Genetic influences on the onset of obstructive sleep apnoea and daytime sleepiness: a twin study

Advances in non-coding RNA as a biomarker for obstructive sleep apnoea hypoventilation syndrome

PURPOSE

Obstructive sleep apnoea hypoventilation syndrome (OSAHS) is a common sleep disorder that affects multiple body systems, which in turn is closely associated with cognitive dysfunction, diabetes mellitus, oncological cardiovascular diseases and metabolic disorders. In recent years, non-coding RNA (ncRNA) has emerged as a new opportunity for biomarker discovery. We therefore discuss the research progress and potential role of ncRNAs in obstructive sleep apnea hypoventilation syndrome.

METHODS

This review systematically searched relevant academic literature from PubMed, Web of Science and other databases. During the retrieval process, a combination of keywords such as "OSAHS", "ncRNA", "lncRNA", "miRAN", "circRNA" was used for search.

RESULTS

Circulating ncRNA has good area under the ROC curve, sensitivity and specificity in the diagnosis of OSAHS, and has the potential to become a diagnostic marker for OSAHS, while several circulating ncRNAs or circulating ncRNAs in combination with other tests such as the Obstructive Sleep Apnoea Screening Scale have a higher value of application as a test for OSAHS. Further analyses revealed that many circulating ncRNAs were significantly differentially expressed in the serum of OSAHS patients with different very severities, a potential marker for predicting the severity of OSAHS, and that the ncRNA content of patients' serum also had a significant effect during CPAP therapy, suggesting that it may have potential for therapeutic monitoring. Meanwhile, serum ncRNAs from patients have been shown to be effective in the diagnosis of OSAHS complications such as hypertension, Alzheimer's disease, acute myocardial infarction and atherosclerosis. The expression of up- or down-regulated ncRNAs can regulate different signalling pathways, which in turn affects various OSAHS complications such as pulmonary hypertension, diabetes mellitus, and cognitive dysfunction, and is expected to become a new direction for the treatment of these complications.

CONCLUSIONS

The changes in ncRNA expression in OSAHS patients are expected to be a novel biomarker for the diagnosis and treatment of OSAHS, and can also be used as a potential biomarker for the combination of diabetes mellitus, cardiovascular disease, respiratory disease, and cognitive dysfunction in OSAHS. It is believed that the continuous progress of ncRNA-related research is expected to promote the early detection, diagnosis and treatment of OSAHS and its complications.

Advances in Sleep-Disordered Breathing in Children

Pediatric sleep-disordered breathing disorders are a group of common conditions, from habitual snoring to obstructive sleep apnea (OSA) syndrome, affecting a significant proportion of children. The present article summarizes the current knowledge on diagnosis and treatment of pediatric OSA focusing on therapeutic and surgical advancements in the field in recent years. Advancements in OSA such as biomarkers, improving continuous pressure therapy adherence, novel pharmacotherapies, and advanced surgeries are discussed.

Risk Factors of Obstructive Sleep Apnea (OSA) in Pediatric Patients: A Systematic Review and Meta-analysis

INTRODUCTION

This review aimed to assess the risk factors of Obstructive Sleep Apnea (OSA) in pediatric children, a common condition with serious long-term sequela.

METHODS

PubMed, CENTRAL, Scopus, and Google Scholar were searched using the keywords "Apnea", "Obstructive Sleep" OR "Obstructive Sleep Apnea Syndrome" AND "Child" OR "Children" OR "Pediatrics". Data from 35 studies involving 497,688 pediatric patients diagnosed with OSA using polysomnography were reviewed. Risk factors examined included sex, obesity, neck circumference, tonsillar/adenoid hypertrophy, respiratory infections, nasal stenosis, parental OSA/smoking, ethnicity, preterm birth, and breastfeeding history. Relative Risk (RR) with 95% Confidence Intervals (95% CI) were calculated, using Cochrane Q and I² statistics to estimate heterogeneity.

RESULTS

Tonsillar hypertrophy (RR = 3.55), adenoid hypertrophy (RR = 1.63), respiratory tract infection (RR = 2.59), obesity (RR = 1.74), and family history of OSA (RR = 3.03) were significantly associated with pediatric OSA. White ethnicity was protective (RR = 0.77).

DISCUSSION

Recognizing these risk factors aids in early diagnosis and treatment of pediatric OSA.

Posttraumatic Stress Disorder and Obstructive Sleep Apnea in Twins

Importance

Obstructive sleep apnea (OSA) is a common condition in older adult (aged >65 years) populations, but more mechanistic research is needed to individualize treatments. Previous evidence has suggested an association between OSA and posttraumatic stress disorder (PTSD) but is limited by possible selection bias. High-quality research on this association with a careful evaluation of possible confounders may yield important mechanistic insight into both conditions and improve treatment efforts.

Objective

To investigate the association of current PTSD symptoms and PTSD diagnosis with OSA.

Design, Setting, and Participants

This cross-sectional study of twin pairs discordant for PTSD, which allows for adjustment for familial factors, was conducted using in-laboratory polysomnography from March 20, 2017, to June 3, 2019. The study sample comprised male veteran twins recruited from the Vietnam Era Twin Registry. The data analysis was performed between June 11, 2022, and January 30, 2023.

Exposure

Symptoms of PTSD in twins who served in the Vietnam War. Diagnosis of PTSD was a secondary exposure.

Main Outcomes and Measures

Obstructive sleep apnea was assessed using the apnea-hypopnea index (AHI) (≥4% oxygen saturation criterion as measured by events per hour) with overnight polysomnography. Symptoms of PTSD were assessed using the PTSD Checklist (PCL) and structured clinical interview for PTSD diagnosis.

Results

A total of 181 male twins (mean [SD] age, 68.4 [2.0] years) including 66 pairs discordant for PTSD symptoms and 15 pairs discordant for a current PTSD diagnosis were evaluated. In models examining the PCL and OSA within pairs and adjusted for body mass index (BMI) and other sociodemographic, cardiovascular, and psychiatric risk factors (including depression), each 15-point increase in PCL was associated with a 4.6 (95% CI, 0.1-9.1) events-per-hour higher AHI. Current PTSD diagnosis was associated with an adjusted 10.5 (95% CI, 5.7-15.3) events-per-hour higher AHI per sleep-hour. Comparable standardized estimates of the association of PTSD symptoms and BMI with AHI per SD increase (1.9 events per hour; 95% CI, 0.5-3.3 events per hour) were found.

Conclusions and Relevance

This cross-sectional study found an association between PTSD and sleep-disordered breathing. The findings have important public health implications and may also enhance understanding of the many factors that potentially affect OSA pathophysiology.

Real-world impact of continuous positive airway pressure on sleepiness in patients with obstructive sleep apnea in a national registry

OBJECTIVE

Excessive daytime sleepiness (EDS) persists in some patients with obstructive sleep apnea (OSA) despite continuous positive airway pressure (CPAP) treatment. This study characterized response to CPAP and factors associated with residual EDS.

METHODS

Danish National Patient Registry data were analyzed. Patients with OSA diagnosis (1994-2016), Epworth Sleepiness Scale (ESS) scores and apnea-hypopnea index recorded before beginning CPAP (baseline) and after 1-13 months of CPAP use, and CPAP adherence were included. Odds ratios (OR) for residual EDS after CPAP treatment were estimated using multivariate logistic regression.

RESULTS

Of 1174 patients (mean age, 57 years; 75.5% male), 41.1% had baseline EDS (mild, 13.2%; moderate, 14.0%; severe, 13.9%); 58.9% did not. After CPAP treatment, follow-up mean ESS scores were normal (≤10) for all baseline EDS subgroups; however, 15.6% (n = 183) of patients had residual EDS (mild, 6.7%; moderate, 5.5%; severe, 3.4%). Odds of residual EDS were higher for patients with mild (OR, 5.2; 95% confidence interval [CI], 3.2-8.6), moderate (OR, 4.5; 95% CI, 2.7-7.4), and severe (OR, 13.0; 95% CI, 8.0-21.2) EDS at baseline compared with those with normal daytime sleepiness at baseline. Patients adherent with CPAP use were 38.2% less likely to have residual EDS compared with nonadherent patients (OR, 0.62; 95% CI, 0.43-0.88).

CONCLUSIONS

EDS was common in this cohort of Danish patients with OSA. Baseline EDS severity predicted higher odds of residual EDS. After CPAP treatment, adherence was associated with reduced odds of residual EDS, but EDS persisted in a subgroup of patients.

A Systematic Review of Risk factors for Sleep Apnea

Background

Sleep apnea, a prevalent global health issue, is characterized by repeated interruptions in breathing during sleep. This systematic review aggregates global data to outline a comprehensive analysis of its associated risk factors.

Purpose

The systematic review underscores the global prevalence of sleep apnea and the universal importance of its early detection and management by delineating key risk factors contributing to its development.

Material and Methods

We conducted a thorough systematic review of international medical databases up to July 31, 2023, including PubMed, Medline, and Cochrane Library, to ensure a wide-ranging collection of data reflective of various populations.

Results

The systematic review identifies several risk factors such as obesity, age, gender, neck circumference, family history, smoking, alcohol use, underlying medical conditions, and nasal congestion, highlighting their prevalence across diverse demographics globally.

Conclusion

Emphasizing lifestyle modifications and proactive interventions, our findings advocate for global health strategies to mitigate the risk of sleep apnea and enhance sleep health worldwide.

Association of tumor necrosis factor-α-308G/A polymorphism with the risk of obstructive sleep apnea: A meta-analysis of 14 case-control studies

Although numerous studies have suggested the association between TNF-α-308G/A polymorphism and susceptibility to obstructive sleep apnea (OSA), the results remained controversial and ambiguous. We performed the present meta-analysis to derive a more precise estimation.The PubMed, Embase, Cochrane library, Web of Science, China National Knowledge Infrastructure, Wanfang databases, and Weipu databases (until January 8, 2022) were accessed to retrieve relevant articles. Pooled odds ratios (ORs) with 95% confidence interval (95% CI) were calculated using the STATA statistical software.Totally, fourteen studies involving 2595 cases and 2579 controls were enrolled in this meta-analysis. Pooled results demonstrated significant association between TNF-α-308G/A polymorphism and OSA risk for the overall population(allele model:OR = 1.87 [1.47, 2.38] (n = 14), dominant model: OR = 1.88[1.48, 2.39] (n = 14), recessive model:OR = 2.83 [2.00, 4.00] (n = 11), homozygous model:OR = 3.30 [2.32, 4.68] (n = 11), and heterozygous model:OR = 1.67 [1.36, 2.06] (n = 14); P<0.001, respectively).Subgroup analysis showed that in both Caucasians and Asians, the A allele conferred increased risk to OSA compared to the G allele (Caucasians: OR = 1.40[1.03, 1.90] (n = 5), P = 0.033, Asians: OR = 2.30 [1.62, 3.26] (n = 9), P< 0.001). In subgroup analysis restricted to hospital-based individuals, significant association between TNF-α-308G/A polymorphism and OSA risk was identified under each genetic model. Whereas, in population-based individuals, increased risk of OSA were only found in homozygous model (OR = 2.19[1.23, 3.90] (n = 3), P = 0.008) and recessive model (OR = 1.77 [1.00, 3.13] (n = 3), P = 0.048). There was a substantial between-study heterogeneity (I2 = 69.10%) across studies which was explained by source of control participants (P = 0.036) by meta-regression. The results of leave-one-out meta-analysis and publication bias suggested the reliability and stability of our results.This meta-analysis suggested that TNF-α-308A allele may be a risk factor for the development of OSA. However, large scale,multi-center and well-designed case-control studies are needed in the future.

Heritability of cephalometric variables of airway morphology in twins with completed active growth

BACKGROUND

The interplay between genetic and environmental impacts on dental and facial morphology has been widely analyzed, but little is known about their relative contributions to airway morphology. The aim of this study was to evaluate the genetic and environmental influences on the cephalometric variables of airway morphology in a group of postpubertal twins with completed craniofacial growth.

MATERIALS AND METHODS

The materials comprised lateral head cephalograms of 94 pairs of twins (50 monozygotic, 44 dizygotic) with completed craniofacial growth. Zygosity was determined using 15 specific DNA markers. The computerized cephalometric analysis included 22 craniofacial, hyoideal, pharyngeal structural linear and angular variables. Genetic analysis and heritability estimation were performed using maximum likelihood genetic structural equation modeling (GSEM). Principal component analysis (PCA) was used to assess the correlations between cephalometric measurement variables.

RESULTS

Upper airway dimensions showed moderate to high genetic determination (SPPW-SPP and U-MPW: a2 = 0.64 and 0.5, respectively). Lower airway parameters showed only common and specific environmental determination (PPW-TPP a2 = 0.24, e2 = 0.38; LPW-V c2 = 0.2, e2 = 0.63; PCV-AH c2 = 0.47, e2 = 0.28). The relationship between the maxilla and the hyoid bone (for variables PNS-AH, ANS-AH d2 = 0.9, 0.92, respectively) showed very strong additive genetic determination. The size of the soft palate was affected by additive and dominant genes. Its length (SPL) was strongly influenced by dominant genes, while its width (SPW) showed a moderate additive genetic influence. Owing to correlations in the behavior of variables, the data could be expressed in 5 principal components that jointly explained 36.8% of the total variance.

CONCLUSIONS

The dimensions of the upper airway are strongly determined by genes, while the parameters of the lower airway depend mainly on environmental factors.

TRIAL REGISTRATION

The protocol has been approved by the Kaunas Regional Ethical Committee (No. BE - 2-41., May 13, 2020).

Discovery of genomic loci associated with sleep apnea risk through multi-trait GWAS analysis with snoring

STUDY OBJECTIVES

Despite its association with severe health conditions, the etiology of sleep apnea (SA) remains understudied. This study sought to identify genetic variants robustly associated with SA risk.

METHODS

We performed a genome-wide association study (GWAS) meta-analysis of SA across five cohorts (NTotal = 523 366), followed by a multi-trait analysis of GWAS (multi-trait analysis of genome-wide association summary statistics [MTAG]) to boost power, leveraging the high genetic correlation between SA and snoring. We then adjusted our results for the genetic effects of body mass index (BMI) using multi-trait-based conditional and joint analysis (mtCOJO) and sought replication of lead hits in a large cohort of participants from 23andMe, Inc (NTotal = 1 477 352; Ncases = 175 522). We also explored genetic correlations with other complex traits and performed a phenome-wide screen for causally associated phenotypes using the latent causal variable method.

RESULTS

Our SA meta-analysis identified five independent variants with evidence of association beyond genome-wide significance. After adjustment for BMI, only one genome-wide significant variant was identified. MTAG analyses uncovered 49 significant independent loci associated with SA risk. Twenty-nine variants were replicated in the 23andMe GWAS adjusting for BMI. We observed genetic correlations with several complex traits, including multisite chronic pain, diabetes, eye disorders, high blood pressure, osteoarthritis, chronic obstructive pulmonary disease, and BMI-associated conditions.

CONCLUSION

Our study uncovered multiple genetic loci associated with SA risk, thus increasing our understanding of the etiology of this condition and its relationship with other complex traits.

Behaviour genetics and sleep: A narrative review of the last decade of quantitative and molecular genetic research in humans

During the last decade quantitative and molecular genetic research on sleep has increased considerably. New behavioural genetics techniques have marked a new era for sleep research. This paper provides a summary of the most important findings from the last ten years, on the genetic and environmental influences on sleep and sleep disorders and their associations with health-related variables (including anxiety and depression) in humans. In this review we present a brief summary of the main methods in behaviour genetic research (such as twin and genome-wide association studies). We then discuss key research findings on: genetic and environmental influences on normal sleep and sleep disorders, as well as on the association between sleep and health variables (highlighting a substantial role for genes in individual differences in sleep and their associations with other variables). We end by discussing future lines of enquiry and drawing conclusions, including those focused on problems and misconceptions associated with research of this type. In this last decade our knowledge about genetic and environmental influences on sleep and its disorders has expanded. Both, twin and genome-wide association studies show that sleep and sleep disorders are substantially influenced by genetic factors and for the very first time multiple specific genetic variants have been associated with sleep traits and disorders.

Neurotrophins in the Neuropathophysiology, Course, and Complications of Obstructive Sleep Apnea-A Narrative Review

Obstructive sleep apnea (OSA) is a disorder characterized by chronic intermittent hypoxia and sleep fragmentation due to recurring airway collapse during sleep. It is highly prevalent in modern societies, and due to its pleiotropic influence on the organism and numerous sequelae, it burdens patients and physicians. Neurotrophins (NTs), proteins that modulate the functioning and development of the central nervous system, such as brain-derived neurotrophic factor (BDNF), have been associated with OSA, primarily due to their probable involvement in offsetting the decline in cognitive functions which accompanies OSA. However, NTs influence multiple aspects of biological functioning, such as immunity. Thus, extensive evaluation of their role in OSA might enlighten the mechanism behind some of its elusive features, such as the increased risk of developing an immune-mediated disease or the association of OSA with cardiovascular diseases. In this review, we examine the interactions between NTs and OSA and discuss their contribution to OSA pathophysiology, complications, as well as comorbidities.

Hyoid bone position as an indicator of severe obstructive sleep apnea

BACKGROUND

The objective of this study was to evaluate the relationship between hyoid bone position and severity of obstructive sleep apnea (OSA), and to investigate its value as a complementary diagnostic method.

METHODS

A total of 133 patients who were diagnosed as OSA with an apnea-hypopnea index ≥ 5 were included. Clinical examination, level I polysomnography (PSG) and lateral cephalographic analysis were done. Comprehensive PSG characteristics were compared according to hyoid bone position and the predictive power of the distance between the mandible and hyoid was assessed.

RESULTS

The distance between the hyoid bone and mandibular plane was significantly longer in the severe OSA group (p = 0.013). The distance from hyoid bone to third vertebrae (C3) and hyoid bone to mentum were also longer in the severe OSA group but the difference did not reach statistical significance. The distance between hyoid bone and mandibular plane was effective in predicting severe OSA, with a cut-off value of 19.45 mm (AUC = 0.623, p = 0.040). When grouped according to a distance cut-off value of 19.45 mm, those with a longer distance between the hyoid bone and mandibular plane showed more respiratory disturbance, lower oxygen saturation levels, less deep slow wave sleep, and more fragmented sleep with arousals.

CONCLUSIONS

The distance between the hyoid bone and mandibular plane derived from cephalometric analysis can be a valuable diagnostic parameter that can be easily applied in differentiating severe OSA patients.

The Heritability of Upper Airway Dimensions Using MRI Scans in Twins

Introduction: Obstructive sleep apnea (OSA) is a common disorder characterized by the repetitive collapse of the upper airways during sleep, most likely in the oropharyngeal region. Anatomical factors significantly contribute to the disease development; however, the heritability of the upper airway dimensions, which lead to the collapsibility of the upper airways, is less known. In the current study, we aimed to quantify the impact of heritable and environmental factors on the upper airway dimensions in twins using magnetic resonance imaging (MRI). Methods: We completed head and neck MRI imaging on 110 (66 monozygotic and 44 dizygotic, age median and Q1–Q3: 53 (44–63.75) years) adult twins from the Hungarian Twin Registry. We completed cephalometric, soft tissue and fatty tissue space measurements on T1- and T2-weighted images in sagittal, coronal and axial planes. For the analysis of the genetic and environmental, the determination of the measured parameters was performed with an ACE twin statistical model. Results: We found a strong genetic determination in the anteroposterior diameter of the tongue and the thickness of the submental fatty tissue of the neck. Other parameters of the tongue, soft palate and uvula have shown moderate heritability, while we found strong environmental determination in the thickness of the parapharyngeal fatty tissue, the thickness of the pharyngeal wall, and the smallest diameter of the posterior upper airways. Conclusion: Our twin study can help better understand the genetic and environmental background of anatomical structures involved in the development of sleep apnea.

Empirical assessment of allele frequencies of genome wide association study variants associated with obstructive sleep apnea

OBJECTIVE

Obstructive Sleep Apnea (OSA) is a heterogeneous disorder with a complex interplay of genetic and environmental factors. Over the years, with advancement in genotyping and sequencing techniques, various loci have shown an association with OSA. It is pertinent to understand the status of these associated variants in different ethnic groups. The aim of the study was to assess the genetic affinity among different population groups by evaluating the risk allele frequencies of variants associated with OSA.

METHOD

The variants associated with OSA were obtained from the GWAS catalog with a significant p value of <5 × 10-7; 95 variants were obtained (www.ebi.ac.uk/gwas). Further, the variants were narrowed down on the basis of risk allele frequencies (>5%). The fst was calculated to assess the genetic affinity between super population groups and among the sub-population groups present in the 1000 genome project.

RESULT

The fst values observed indicated all super populations were genetically related (SAS, AMR, EAS and EUR) except in the African (AFR) population group. Further, the closely related super population i.e., SAS, AMR, EAS and EUR when bifurcated on the basis of sub-population groups shows population stratification and SAS population groups form separate clusters on the MDS plot.

CONCLUSION

The study highlights genetic heterogeneity among different population groups that gets diluted and results are biased when the samples are pooled irrespective of their endogamous groups. Our results provide insight to researchers to target specific endogamous groups for future studies on OSA.

Gut Microbiome in Patients with Obstructive Sleep Apnoea

Background: Obstructive sleep apnoea (OSA) is a risk factor for cardiovascular disease. Alterations in the gut microbiome have been implicated in the development of cardiovascular disease and may potentially link OSA to its cardiovascular consequences. However, only one study to date has investigated gut microbiomes in adult patients with OSA. Methods: 19 patients with OSA and 20 non-OSA controls participated in the study. Following a diagnostic sleep study, blood was collected for metabolic profiling, and the subjects provided a stool sample for microbiome analysis. The gut microbiome was investigated using the 16S ribosomal RNA method. Results: Patients with OSA had a higher relative abundance of the Proteobacteria phylum (p = 0.03), Gammaproteobacteria class (p = 0.01), Lactobacillae family (p = 0.02), Lactobacillus (p = 0.03), and Roseburia genus (p = 0.03), and a lower abundance of the Actinobacteria phylum (p = 0.03). The abundance of Proteobacteria, Gammaproteobacteria, Lactobacillae, and Lactobacillus were related to disease severity and dyslipidaemia (all p < 0.05), whilst the abundance of Proteobacteria and Gammaproteobacteria was also related to hypertension and cardiovascular disease (all p < 0.05). However, following adjustment for relevant confounders only the association between OSA and Actinobacteria remained significant (p = 0.04). Conclusions: Obstructive sleep apnoea is associated with only subtle changes in gut microbiome. Further studies should investigate gut dysbiosis in OSA.

Excessive daytime sleepiness: an emerging marker of cardiovascular risk

Excessive daytime sleepiness (EDS) is classically viewed as a consequence of insufficient sleep or a symptom of sleep disorders. Epidemiological and clinical evidence have shown that patients reporting EDS in tandem with sleep disorders (e.g., obstructive sleep apnoea) are at greater cardiovascular risk than non-sleepy patients. While this may simply be attributable to EDS being present in patients with a more severe condition, treatment of sleep disorders does not consistently alleviate EDS, indicating potential aetiological differences. Moreover, not all patients with sleep disorders report EDS, and daytime sleepiness may be present even in the absence of any identifiable sleep disorder; thus, EDS could represent an independent pathophysiology. The purpose of this review is twofold: first, to highlight evidence that EDS increases cardiovascular risk in the presence of sleep disorders such as obstructive sleep apnoea, narcolepsy and idiopathic hypersomnia and second, to propose the notion that EDS may also increase cardiovascular risk in the absence of known sleep disorders, as supported by some epidemiological and observational data. We further highlight preliminary evidence suggesting systemic inflammation, which could be attributable to dysfunction of the gut microbiome and adipose tissue, as well as deleterious epigenetic changes, may promote EDS while also increasing cardiovascular risk; however, these pathways may be reciprocal and/or circumstantial. Additionally, gaps within the literature are noted followed by directions for future research.

Variants of candidate genes associated with the risk of obstructive sleep apnea

BACKGROUND

The researches on the associations between different candidate genes and obstructive sleep apnea (OSA) are inconsistent. Here, we performed a comprehensive qualitative and quantitative analysis to estimate the contribution of variants from candidate genes to the risk of OSA.

METHODS

Qualitative analysis was conducted to find the relationships for all included genes. Then, quantitative analysis of both allele models and genotype models was applied to evaluate the risk variants for OSA. Furthermore, a similar analysis was performed in different ethnic groups.

RESULTS

We included 152 publications containing 75 genes for qualitative analysis. Among them, we included 93 articles containing 28 variants from 16 genes for quantitative analysis. Through allele models, we found 10 risk variants for OSA (rs1801133 of MTHFR, ɛ4 of ApoE, -1438G/A of 5-HT2A, -308G/A of TNF-α, Pro1019Pro of LEPR, rs1130864 and rs2794521 of CRP, D/I of ACE, LPR and VNTR of 5-HTT) with the ORs of 1.21-2.07 in global population. We found that the variant of ɛ2 of ApoE could uniquely decrease the risk of OSA in the East Asian subgroup, while the other 6 variants, including ɛ4 in ApoE, -308G/A in TNF-α, Pro1019Pro in LEPR, D/I in ACE, LPR and VNTR in 5-HTT, could increase the risk of OSA. As for the European subpopulation, we only found that -308G/A in TNF-α could increase the risk for OSA.

CONCLUSIONS

Eleven variants from the candidate genes are associated with the risk of OSA, which also show ethnicity differences in East Asian and European subgroups.

Obstructive sleep apnea and associated factors among hypertensive patients attending a tertiary cardiac center in Tanzania: a comparative cross-sectional study

Background

There is mounting evidence for a reciprocal yet bidirectional association between sleep-disordered breathing and hypertension. Obstructive sleep apnea (OSA), a common cause of systemic hypertension is an independent risk factor for hypertension-related cardiovascular morbidity and mortality. In this comparative hospital-based cross-sectional study, we sought to explore the burden of obstructive sleep apnea and its associated risk factors among hypertensive patients attending Jakaya Kikwete Cardiac Institute.

Methodology

A total of 1974 individuals (i.e. 1289 hypertensive and 685 normotensives) were consecutively enrolled in this study. The Berlin questionnaire and Epworth Sleepiness Scale were utilized in the assessment of OSA and excessive daytime sleepiness (EDS) respectively. Logistic regression analyses were employed in the determination of associated factors for OSA.

Results

The mean age was 53.4 years and females constituted the large majority (60.4%) of participants. About three quarters (74.1%) of participants had excess body weight, 11.6% had diabetes, 8.0% had asthma and 18.6% had history of recurrent nasal congestion. Positive family history of snoring was reported by 43.1% of participants and 36.9% had a personal history of snoring. Persons with hypertension displayed a higher frequency (42.1%) of OSA compared to their normotensive counterparts (11.8%), p < 0.001. Multivariate logistic regression analyses revealed hypertension (OR 5.1, 95% CI 3.2-8.2, p < 0.001), diabetes mellitus (OR 2.2, 95% CI 1.3-3.5, p < 0.01), chronic nasal congestion (OR 1.6, 95% CI 1.1-2.5, p = 0.01), obesity (OR 2.4, 95% CI 1.8-3.3, p < 0.001), increased neck circumference (OR 2.7, 95% CI 1.2-6.4, p = 0.02), family history of snoring (OR 5.5, 95% CI 4.0-7.5, p < 0.001), and working > 8 h/24 h (OR 0.6, 95% CI 0.4-1.0, p = 0.03) to have an independent association for OSA. Furthermore, participants with hypertension displayed superior odds for OSA compared to their normotensive counterparts across all subgroup analyses.

Conclusion

OSA is considerably common among patients with hypertension in a tertiary health care setting in Tanzania. Positive family history of snoring was the strongest associated factor; however, excess body weight proved to be the strongest modifiable risk factor. In view of its pervasiveness, OSA should be an integral part of the medical evaluation in hypertensive individuals.

Lumbar spine abnormalities in patients with obstructive sleep apnoea

Previous studies suggested cervical spondylosis as a risk factor for development of obstructive sleep apnoea (OSA). We aimed to assess lumbar disc degeneration in patients with OSA and correlate the findings with symptoms and disease severity. Twenty-seven patients with OSA and 29 non-OSA controls underwent sleep studies and lumbar magnetic resonance imaging (MRI), and completed the Epworth Sleepiness Scale and the 24-item Roland-Morris Disability Questionnaire (RMDQ) questionnaires. Plasma klotho was determined with enzyme-linked immunosorbent assay. Patients with OSA had higher number of disc bulges (4.6 ± 3.7 vs. 1.7 ± 2.5, p < 0.01) and anterior spondylophytes (2.7 ± 4.2 vs. 0.8 ± 2.1, p < 0.01), increased disc degeneration (total Pfirrmann score 16.7 ± 4.7 vs. 13.2 ± 4.1, p < 0.01) and vertebral fatty degeneration (7.8 ± 4.7 vs. 3.8 ± 3.7, p < 0.01). There was no difference in the RMDQ score (0/0-3.5/ vs. 0/0-1/, p > 0.05). Markers of OSA severity, including the oxygen desaturation index and percentage of total sleep time spent with saturation < 90% as well as plasma levels of klotho were correlated with the number of disc bulges and anterior spondylophytes (all p < 0.05). OSA is associated with lumbar spondylosis. Our study highlights the importance of lumbar imaging in patients with OSA reporting lower back pain.

Polysomnographic Characteristics of Snoring Children: A Familial Study of Obstructive Sleep Apnea Syndrome

BACKGROUND AND OBJECTIVES

Available evidence suggests a familial basis for OSA. The aim of the present study was to assess the potential influences of parental OSA in predicting the diagnosis and severity of OSA in snoring children.

METHODS

Observational study, we prospectively enrolled 84 children and their parents. A complete nocturnal polysomnography was performed. Children were categorized into 3 severity groups according to the apnea-hypopnea index (AHI<1h^-1, AHI≥1h^-1 to AHI<5h^-1, and AHI≥5h^-1). Adults were grouped according two criteria (AHI≥5h^-1 and ≥10h^-1).

RESULTS

There were no significant differences in age, gender, BMI and BMI z-score among groups. Among the children, 54.7% had an AHI≥1h^-1 and 21.4% had an AHI≥5h^-1. Overall, we observed that 60.7% of fathers and 23.8% of mothers of our population had OSA (AHI≥5h^-1). The prevalence of fathers with OSA increases with the children's severity (83% in the group of children with moderate-severe OSA, p=0.035). The odds of having moderate-severe pediatric OSA (AHI≥5h^-1) were more than 4 times higher among children with a father with AHI≥5h^-1 (OR: 4.92, 95% CI: 1.27-19.06; p=0.021). There was no evidence of any maternal influence on OSA severity among the children studied.

CONCLUSIONS

Our findings suggest a high prevalence of OSA among the family members studied with an increased association of childhood OSA with paternal OSA. Prediction of OSA risk among children can be significantly improved by adding data on paternal OSA status.

Inference of causal relationships between sleep-related traits and 1,527 phenotypes using genetic data

STUDY OBJECTIVE

Sleep is essential for both physical and mental health, and there is a growing interest in understanding how different factors shape individual variation in sleep duration, quality and patterns, or confer risk for sleep disorders. The present study aimed to identify novel inferred causal relationships between sleep-related traits and other phenotypes, using a genetics-driven hypothesis-free approach not requiring longitudinal data.

METHODS

We used summary-level statistics from genome-wide association studies and the latent causal variable (LCV) method to screen the phenome and infer causal relationships between seven sleep-related traits (insomnia, daytime dozing, easiness of getting up in the morning, snoring, sleep duration, napping, and morningness) and 1,527 other phenotypes.

RESULTS

We identify 84 inferred causal relationships. Among other findings, connective tissue disorders increase insomnia risk and reduce sleep duration; depression-related traits increase insomnia and daytime dozing; insomnia, napping, and snoring are affected by obesity and cardiometabolic traits and diseases; and working with asbestos, thinner, or glues may increase insomnia risk, possibly through an increased risk of respiratory disease or socio-economic related factors.

CONCLUSION

Overall, our results indicate that changes in sleep variables are predominantly the consequence, rather than the cause, of other underlying phenotypes and diseases. These insights could inform the design of future epidemiological and interventional studies in sleep medicine and research.

Molecular determinants of obstructive sleep apnea

Obstructive sleep apnea (OSA) is characterized as recurrent episodes of obstruction in the upper airway during the period of sleep. The condition occurs in approximately 11% and 4% of middle-aged men and middle-aged women, respectively. Polysomnography is a diagnostic procedure that involves the constant observation of oxygen saturation and unsaturation during sleep. Usually, positive airway pressure is considered a benchmark treatment for OSA. This review summarizes the recent developments and emerging evidence from molecular biology-based research studies that show that genetic factors have an influence on OSA. The genetic aspects of OSA that have been identified include heritability and other phenotypic co-factors such as anatomical morphology. It also draws attention to the results of a polymorphic-based study that was conducted to determine the causative single nucleotide mutations associated with obesity and adverse cardiovascular risk in OSA. However, the role of such mutations and their linkage to OSA can not yet be established. Nonetheless, a large body of evidence supports a strong association between inflammatory cytokine polymorphism and obesity in the development of OSA. There are also probable intermediate factors with several gene-gene interactions. Therefore, advanced applications and modern techniques should be applied to facilitate new findings and to minimize the risk of developing OSA.

Association between long-term exposure to ambient air pollutants and excessive daytime sleepiness in Chinese rural population: The Henan Rural Cohort Study

BACKGROUND

Excessive daytime sleepiness is associated with many adverse consequences, including cardiovascular diseases and mortality. Although exposure to air pollution has been suggested in connection with excessive daytime sleepiness, evidence in China is scarce. The study aimed to explore the association between long-term exposure to air pollution and excessive daytime sleepiness in rural China.

METHODS

A lot of 27935 participants (60% females) from the Henan Rural Cohort Study were included in this analysis. A satellite-based spatiotemporal model estimated a 3-year average air pollution exposure to NO₂ (nitrogen dioxide), PM₁ (particulate matter with aerodynamic diameters not more than 1 μm) and PM_2.5 (particulate matter with aerodynamic diameters not more than 2.5 μm) at the home address of participants before the baseline survey. Logistic regression was used to evaluate the odds ratio and 95% confidence interval between long-term air pollution and excessive daytime sleepiness.

RESULTS

The average concentrations of NO₂, PM₁ and PM_2.5 during three years preceding baseline survey were 38.22 μg/m³, 56.29 μg/m³ and 72.30 μg/m³. Exposure to NO₂, PM₁ and PM_2.5 were all associated with excessive daytime sleepiness. Each 1 μg/m³ increment of NO₂, PM₁ and PM_2.5 were related to a 20% (OR: 1.20, 95% CI: 1.13-1.27), 10% (OR: 1.10, 95% CI: 1.05-1.16) and 17% (OR: 1.17, 95% CI: 1.10-1.23) increase of the prevalence of excessive daytime sleepiness.

CONCLUSION

The study demonstrated that long-term exposure to NO₂, PM₁ and PM_2.5 were all associated with excessive daytime sleepiness. The impact of air pollution should be considered when treating individuals with excessive daytime sleepiness.

Polysomnographic Characteristics of Snoring Children: A Familial Study of Obstructive Sleep Apnea Syndrome

BACKGROUND AND OBJECTIVES

Available evidence suggests a familial basis for OSA. The aim of the present study was to assess the potential influences of parental OSA in predicting the diagnosis and severity of OSA in snoring children.

METHODS

Observational study, we prospectively enrolled 84 children and their parents. A complete nocturnal polysomnography was performed. Children were categorized into 3 severity groups according to the apnea-hypopnea index (AHI<1h^-1, AHI≥1h^-1 to AHI<5h^-1, and AHI≥5h^-1). Adults were grouped according two criteria (AHI≥5h^-1 and ≥10h^-1).

RESULTS

There were no significant differences in age, gender, BMI and BMI z-score among groups. Among the children, 54.7% had an AHI≥1h^-1 and 21.4% had an AHI≥5h^-1. Overall, we observed that 60.7% of fathers and 23.8% of mothers of our population had OSA (AHI≥5h^-1). The prevalence of fathers with OSA increases with the children's severity (83% in the group of children with moderate-severe OSA, p=0.035). The odds of having moderate-severe pediatric OSA (AHI≥5h^-1) were more than 4 times higher among children with a father with AHI≥5h^-1 (OR: 4.92, 95% CI: 1.27-19.06; p=0.021). There was no evidence of any maternal influence on OSA severity among the children studied.

CONCLUSIONS

Our findings suggest a high prevalence of OSA among the family members studied with an increased association of childhood OSA with paternal OSA. Prediction of OSA risk among children can be significantly improved by adding data on paternal OSA status.

The Hungarian Twin Registry Update: Turning From a Voluntary to a Population-Based Registry

Since our last report on the voluntary Hungarian Twin Registry (HTR) in 2012, the number of pairs or multiplets included increased from 310 to 1044. Efforts to turn the registry into a population-based one are on the way. Nearly 128,000 twins living in Hungary (98,500 adults) will be mailed information on how to register on the new HTR website. Twins will be asked to invite their spouses and immediate family members. Meanwhile, strong cooperation through exchange programs has been developed with other foreign twin registries. Current research focuses on radiogenomics, musculoskeletal, cardiovascular and respiratory diseases, gut microbiome as well as basic molecular research and yielded new awards and further publications.

Obstructive sleep apnea and hypertriglyceridaemia share common genetic background: Results of a twin study

Obstructive sleep apnea is associated with an increased risk of hypertension, diabetes and dyslipidaemia. Both obstructive sleep apnea and its comorbidities are at least partly heritable, suggesting a common genetic background. Our aim was to analyse the heritability of the relationship between obstructive sleep apnea and its comorbidities using a twin study. Forty-seven monozygotic and 22 dizygotic adult twin pairs recruited from the Hungarian Twin Registry (mean age 51 ± 15 years) attended an overnight diagnostic sleep study. A medical history was taken, blood pressure was measured, and blood samples were taken for fasting glucose, total cholesterol, triglyceride, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol and lipoprotein (a). To evaluate the heritability of obstructive sleep apnea and its comorbidities bivariate analysis was performed with an adjustment for age, gender, body mass index (BMI) and smoking after false discovery rate correction and following exclusion of patients on lipid-lowering and antidiabetic medications. There was a significant correlation between indices of obstructive sleep apnea severity, such as the apnea-hypopnea index, oxygen desaturation index and percentage of sleep time spent with oxygen saturation below 90%, as well as blood pressure, serum triglyceride, lipoprotein (a) and glucose levels (all p < .05). The bivariate analysis revealed a common genetic background for the correlations between serum triglyceride and the oxygen desaturation index (r = .63, p = .03), as well as percentage of sleep time spent with oxygen saturation below 90% (r = .58, p = .03). None of the other correlations were significantly genetically or environmentally determined. This twin study demonstrates that the co-occurrence of obstructive sleep apnea with hypertriglyceridaemia has a genetic influence and heritable factors play an important role in the pathogenesis of dyslipidaemia in obstructive sleep apnea.