Nocturnal Mean Oxygen Saturation Is Associated with Secondary Polycythemia in Young Adults with Obstructive Sleep Apnea, Especially in Men

The relationship between haemoglobin concentrations and obstructive sleep apnea syndrome: A systematic review and meta-analysis

BACKGROUND

This systematic review and meta-analysis investigates the relationship between haemoglobin (Hb) concentrations and obstructive sleep apnea syndrome (OSAS).

METHODS

Following PRISMA guidelines, we searched PubMed, EMBASE, and Cochrane Library from inception to March 8, 2024. Eligible studies included cross-sectional, cohort, and case-control designs comparing Hb concentrations in OSAS patients and healthy controls. Two reviewers independently screened records and extracted data. The risk of bias was assessed using the Joanna Briggs Institute checklist.

RESULTS

A total of 27 studies involving 6499 OSAS subjects and 5199 controls were included. Hb concentrations were significantly higher in OSAS patients compared to controls (SMD: 0.28; 95 % CI: 0.18 to 0.39; I2 = 84.4 %). Subgroup analysis by OSAS severity showed that severe OSAS patients had higher Hb concentrations than those with mild/moderate OSAS. Sensitivity analyses confirmed the robustness of the findings. However, 7 studies reported opposite results, indicating possible regional or methodological differences.

CONCLUSION

Hb concentrations are elevated in OSAS patients, with higher levels observed in severe cases. The significant heterogeneity and the predominance of studies from Turkey highlight the need for further research in diverse populations. Limitations include potential publication bias and variability in study designs.

COVID-19 and silent hypoxemia in a minimal closed-loop model of the respiratory rhythm generator

Silent hypoxemia, or "happy hypoxia," is a puzzling phenomenon in which patients who have contracted COVID-19 exhibit very low oxygen saturation ( SaO 2 < 80%) but do not experience discomfort in breathing. The mechanism by which this blunted response to hypoxia occurs is unknown. We have previously shown that a computational model of the respiratory neural network (Diekman et al. in J Neurophysiol 118(4):2194-2215, 2017) can be used to test hypotheses focused on changes in chemosensory inputs to the central pattern generator (CPG). We hypothesize that altered chemosensory function at the level of the carotid bodies and/or the nucleus tractus solitarii are responsible for the blunted response to hypoxia. Here, we use our model to explore this hypothesis by altering the properties of the gain function representing oxygen sensing inputs to the CPG. We then vary other parameters in the model and show that oxygen carrying capacity is the most salient factor for producing silent hypoxemia. We call for clinicians to measure hematocrit as a clinical index of altered physiology in response to COVID-19 infection.

Idiopathic erythrocytosis: A diagnostic and management challenge with emerging areas for exploration

Despite published algorithms for approaching the work-up of erythrocytosis, a significant proportion of patients are left with uncertainty as to its aetiology and prognosis. The term 'idiopathic erythrocytosis' (IE) is applied when known primary and secondary aetiologies have been ruled out. However, the assignment of secondary aetiologies is not always straightforward or evidence based, which can lead to misdiagnosis and heterogeneity in cohort studies. Furthermore, new studies have identified germline or somatic mutations that may affect prognosis. Epidemiological and cohort data are inconsistent as to whether IE increases the risk for complications such as arterial and venous thromboembolism, clonal transformation or comorbid conditions. Randomized trials assessing the role of phlebotomy for long-term management of IE have not been performed, so treatment remains a vexing problem for clinicians. Standardization of terminology and testing strategies, including comprehensive genetic screening in clinical research, are key to refining our understanding of IE.

Distraction Osteogenesis as a reliable method in management of Obstructive Sleep Apnoea (OSA) secondary to TMJ Ankylosis: A Case Report

Obstructive sleep apnoea (OSA) is identified as repetitive and intermittent upper airway collapse or narrowing during sleep. Skeletal advancement through maxillomandibular surgery remains the most effective surgical treatment for OSA but is radical with certain relapse rate. Distraction Osteogenesis of mandible is a single-jaw surgical treatment alternative to bi-jaw surgeries having lesser complications. This case report describes successful management of a 46-year-old patient who reported with a chief complain of obstruction in breathing while sleeping since one year. Obstructive Sleep Apnoea (OSA) secondary to a retrognathic mandible was the final diagnosis, which was successfully treated by Distraction Osteogenesis (DO) of the mandible. The case showed enhancement in airway by 13mm and marked forward movement of Point-B (SNB increased by 6 degrees). The Epworth Sleepiness Scale value decreased from 19mm to 8 mm indicating substantial increase in the airway with stable results after 18 months of follow-up (elimination of symptoms and subsequent sound sleep). Distraction osteogenesis is an effective and reliable method to treat obstructive sleep apnoea secondary to retrognathic mandible.

JAK2 unmutated erythrocytosis: 2023 Update on diagnosis and management

DISEASE OVERVIEW

JAK2 unmutated or non-polycythemia vera (PV) erythrocytosis encompasses a heterogenous spectrum of hereditary and acquired entities.

DIAGNOSIS

Foremost in the evaluation of erythrocytosis is the exclusion of PV through JAK2 (inclusive of exons 12-15) mutation screening. Initial assessment should also include gathering of previous records on hematocrit (Hct) and hemoglobin (Hgb) levels, in order to streamline the diagnostic process by first distinguishing longstanding from acquired erythrocytosis; subsequent subcategorization is facilitated by serum erythropoietin (Epo) measurement, germline mutation screening, and review of historical data, including comorbid conditions and medication list. Hereditary erythrocytosis constitutes the main culprit in the context of longstanding erythrocytosis, especially when associated with a positive family history. In this regard, a subnormal serum Epo level suggests EPO receptor mutation. Otherwise, considerations include those associated with decreased (high oxygen affinity Hgb variants, 2,3-bisphosphoglycerate deficiency, PIEZO1 mutations, methemoglobinemia) or normal oxygen tension at 50% Hgb saturation (P50). The latter include germline oxygen sensing pathway (HIF2A-PHD2-VHL) and other rare mutations. Acquired erythrocytosis commonly results from central (e.g., cardiopulmonary disease, high-altitude habitat) or peripheral (e.g., renal artery stenosis) hypoxia. Other noteworthy conditions associated with acquired erythrocytosis include Epo-producing tumors (e.g., renal cell carcinoma, cerebral hemangioblastoma) and drugs (e.g., testosterone, erythropoiesis stimulating agents, sodium-glucose cotransporter-2 inhibitors). Idiopathic erythrocytosis is an ill-defined terminology that presumes the existence of an increased Hgb/Hct level without an identifiable etiology. Such classification often lacks accounting for normal outliers and is marred by truncated diagnostic evaluation.

MANAGEMENT

Current consensus treatment guidelines are not supported by hard evidence and their value is further undermined by limited phenotypic characterization and unfounded concerns for thrombosis. We are of the opinion that cytoreductive therapy and indiscriminate use of phlebotomy should be avoided in the treatment of non-clonal erythrocytosis. However, it is reasonable to consider therapeutic phlebotomy if one were to demonstrate value in symptom control, with frequency determined by symptoms rather than Hct level. In addition, cardiovascular risk optimization and low dose aspirin is often advised.

FUTURE DIRECTIONS

Advances in molecular hematology might result in better characterization of "idiopathic erythrocytosis" and expansion of the repertoire for germline mutations in hereditary erythrocytosis. Prospective controlled studies are needed to clarify potential pathology from JAK2 unmutated erythrocytosis, as well as to document the therapeutic value of phlebotomy.

COVID-19 and silent hypoxemia in a minimal closed-loop model of the respiratory rhythm generator

Silent hypoxemia, or 'happy hypoxia', is a puzzling phenomenon in which patients who have contracted COVID-19 exhibit very low oxygen saturation (SaO2 < 80%) but do not experience discomfort in breathing. The mechanism by which this blunted response to hypoxia occurs is unknown. We have previously shown that a computational model (Diekman et al., 2017, J. Neurophysiol) of the respiratory neural network can be used to test hypotheses focused on changes in chemosensory inputs to the central pattern generator (CPG). We hypothesize that altered chemosensory function at the level of the carotid bodies and/or the nucleus tractus solitarii are responsible for the blunted response to hypoxia. Here, we use our model to explore this hypothesis by altering the properties of the gain function representing oxygen sensing inputs to the CPG. We then vary other parameters in the model and show that oxygen carrying capacity is the most salient factor for producing silent hypoxemia. We call for clinicians to measure hematocrit as a clinical index of altered physiology in response to COVID-19 infection.

Rearrangement of cell types in the rat carotid body neurogenic niche induced by chronic intermittent hypoxia

The carotid body (CB) is a prototypical acute oxygen (O₂ )-sensing organ that mediates reflex hyperventilation and increased cardiac output in response to hypoxaemia. CB overactivation, secondary to the repeated stimulation produced by the recurrent episodes of intermittent hypoxia, is believed to contribute to the pathogenesis of sympathetic hyperactivity present in sleep apnoea patients. Although CB functional plasticity induced by chronic intermittent hypoxia (CIH) has been demonstrated, the underlying mechanisms are not fully elucidated. Here, we show that CIH induces a small increase in CB volume and rearrangement of cell types in the CB, characterized by a mobilization of immature quiescent neuroblasts, which enter a process of differentiation into mature, O₂ -sensing and neuron-like, chemoreceptor glomus cells. Prospective isolation of individual cell classes has allowed us to show that maturation of CB neuroblasts is paralleled by an upregulation in the expression of specific glomus cell genes involved in acute O₂ -sensing. CIH enhances mitochondrial responsiveness to hypoxia in maturing neuroblasts as well as in glomus cells. These data provide novel perspectives on the pathogenesis of CB-mediated sympathetic overflow that may lead to the development of new pharmacological strategies of potential applicability in sleep apnoea patients. KEY POINTS: Obstructive sleep apnoea is a frequent condition in the human population that predisposes to severe cardiovascular and metabolic alterations. Activation of the carotid body, the main arterial oxygen-sensing chemoreceptor, by repeated episodes of hypoxaemia induces exacerbation of the carotid body-mediated chemoreflex and contributes to sympathetic overflow characteristic of sleep apnoea patients. In rats, chronic intermittent hypoxaemia induces fast neurogenesis in the carotid body with rapid activation of neuroblasts, which enter a process of proliferation and maturation into O₂ -sensing chemoreceptor glomus cells. Maturing carotid body neuroblasts and glomus cells exposed to chronic intermittent hypoxia upregulate genes involved in acute O₂ sensing and enhance mitochondrial responsiveness to hypoxia. These findings provide novel perspectives on the pathogenesis of carotid body-mediated sympathetic hyperactivation. Pharmacological modulation of carotid body fast neurogenesis could help to ameliorate the deleterious effects of chronic intermittent hypoxaemia in sleep apnoea patients.

The Overlap Syndrome of Obstructive Sleep Apnea and Chronic Obstructive Pulmonary Disease: A Systematic Review

Chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea (OSA) are common diseases that strongly impact the quality and length of life. Their coexistence is determined by overlap syndrome (OS). This systematic review aims to define the significance of these comorbidities according to the current state of knowledge. For this systematic review, we searched PubMed, Scopus, and Cochrane for studies published between 2018 and 26 October 2022, to find original, observational, human studies published in English, where the diagnosis of COPD was according to the Global Initiative for Obstructive Lung Disease guidelines and the diagnosis of OSA was based on polysomnography. The quality of studies was assessed using the Newcastle-Ottawa quality assessment tool for cohort and case-control studies, as well as its modification for cross-sectional studies. Of the 1548 records identified, 38 were eligible and included in this systematic review. The included studies covered a total population of 27,064 participants. This paper summarizes the most important, up-to-date information regarding OS, including the prevalence, meaning of age/gender/body mass index, polysomnography findings, pulmonary function, comorbidities, predicting OSA among COPD patients, and treatment of this syndrome.

Prevalence of elevated hemoglobin and hematocrit levels in patients with obstructive sleep apnea and the impact of treatment with continuous positive airway pressure: a meta-analysis

OBJECTIVES

Obstructive sleep apnea (OSA) is reported to be a cause of secondary polycythemia. The present study (i) reviewed the literature reporting the prevalence of secondary polycythemia in patients with OSA and (ii) determined the effect of continuous positive airway pressure (CPAP) therapy on hemoglobin and hematocrit levels in patients with OSA.

METHODS

We searched MEDLINE, Embase and Cochrane for studies of adult patients with OSA that reported hemoglobin and/or hematocrit levels. We performed summary estimates of (i) polycythemia prevalence and a subgroup analysis according to OSA severity, and (ii) change in hemoglobin and hematocrit levels following treatment with CPAP.

RESULTS

Synthesis of seven studies including 3,654 patients revealed an overall polycythemia prevalence of 2% (95% CI 1-4%); 2% (95% CI 1-3%) in mild-to moderate and 6 % (95% CI 3-12%) in severe OSA. In the pooled analysis of ten single-arm trials including 434 patients, CPAP treatment reduced hemoglobin by 3.76 g/L (95% CI -4.73 to -2.80 g/L). Similarly, pooled analysis of ten single-arm trials including 356 patients without baseline polycythemia showed that CPAP treatment reduced hematocrit by 1.1% (95% CI -1.4 to -0.9%).

CONCLUSION

Our pooled analysis supports an increased prevalence of secondary polycythemia in OSA. This estimated prevalence is likely underestimated due to the change in the polycythemia diagnostic criteria in 2016. Future randomized controlled trials are needed to evaluate the effect of CPAP in patients with baseline polycythemia.

HIGHLIGHTS

Pooled analysis shows OSA is associated with an increased prevalence of secondary polycythemiaPrevalence of polycythemia is greater in severe OSACPAP treatment for OSA reduces both the hemoglobin and hematocrit.

ABOSA - Freely available automatic blood oxygen saturation signal analysis software: Structure and validation

BACKGROUND AND OBJECTIVE

Many sleep recording software used in clinical settings have some tools to automatically analyze the blood oxygen saturation (SpO₂) signal by detecting desaturations. However, these tools are often inadequate for scientific research as they do not provide SpO₂ signal-based parameters which are superior in the estimation of sleep apnea severity and related medical consequences. In addition, these software require expensive licenses and they lack batch analysis tools. Thus, we developed the first freely available automatic blood oxygen saturation analysis software (ABOSA) that provides sophisticated SpO₂ signal-based parameters and enables batch analysis of large datasets.

METHODS

ABOSA was programmed with MATLAB. ABOSA automatically detects desaturation and recovery events from the SpO₂ signals (EDF files) and calculates numerous parameters, such as oxygen desaturation index (ODI) and desaturation severity (DesSev). The accuracy of the ABOSA software was evaluated by comparing its desaturation scorings to manual scorings in Kuopio (n = 1981) and Loewenstein (n = 930) sleep apnea patient datasets. Validation was performed in a second-by-second manner by calculating Matthew's correlation coefficients (MCC) and median differences in parameter values. Finally, the performance of the ABOSA software was compared to two commercial software, Noxturnal and Profusion, in 100 patient subpopulations. As Noxturnal or Profusion does not calculate novel desaturation parameters, these were calculated with custom-made functions.

RESULTS

The agreements between ABOSA and manual scorings were great in both Kuopio (MCC = 0.801) and Loewenstein (MCC = 0.898) datasets. However, ABOSA slightly overestimated the desaturation parameter values. The median differences in ODIs were 0.8 (Kuopio) and 0.0 (Loewenstein) events/h. Similarly, the median differences in DesSevs were 0.02 (Kuopio) and 0.01 (Loewenstein) percentage points. In a second-by-second analysis, ABOSA performed very similarly to Noxturnal and Profusion software in both Kuopio (MCC_ABOSA = 0.807, MCC_Noxturnal = 0.807, MCC_Profusion = 0.811) and Loewenstein (MCC_ABOSA = 0.904, MCC_Noxturnal = 0.911, MCC_Profusion = 0.871) datasets. Based on Noxturnal and Profusion scorings, the desaturation parameter values were similarly overestimated compared to ABOSA.

CONCLUSIONS

ABOSA is an accurate and freely available software that calculates both traditional clinical parameters and novel parameters, provides a detailed characterization of desaturation and recovery events, and enables batch analysis of large datasets. These are features that no other software currently provides making ABOSA uniquely suitable for scientific research use.

[Analysis of related factors in secondary erythrocytosis of obstructive sleep apnea hypopnea syndrome in Gansu province]

Objective:To analyze the related factors of secondary erythrocytosis of obstructive sleep apnea（OSA） in Gansu province. Methods:Polysomnography recording and analysis from January 2013 to January 2021, A total of 448 OSA patients of long-resident Han nationality in Gansu province. Hemoglobin（Hb） values were divided into group A（Hb 120-160 g/L） 41 cases, B（Hb 161-179 g/L） 142 cases, C（Hb 180-199 g/L） 152 cases, D（Hb 200-219 g/L） 79 cases, and E（Hb ≥220 g/L） 30 cases. General clinical data, altitude of residence, disease course, apnea hypopnea index （AHI）, and Lowest oxyhemoglobin（LSpO₂） were compared among these groups. Multivariate regression and ROC curves were used to analyze the influencing factors of OSA secondary erythrocytosis. Results:There were no significant differences in age, sex, and course of disease among groups A, B, C, D, and E （P>0.05）.The altitude of group E was higher than that of groups A, B, C, and D （P<0.05）, but there was no significant difference between groups A, B, C and D （P>0.05）.AHI was significantly different among groups A, B, C, D, and E （P<0.05）, groups C, D, and E were significantly higher than A; group D was significantly higher than B, C.LSpO₂ was significantly different among groups A, B, C, D, and E （P <0.05）, groups B, C, D, and E was significantly lower than A; group D, E was significantly lower than B, C.MSpO₂ was significantly different among groups A, B, C, D, and E （P<0.05）, groups B, C, D, and E was significantly lower A; groups D, E was significantly lower than B , C.Multivariate regression showed that the higher the altitude, the lower the MSpO₂, the more serious the secondary hyperhemoglobinemia.Age, course of the disease, AHI, and LSpO₂ were not the influencing factors of OSA secondary hemoglobin increase.The areas under the ROC curve for MSpO₂ and altitude to predict Hb≥180 g/L were 0.694（P<0.001） and 0.570（P=0.009）, with statistically significant differences（Z=3.205, P=0.001）. Conclusion:Altitude and MSpO₂ were independent risk factors for OSA secondary erythrocytosis; MSpO₂ predicted that Hb≥180 g/L in OSA patients was better than altitude.

Is obstructive sleep apnea associated with erythrocytosis? A systematic review and meta‐analysis

Objective

The aim of this systematic review and meta‐analysis was to investigate the association between obstructive sleep apnea (OSA) and erythrocytosis.

Methods

The PubMed, Web of Science, and Cochrane Library databases were searched for articles examining hematocrit values in patients with OSA and control individuals published till September 1, 2021. The pooled standardized mean difference (SMD) with 95% confidence interval (CI) was calculated, and subgroup analyses were performed.

Results

Eleven eligible studies with a total of 4608 patients with OSA were included in this meta‐analysis. Pooled outcomes revealed that hematocrit values were significantly higher in patients with OSA than in controls (SMD, 0.19; 95% CI, 0.08–0.29; p < .01). When studies were stratified by disease severity, the significant differences in hematocrit values between patients and controls were only observed in the severe OSA group (SMD, 0.34; 95% CI, 0.08–0.59; p < .01), but not in the mild and moderate OSA groups. In subgroup analyses according to sex and publication year, significant differences in hematocrit values between patients and controls remained stable in studies with only female patients (SMD, 0.25; 95% CI, 0.12–0.38; p < .01) and in studies published after 2012 (SMD, 0.17; 95% CI, 0.06–0.28, p < .01).

Conclusion

Our meta‐analysis revealed that the hematocrit value was significantly increased in patients with OSA, particularly in severe patients, compared with that in controls. However, the elevation was modest, and the hematocrit value is expected to be within the normal range in patients with OSA. These data suggest that OSA leads to slight increases in hematocrit but does not cause clinically significant erythrocytosis.

Obstructive Sleep Apnea is Associated with an Increased Prevalence of Polycythemia in Patients with Chronic Obstructive Pulmonary Disease

Purpose

Chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea (OSA) are associated with polycythemia. However, there still remain unanswered questions about the relationship between overlap syndrome (OVS), where OSA and COPD coexist, and polycythemia. Here, we aimed to establish the prevalence of polycythemia in OVS patients and to explore the impact of OSA on polycythemia.

Patients and Methods

Patients with COPD underwent overnight polysomnography (PSG), pulmonary function tests, echocardiography, and complete blood counts. All patients were ethnic Han Chinese and free of prolonged oral corticosteroid use, hematological system disease, severe systemic disease, and other sleep-disordered breathing. OVS was defined as COPD patients with an apnea–hypopnea index ≥15 events/h, and polycythemia was defined as an Hb >165 g/L in men and >160 g/L in women.

Results

Eight-hundred and eighty-six patients with COPD were included in the analysis. The prevalence of polycythemia was significantly higher in OVS patients than COPD-alone patients (6.4% vs 2.9%, p < 0.05). The prevalence of polycythemia increased with OSA severity (χ² = 7.885, p = 0.007), but not in GOLD grade 3–4 COPD patients (χ² = 0.190, p = 0.663). After adjusting for confounders, percentage of total sleep time with SaO₂ <90% (TS₉₀) remained independently associated with an increased odds of polycythemia (OR 1.030, 95% CI 1.015–1.046) and, with an increase in TS₉₀, the hemoglobin increased, especially in GOLD grade 1–2 patients (p < 0.05).

Conclusion

Patients with OVS have a higher prevalence of polycythemia than those with COPD alone, and TS₉₀ is an independent factor for polycythemia, especially in GOLD1-2 COPD patients.

Possible Preventative/Rehabilitative Role of Gliflozins in OSA and T2DM. A Systematic Literature Review-Based Hypothesis

Obstructive sleep apnoea (OSA) is characterized by frequent apnoea episodes during sleep due to upper airway obstruction. The present review summarizes current knowledge on inter-relationships between OSA and type 2 diabetes mellitus (T2DM) and suggests the former as a possible target for sodium-glucose co-transporter-2 inhibitors (SGLT-2i). Based on pathophysiological mechanisms underlying OSA onset and renal SGLT-2 effects, we suggest that SGLT-2i indications might expand beyond current ones, including glucose, lipids, uric acid, blood pressure, and body weight control as well as chronic heart failure and kidney disease prevention.

Can the complete blood count be used as a reliable screening tool for obstructive sleep apnea?

PURPOSE

Since hypoxia increases erythropoietin production and inflammation, the complete blood count (CBC) has been proposed as an inexpensive alternative for obstructive sleep apnea (OSA) screening. The objective of this study was to determine whether or not intermittent hypoxia and OSA severity, as measured by the mean oxygen saturation (SpO₂) and apnea-hypopnea index (AHI), affect parameters measured by the CBC.

METHODS

This retrospective study included a total of 941 surgical patients who had a pre-operative home sleep study. The pre-operative CBC was extracted from the electronic patient records. Patients were stratified according to their AHI scores, into mild (AHI ≥ 5 - < 15), moderate (AHI ≥ 15 - < 30), and severe (AHI ≥ 30) OSA groups.

RESULTS

There were 244 patients without OSA, 294 with mild, 223 with moderate, and 180 with severe OSA. Our analysis showed that hemoglobin (P = 0.010), hematocrit (P = 0.027), and basophils (P = 0.006) showed significant changes among the different severities of OSA. For mean SpO₂, there were negative associations with body mass index (r =  - 0.287; P < 0.001), age (r =  - 0.077; P = 0.021), hemoglobin (r =  - 0.208; P < 0.001), hematocrit (r =  - 0.220; P < 0.001), red blood cells (r =  - 0.107; P = 0.001), mean corpuscular volume (MCV) (r =  - 0.159; P < 0.001), mean corpuscular hemoglobin (r =  - 0.142; P < 0.001), and basophils (r =  - 0.091; P = 0.007). All analyzed parameters remained within normal clinical range. Multivariable regression identified hemoglobin, MCV, and basophils to be independent predictors of mean SpO₂ and AHI.

CONCLUSION

Hemoglobin, MCV, and basophils were independently associated with intermittent hypoxia defined by mean SpO₂ and AHI. Adding CBC parameters to other screening tools for OSA may have additional value due to its association with changes in mean SpO_2.

Sleep apnea, "the Ugly Duckling of the Cinderellas" in cardiovascular prevention and rehabilitation

Cardiovascular diseases are the leading cause of death and account for the largest share of health expenditure worldwide, mainly invested in hospital and secondary care. Prevention and rehabilitation strategies are nearly neglected, therefore "the Cinderellas," in the health-care budget. The World Health Organization has proposed cost-effective interventions to reduce the impact of cardiovascular diseases that include polydrug treatment for hypertension and diabetes, counselling, diet, exercise, and others. Obstructive sleep apnea is not even mentioned among these interventions; consequently, it could be "the Ugly Duckling of the Cinderellas." Obstructive sleep apnea (OSA) is characterized by the presence of obstructive apneas or hypopneas during sleep, accompanied by hypoxia; and it is a highly prevalent but under-diagnosed condition. Although awareness of sleep apnea has recently increased most facts about it remains ignored by many. Robust evidence suggests that OSA is associated with, or is an independent risk factor for, hypertension, cerebrovascular disease, ischemic heart disease, heart failure and arrhythmias and that its prevalence among some of these cardiovascular diseases is higher than 80%. The efficacy of continuous positive airway pressure treatment for obstructive sleep apnea has been established. If obstructive sleep apnea plays a significant role in cardiovascular diseases, then screening and timely appropriate treatment could reduce morbidity and mortality. Thus, the public health and economic impact of these conditions could be included in the "best buy" list of interventions. This narrative review discusses the relationship between OSA and cardiovascular diseases and how neglected the link is.

Effect of mild obstructive sleep apnea in mountaineers during the climb to Mount Aconcagua

OBJECTIVE

to compare mountaineers with and without asymptomatic sleep apnea (OSA) before the ascent and to study high altitude-related sleep disorders, its interaction with metabolic, neuroendocrine and immunological components.

MATERIAL AND METHODS

During an expedition to Mount Aconcagua, researchers assessed the respiratory polygraphy (RP), clinical condition and inflammatory parameters, and rhythm of cortisol secretion in mountaineers sleeping at different altitude camps.

RESULTS

8 athletes (4 women), 36 years old (25-51) participated. Baseline and final BMI were; 23.6 (20.9-28.7) and 22.77 (20.9-27.7), respectively: p<0.01. 40 valid RP recordings were analyzed. At 746 m.a.s.l. (baseline), only 2 mountaineers presented mild asymptomatic OSA. The OSA group presented baseline apnea-hypopnea index (AHI) values between 5-15 events per hour, which evidence a mild respiratory sleep disorder with AHI increased by altitude depending of central apneas and hypopneas (p<0.05) as high altitude periodic breathing pattern but no increase in obstructive apneas (p<0.01). The circadian rhythm of cortisol was maintained in all cases in which they had not received treatment with dexamethasone and their values increased with the altitude reached. Increased systolic blood pressure was observed in the OSA group.

CONCLUSION

In a context of hypobaric hypoxia, individuals with pre-existing asymptomatic OSA are prone to experiencing lower oxygen saturations and clinical deterioration.