3.77); 49.3% were girls, and 209 (7.3%) had ever been diagnosed with OSA. Four significant risk factors for OSA were identified: maternal obesity/diabetes during pregnancy (OR, 1.63; 95% CI, 1.21-2.21; P = .001), preterm/low birth weight (OR, 1.74; 95% CI, 1.30-2.32; P < .001), early childhood obesity (OR, 1.89; 95% CI, 1.37-2.62; P < .001), and high leptin levels in early childhood (OR, 1.94; 95% CI, 1.22-3.09; P = .005). The presence of all these 4 risk factors significantly amplified the odds of OSA by about 10 times (OR, 9.95; 95% CI, 3.42-28.93; P < .001) compared with those lacking these factors.

CONCLUSIONS

Our findings, if further confirmed, provide new insight into the early life risk factors of pediatric OSA and underscore the need for early screening and prevention of OSA among children with those risk factors.

Pediatric Sleep Apnea Syndrome: An Update

Obstructive sleep apnea syndrome (OSAS) may be central neurologic (<5%) or obstructive (>95%) in origin and is a relatively prevalent condition in children. It affects 1%-5% of children aged 2-8 years and is caused by a variety of different pathophysiologic abnormalities. Cardiovascular, metabolic, and neurocognitive comorbidities can occur in both children and adults when left untreated. It also can cause severe behavioral problems in children. The American Academy of Pediatrics recommends that all children be screened with an appropriate history and physical examination for symptoms and signs suggestive of OSAS. The diagnosis is primarily made clinically and confirmed by polysomnographic findings. Treatment depends on the child's age, underlying medical problems, polysomnography findings, and whether or not there is upper airway obstruction usually secondary to enlarged adenoids and/or tonsils, allergic and nonallergic rhinitis, acute and chronic sinusitis, and other upper airway pathology. If enlarged adenoid or tonsils or both conditions exist, an adenoidectomy, tonsillectomy, or adenotonsillectomy remains the treatment of choice. Pharmacotherapy of OSAS has shown some effect in children with mild symptoms. This paper reviews the prevalence, pathophysiology, clinical presentation, diagnosis, and treatment of OSAS.

Treatment of obstructive sleep apnea in children

Obstructive sleep apnea (OSA) in children is a frequent disease for which optimal diagnostic methods are still being defined. Treatment of OSA in children should include providing space, improving craniofacial growth, resolving all symptoms, and preventing the development of the disease in the adult years. Adenotonsillectomy (T&A) has been the treatment of choice and thought to solve young patient's OSA problem, which is not the case for most adults. Recent reports showed success rates that vary from 27.2% to 82.9%. Children snoring regularly generally have a narrow maxilla compared to children who do not snore. The impairment of nasal breathing with increased nasal resistance has a well-documented negative impact on early childhood maxilla-mandibular development, making the upper airway smaller and might lead to adult OSA. Surgery in young children should be performed as early as possible to prevent the resulting morphologic changes and neurobehavioral, cardiovascular, endocrine, and metabolic complications. Close postoperative follow-up to monitor for residual disease is equally important. As the proportion of obese children has been increasing recently, parents should be informed about the weight gain after T&A. Multidisciplinary evaluation of the anatomic abnormalities in children with OSA leads to better overall treatment outcome.

Heritability of abnormalities in cardiopulmonary coupling in sleep apnea: use of an electrocardiogram-based technique

RATIONALE

Studies of the genetics of obstructive sleep apnea may be facilitated by identifying intermediate traits with high heritability that quantify etiological pathways, such as those related to respiratory control. Electrocardiogram (ECG)-based sleep spectrograms, measuring the coupling between respiratory modulation of ECG QRS-wave amplitude and heart rate variability, may provide measures of sleep state and ventilatory dynamics during sleep. We evaluated the familial aggregation of distinctive spectrographic biomarkers of unstable sleep, related to elevated-low frequency cardiopulmonary coupling (e-LFC), to assess their utility in genetic studies.

METHODS

622 participants from 137 families from the Cleveland Family Study underwent standardized polysomnography (PSG). From the ECG signal on the PSG, the interbeat interval time series and the corresponding ECG-derived respiratory signal were extracted, and the low frequency (0.01-0.1 Hz) component of their coupling was computed using a fully automated method. Narrow sense heritability of e-LFC was calculated using variance component methods.

RESULTS

A spectral marker of abnormal low frequency cardiopulmonary coupling (e-LFC) demonstrated moderate correlation with apnea hypopnea index (AHI; r = 0.35, P < 0.0001). The heritability estimate for e-LFC, after adjusting for age and sex was 0.32 (P < 10-5) and remained unchanged after additionally adjusting for body mass index or AHI. In biological relatives of those with sleep apnea, a related marker of e-LFC was more prevalent than in controls (P = 0.05).

CONCLUSIONS

Approximately 30% of the variability of e-LFC, measured from a continuous ECG during sleep, is explained by familial factors other than BMI. ECG-based spectrographic measures of cardiopulmonary coupling may provide novel phenotypes for characterizing subgroups of individuals with different propensities and genetic etiologies for sleep apnea or for other conditions associated with sleep fragmentation.

Sibling risk of pediatric obstructive sleep apnea syndrome and adenotonsillar hypertrophy

OBJECTIVES

To estimate sibling risk of hospitalization for children with sleep disordered breathing (SDB), diagnosed with (1) obstructive sleep apnea syndrome (OSAS), or (2) adenotonsillar hypertrophy in the total Swedish population.

DESIGN, SETTING, AND PARTICIPANTS

Using the MigMed database at the Karolinska Institute, we divided the population of Sweden aged 0-18 years into sibling groups based on a shared mother and father and presence of a primary hospital diagnosis of OSAS or adenotonsillar hypertrophy for each individual born between 1978 and 1986, during the follow-up period 1997-2004. Individuals with at least one affected sibling were identified and the incidence rates were computed, using standardized incidence ratios (SIRs) with 95% confidence intervals (CIs). Reference groups were boys and girls with unaffected siblings of 2 or more.

RESULTS

After accounting for socioeconomic status, age, and geographic region, boys with at least one sibling with OSAS had an increased risk of having OSAS (SIR, 33.2; 95% CI, 16.5-64.8), and in girls the SIR was 40.5 (19.4-81.4). For hypertrophy of the tonsils or hypertrophy of the adenoids and tonsils the corresponding SIRs were 4.53 (3.0-6.8) for boys and 4.94 (3.3-7.4) for girls.

CONCLUSIONS

The study indicate an increased sibling risk of sleep disordered breathing in children, which may be due to heritable genes and/or shared environment such as increased awareness among family members or referring doctors. Caregivers should ask parents if siblings have similar symptoms, and thus offer them early treatment.