Altitude Residence Research Articles

Differences in cardiovascular risk in the general population of low and high altitude residents in Peru. HIGH Altitude CArdiovascular REsearch Latin America Population Study (HIGHCARE-LAPS)

Abstract Introduction Living at high altitude (HA) is associated with profound changes in cardiovascular physiology, mostly caused by chronic hypoxia. Available data from high income countries (Switzerland, Austria) suggest beneficial effects of moderate altitude residence in terms of cardiovascular risk. Little is known, however, about cardiovascular risk profile in long-term residents of higher altitudes from low-income countries. Aim To compare cardiovascular risk estimated with validated score in population-based samples of permanent residents of low and high-altitude communities in Peru. Methods Study participants (adults permanently residing at either low or high altitude) were recruited by sex- and age-stratified random multistage cluster sampling from the general population of urban areas at different altitudes in Peru (lowlanders: <500 m above sea level, highlanders: cities at 3287 m, 3824 m and 4330 m). For all participants questionnaire-based information, conventional blood pressure (BP; 3 seated measurements with a validated oscillometric device) and laboratory variables were obtained. Based on the collected data atherosclerotic cardiovascular disease (ASCVD) risk was estimated according to Pooled Cohort Equations (PCE, previously calibrated in South American population). Participants below 40 years of age, with ASVCD history, with LDL-C≥190 mg/dL or on LDL-C lowering therapy were excluded from this analysis. Results The analysis included 146 lowlanders and 373 highlanders, most of whom had low 10-year ASVCD risk, with the median estimated risk being significantly higher among lowlanders. Comparisons between the groups in terms of principal variables of interest are reported in the Table. The highlanders were slightly younger, had lower BMI, conventional BP, HDL cholesterol, lower prevalence of antihypertensive medication and of diabetes, and higher heart rate. In a multivariable model the difference in ASCVD risk between lowlanders and highlanders was significant (p=0.0009) after adjusting for BMI and socio-economic variables but not after systolic BP was included in the model (p=0.800). Conclusions Residence at HA is associated with a lower estimated ASCVD risk in the general population of Peru, mainly because of lower BP levels. Considering that the prognostic value of cardiovascular risk estimates in highland populations is unknown, longitudinal cohort studies would be required to assess whether this finding is associated with a lower rate of cardiovascular events.

RESIDENCE AT HIGH ALTITUDE IS ASSOCIATED WITH LOWER CONVENTIONAL AND AMBULATORY BLOOD PRESSURE THAN LIVING AT SEA LEVEL IN THE GENERAL POPULATION OF PERU. HIGHCARE-LAPS STUDY

Objective: Acute exposure to hypoxia at high altitude (HA) leads to an increase in blood pressure (BP) in healthy individuals and in hypertensive patients. Little is known, however, about the effect of long-term HA residence on BP. Available data based on conventional BP measurements are inconsistent and no general population studies using 24-h ambulatory BP monitoring (ABPM) have been conducted. Aim of HIGHCARE-LAPS was to compare BP levels and cardiovascular risk profile among population-based samples of subjects residing in Peruvian communities living at different altitudes. BP-related data are reported in this paper. Design and method: Study participants were recruited by sex- and age-stratified random multistage cluster sampling from the general adult population residing permanently in urban areas at different altitudes in Peru (Lima, <500m, Huancayo 3287m, Juliaca 3824m, Cerro de Pasco 4330m). In all participants questionnaire-based information, conventional BP (3 seated measurements with a validated oscillometric device, HEM7121 OMRON, Japan), 24-hour ambulatory BP (A&D TM2430, Japan) and laboratory variables were obtained. Results: The study included 206 lowlanders and 595 highlanders. Highlanders were slightly younger, had lower BMI, oxygen saturation and prevalence of antihypertensive medication use and higher haematocrit. In highlanders all conventional and ambulatory BP values were lower and heart rate values higher than in lowlanders. Comparisons between lowlander and highlander samples and for individual sites at different altitudes are reported in the Table. The difference in 24-hour systolic BP between highlanders and lowlanders remained significant (7.2 mmHg, p<0.001) in a linear multiple regression model adjusting for age, sex, BMI, 24-hour heart rate, respiratory rate, and haematocrit. These covariates were selected by LASSO method from a set also including lifestyle-related variables. Conclusions: Permanent residence at high altitude is independently associated with lower conventional and ambulatory BP levels than low altitude residence in the general population of Peru. This relationship does not seem to be explained by lifestyle differences. Mechanisms behind this difference and its impact on cardiovascular risk should be further investigated. Also, comparative studies with other highland populations with different adaptive characteristics would allow to understand better the effects of HA residence on cardiovascular health.

The Clinical Investigation on Varicocele and Sperm Quality in the Tibet an Plateau of China: A Prospectively Planned Retrospective Cohort Study.

Varicoceles are a common cause of male infertility, affecting up to 35% of men undergoing fertility evaluations. This study aims to investigate the potential influence of altitude and residence time on the occurrence of varicoceles, as well as on sperm quality and sterility in plateau areas. A total of 168 patients with varicocele were enrolled in the study, and the study population was divided into groups based on their direct exposure to different high altitudes due to their living locations. The internal diameter in Quiet breath (Dr), internal diameter in Valsalva maneuver (Dv), reflux peak value, and reflux time are gradually increased accompanied with altitude elevation and residence time extension. The number of cases above 4,500 m also increased with the severity of varicocele, and the altitude of clinical types was higher than that of subclinical types of varicocele. Especially above 4,500 m, the Dv, Dr, reflux peak value, and reflux time all increased with the severity of varicocele. The severity of varicocele was positively correlated with the residence time in plateau area. Patients with residence time of more than 1 year had higher values of Dr, Dv, differentiation time, reflux peak value, and reflux time than those with residence time of less than 1 year. Compared to 3,650 m, patients with varicocele in 4,500 m also have worse semen quality. Both altitude and residence time are strongly positively related to the severity and incidence rate of varicocele in plateau areas.

Health Benefits of Residence at Moderate Altitude Do Not Reduce COVID-19 Mortality.

Moderate altitude (1000−2000 m above sea level) residence is emerging as a protective factor from the mortality of various causes, including of cardiovascular diseases. Conversely, mortality from certain respiratory diseases is higher at these altitudes than in lowlands. These divergent outcomes could indicate either beneficial or detrimental effects of altitude on the mortality of COVID-19 that primarily infects the respiratory tract but results in multi-organ damage. Previous epidemiological data indeed suggest divergent outcomes of moderate to high altitude residence in various countries. Confounding factors, such as variations in the access to clinical facilities or selection biases of investigated populations, may contribute to the equivocation of these observations. We interrogated a dataset of the complete population of an Alpine country in the center of Europe with relatively similar testing and clinical support conditions across altitude-levels of residence (up to around 2000 m) to assess altitude-dependent mortality from COVID-19 throughout 2020. While a reduced all-cause mortality was confirmed for people living higher than 1000 m, no differences in the mortality from COVID-19 between the lowest and the highest altitude regions were observed for the overall population and the population older than 60 years as well. Conversely, COVID-19 mortality seems to have been reduced in the very old (>85 years) women at moderate altitudes.

Effect of hypobaric hypoxia on hematological parameters related to oxygen transport, blood volume and oxygen consumption in adolescent endurance-training athletes

Background/ObjectiveTo analyze the effect of altitude on hematological and cardiorespiratory variables in adolescent athletes participating in aerobic disciplines. Methods21 females and 89 males participated in the study. All were adolescent elite athletes engaged in endurance sports (skating, running and cycling) belonging to two groups: permanent residents in either low altitude (LA, 966 m) or moderate altitude (MA, 2640 m). Hematocrit (Hct), hemoglobin concentration ([Hb]), total hemoglobin mass (Hbt), blood, plasma and erythrocyte volumes (BV, PV and EV), VO2peak and other cardiorespiratory parameters were evaluated. ResultsSex differences were evident both in LA and HA skating practitioners, the males having higher significant values than the females in oxygen transport-related hematological parameters and VO2peak. The effect of altitude residence was also observed in Hct, [Hb], Hbt and EV with increased (14%–18%) values in the hematological parameters and higher EV (5%–24%). These results matched the significantly higher values of VO2peak measured in MA residents. However, BV and PV did not show differences between LA and MA residents in any case. Sports discipline influenced neither the hematological variables nor most of the cardiorespiratory parameters. ConclusionsLA and MA adolescent skaters showed sex differences in hematological variables. Endurance-trained male adolescent residents at MA had an increased erythropoietic response and a higher VO2peak compared to their counterparts residing and training at LA. These responses are similar in the three aerobic sports studied, indicating that the variables described are highly sensitive to hypoxia irrespective of the sports discipline.

Moderate Altitude Residence Reduces Male Colorectal and Female Breast Cancer Mortality More Than Incidence: Therapeutic Implications?

Simple SummaryLiving at moderate altitudes has been reported to be associated with health benefits, including reduced mortality from male colorectal and female breast cancer. The aim of this study was to evaluate altitude-dependent incidence rates and to compare them with mortality rates of those cancers. We further explored whether altitude-associated differences in lifestyle behaviour exist. Analyses including all incidence cases and deaths over a 10-year observation period of an Alpine country (Austria) revealed that the age-standardized incidence and mortality rates of male colorectal cancer decreased by 24.0% and 44.2%, and that of female breast cancer by 6.5% and 26.2%, from the lowest (<251 m) to the highest (1000–2000) altitude level. The population-based survey indicated higher physical activity levels and lower body mass index for both sexes living at a moderate altitude compared to those living below 251 m. These observations may, in certain cases, support decision making when changing residence.Background: Living at moderate altitude may be associated with health benefits, including reduced mortality from male colorectal and female breast cancer. We aimed to determine altitude-dependent incidence and mortality rates of those cancers and put them in the context of altitude-associated lifestyle differences. Methods: Incidence cases and deaths of male colorectal cancer (n = 17,712 and 7462) and female breast cancer (n = 33,803 and 9147) from altitude categories between 250 to about 2000 m were extracted from official Austrian registries across 10 years (2008–2017). Altitude-associated differences in health determinants were derived from the Austrian Health Interview Survey (2014). Results: The age-standardized incidence and mortality rates of male colorectal cancer decreased by 24.0% and 44.2%, and that of female breast cancer by 6.5% and 26.2%, respectively, from the lowest to the highest altitude level. Higher physical activity levels and lower body mass index for both sexes living at higher altitudes were found. Conclusions: Living at a moderate altitude was associated with a reduced incidence and (more pronounced) mortality from colorectal and breast cancer. Our results suggest a complex interaction between specific climate conditions and lifestyle behaviours. These observations may, in certain cases, support decision making when changing residence.

Does living at moderate altitudes in Austria affect mortality rates of various causes? An ecological study

ObjectivesThe effects of altitude residence on ageing, longevity and mortality are poorly understood. While adaptations to chronic exposure to altitude may exert beneficial effects on cardiovascular risk factors and some...

Reversal of Pulmonary Hypertension in a Patient with Chronic Mountain Sickness after Relocation to Low Altitude

Long-term high altitude residence can be complicated by development of Chronic Mountain Sickness (CMS) characterised by excessive erythrocytosis and neurological symptoms. In some patients, CMS may be associated with various degrees of Pulmonary Hypertension (PH). There have been no reports on changes in the pulmonary circulation and Right Ventricular (RV) structure following translocation to low altitude of patients with CMS. Here the authors report a case of 56 years old female patient, resident of Sary Mogol (3,000 m, Kyrgyzstan), diagnosed of CMS on clinical and laboratory examination. Transthoracic echocardiography revealed slightly dilated Right ventricle and significantly enlarged Pulmonary Artery diameter was found. The patient undergone complete resolution of symptoms and alleviation of PH within three years of residence at low altitude. Thus, relocation to low altitude cures CMS and reverses PH.

Differences in the prevalence of physical activity and cardiovascular risk factors between people living at low (

Living at moderate altitude (up to about 2,000 m) was shown to be associated with distinct health benefits, including lower mortality from cardiovascular diseases and certain cancers. However, it remains unclear, whether those benefits are mainly due to environmental conditions (e.g., hypoxia, temperature, solar ultra-violet radiation) or differences in lifestyle behavior, including regular physical activity levels. This study aims to compare altitude-related differences in levels of physical activity and the prevalence of cardiovascular risk factors such as obesity, hypertension, hypercholesterolemia, and diabetes in an Alpine country. We interrogated the Austrian Health Interview Survey (ATHIS) 2019, a nationally representative study of persons aged over 15 years living in private Austrian households. The results confirm a higher prevalence of hypertension (24.2% vs. 16.8%) in men living at low (<1,001 m) compared to those at moderate (1,001 to 2,000 m) altitude. Women living above 1,000 m tend to have a lower prevalence of hypercholesterolemia (14.8% vs. 18.8%) and diabetes (3.2% vs. 5.6%) than their lower living peers. Both sexes have lower average body mass index (BMI) when residing at moderate altitude (men: 25.7, women: 23.9) compared to those living lower (26.6 and 25.2). Severe obesity (BMI > 40) is almost exclusively restricted to low altitude dwellers. Only men report to be more physically active on average when living higher (1,453 vs. 1,113 weekly MET minutes). These novel findings confirm some distinct benefits of moderate altitude residence on heath. Beside climate conditions, differences in lifestyle behavior, i.e., physical activity, have to be considered when interpreting those health-related divergences, and consequently also mortality data, between people residing at low and moderate altitudes.

Residence at moderately high altitude and its relationship with WHO Group 1 pulmonary arterial hypertension symptom severity and clinical characteristics: the Pulmonary Hypertension Association Registry.

BackgroundWHO Group 1 pulmonary arterial hypertension is a progressive and potentially fatal disease. Individuals living at higher altitude are exposed to lower barometric pressure and hypobaric hypoxemia. This may result in pulmonary vasoconstriction and contribute to disease progression. We sought to examine the relationship between living at moderately high altitude and pulmonary arterial hypertension characteristics.MethodsForty-two US centers participating in the Pulmonary Hypertension Association Registry enrolled patients who met the definition of WHO Group 1 pulmonary arterial hypertension. We utilized baseline data and patient questionnaire responses. Patients were divided into two groups: moderately high altitude residence (home ≥4000 ft) and low altitude residence (home <4000 ft) based on zip-code. Clinical characteristics, hemodynamic data, patient demographics, and patient reported quality of life metrics were compared.ResultsControlling for potential confounders (age, sex at birth, body mass index, supplemental oxygen use, race, 100-day cigarette use, alcohol use, and pulmonary arterial hypertension medication use), subjects residing at moderately high altitude had a 6-min walk distance 32 m greater than those at low altitude, despite having a pulmonary vascular resistance that was 2.2 Wood units higher. Additionally, those residing at moderately high altitude had 3.7 times greater odds of using supplemental oxygen.ConclusionPatients with pulmonary arterial hypertension who live at moderately high altitude have a higher pulmonary vascular resistance and are more likely to need supplemental oxygen. Despite these findings, moderately high altitude Pulmonary Hypertension Association Registry patients have better functional tolerance as measured by 6-min walk distance. It is possible that a “high-altitude phenotype” of pulmonary arterial hypertension may exist. These findings warrant further study.

Pathways of factors exacerbating dental fluorosis risk at high altitude regions — A review

Many scientific reports emphasized that the extent of prevalence and severity of dental fluorosis is higher among the people residing at high altitude regions than lower altitudes, even though they are exposed to drinking water with similar or less fluoride levels. This review reports various factors which enhance the risk of prevalence and severity of dental fluorosis at high altitude regions through different pathways. Especially, this review focused on ecological, physiological, biochemical and dietary factors as well as to identify potential key areas to implement further research on control of dental fluorosis risk at high altitude regions. In addition, by considering the pathways of risks, suitable remedial measures are also recommended in this review to manage the dental fluorosis risk at higher altitude regions. • Acidosis due to chronic high altitude residence could enhance dental fluorosis. • High fluoride retention occurs due to impaired kidney function at higher altitude. • Need to maintain good nutrition status and intake of alkaline producing diets. • Optimum iodine and vitamin D intake helps to control dental fluorosis. • Need to keep the drinking water fluoride level < 0.1 mg/L at > 1500 m altitude.

Impact of residence altitude on readmission in patients with heart failure

ObjectiveMountain districts normally have tougher geographic conditions than plain districts, which might worsen heart failure (HF) conditions in patients. Also, those places frequently are associated with social problems of ageing,...

GW28-e0078 Altitude difference of Galectin-3 and Soluble ST2 levels in the patients with congestive heart failure and effects on ventricular remodeling

Nearly 100 million people live at altitudes greater than 2500m. Long-term high-altitude residents have lower ventilation and higher arterial Pco2,and in some cases, develop chronic medical problems attributable to their high -altitude residence. Heart failure patients face several physiologic

Sleep disordered breathing and acute mountain sickness in workers rapidly transported to the South Pole (2835 m)

BackgroundSleep disordered breathing may be a risk factor for high altitude illness. Past Antarctic sleep studies suggest that rapid transport from sea level (SL) to the Amundsen Scott South Pole Station (SP, 2835m) increases risk of Acute Mountain Sickness (AMS). We analyzed sleep studies in 38 healthy polar workers to explore the association between sleep disordered breathing and AMS after rapid transport to the South Pole. MethodsSubjects completed a baseline questionnaire, performed basic physiology tests, and were evaluated for AMS and medication use using an extended Lake Louise Questionnaire (LLQ) during their first week at the South Pole. Participants were included in this study if they took no medications and underwent polysomnography on their first nights at Sea Level and the South Pole using the Vivometrics LifeShirt®. Within group changes were assessed with Wilcoxon signed rank tests and between group differences were assessed with Kruskal–Wallis rank sum tests. ResultsOverall, 21/38 subjects met criteria for AMS at some time on or prior to the third morning at the South Pole. Subjective poor sleep quality was reported by both AMS (65%) and no AMS (41%) groups. The Apnea Hypopnea Index (AHI) increased significantly in both the AMS and no AMS groups, but the difference in the increase between the two groups was not statistically significant. Increased AHI was not associated with increased AMS symptoms. Previous altitude illness (p=0.06) and residence at low altitudes (p=0.02) were risk factors for AMS. ConclusionAMS was not significantly associated with sleep architecture changes or increased AHI. However, AHI sharply increased at South Pole (19/38 participants) primarily due to central apneas. Those developing AMS were more likely to have experienced previous problems at altitude and reported living at lowland altitudes within the 3 months prior to rapid transport to the South Pole than those without AMS.

THE DEVELOPMENT OF SPORTS, RECREATION AND ADVENTURE TOURISM IN TOURIST-GEOGRAPHICAL REGIONS OF BOSNIA AND HERZEGOVINA

Sports, recreation and adventure tourism are activities that relax tourists and put them away from everyday stress situations, and it all takes place through swimming, hiking, relaxing in nature, altitude residence, paragliding, rock climbing, rafting, cycling tours, golf, tennis, aqua aerobics, volleyball, skiing, etc. Natural and anthropogenic tourist potentials which exist in the BiH tourism and geographic regions are suitable for the development of these specific forms of tourism. Sports events are unavoidable side effects in the development of these forms of tourism. Entertainment - recreational tourist regional offer, in a broader sense, includes an offer that is used to meet all other needs of tourists, participants and organizers of such events. Moreover, sports, recreation and adventure programs, which are implemented as an integral part of tourism offer of the tourist-geographical regions, are certainly renting and using various sports facilities and equipment, schools of various sports skills, sports games, tournaments and contests followed by sports-entertainment attractions, which certainly lead to job creation and employment of professional staff and young population structure. It is necessary to ensure available public space for a part of these activities, then equipped sports and recreational fields or recreational sports equipment and halls for other activities, which also makes room for employment in BiH regions in which it is wanted to develop these specific forms of tourism. The aim of this study is to determine the possibilities for development of sports, recreation and adventure tourism in BiH tourist-geographical regions followed by their diversity and classification with respect to which natural-geographical tourist attractions will be developed. The priorities and problems of their tourist valorisation will be determined, as well as the way they are promoted among both foreign and domestic tourists. In this study, noticable are the following touristgeographical methods: analysis, synthesis, causal methods, classification, tourist valorization, field research and mapping methods.

Chronic hypoxia increases arterial blood pressure and reduces adenosine and ATP induced vasodilatation in skeletal muscle in healthy humans.

To determine the role played by adenosine, ATP and chemoreflex activation on the regulation of vascular conductance in chronic hypoxia. The vascular conductance response to low and high doses of adenosine and ATP was assessed in ten healthy men. Vasodilators were infused into the femoral artery at sea level and then after 8-12 days of residence at 4559 m above sea level. At sea level, the infusions were carried out while the subjects breathed room air, acute hypoxia (FI O2 = 0.11) and hyperoxia (FI O2 = 1); and at altitude (FI O2 = 0.21 and 1). Skeletal muscle P2Y2 receptor protein expression was determined in muscle biopsies after 4 weeks at 3454 m by Western blot. At altitude, mean arterial blood pressure was 13% higher (91 ± 2 vs. 102 ± 3 mmHg, P < 0.05) than at sea level and was unaltered by hyperoxic breathing. Baseline leg vascular conductance was 25% lower at altitude than at sea level (P < 0.05). At altitude, the high doses of adenosine and ATP reduced mean arterial blood pressure by 9-12%, independently of FI O2 . The change in vascular conductance in response to ATP was lower at altitude than at sea level by 24 and 38%, during the low and high ATP doses respectively (P < 0.05), and by 22% during the infusion with high adenosine doses. Hyperoxic breathing did not modify the response to vasodilators at sea level or at altitude. P2Y2 receptor expression remained unchanged with altitude residence. Short-term residence at altitude increases arterial blood pressure and reduces the vasodilatory responses to adenosine and ATP.

Lower obesity rate during residence at high altitude among a military population with frequent migration: a quasi experimental model for investigating spatial causation.

We sought to evaluate whether residence at high altitude is associated with the development of obesity among those at increased risk of becoming obese. Obesity, a leading global health priority, is often refractory to care. A potentially novel intervention is hypoxia, which has demonstrated positive long-term metabolic effects in rats. Whether or not high altitude residence confers benefit in humans, however, remains unknown. Using a quasi-experimental, retrospective study design, we observed all outpatient medical encounters for overweight active component enlisted service members in the U.S. Army or Air Force from January 2006 to December 2012 who were stationed in the United States. We compared high altitude (>1.96 kilometers above sea level) duty assignment with low altitude (<0.98 kilometers). The outcome of interest was obesity related ICD-9 codes (278.00-01, V85.3x-V85.54) by Cox regression. We found service members had a lower hazard ratio (HR) of incident obesity diagnosis if stationed at high altitude as compared to low altitude (HR 0.59, 95% confidence interval [CI] 0.54–0.65; p<0.001). Using geographic distribution of obesity prevalence among civilians throughout the U.S. as a covariate (as measured by the Centers for Disease Control and Prevention and the REGARDS study) also predicted obesity onset among service members. In conclusion, high altitude residence predicts lower rates of new obesity diagnoses among overweight service members in the U.S. Army and Air Force. Future studies should assign exposure using randomization, clarify the mechanism(s) of this relationship, and assess the net balance of harms and benefits of high altitude on obesity prevention.

A systematic analysis of pneumatosis cystoids intestinalis

To increase the understanding, diagnosis and treatment of pneumatosis cystoides intestinalis (PCI) and to find the characteristics and potential cause of the disease in China. We report here one case of PCI in a 70-year-old male patient who received a variety of treatment methods. Then, we systematically searched the PCI eligible literature published from an available Chinese database from May 2002 to May 2012, including CBM, CBMDisc, CMCC, VIP, Wanfang, and CNKI. The key words were pneumatosis cystoides intestinalis, pneumatosis, pneumatosis intestinalis, pneumatosis coli and mucosal gas. The patients' information, histories, therapies, courses, and outcomes were reviewed. The study group consisted of 239 PCI cases (male:female = 2.4:1) from 77 reported incidents. The mean age was 45.3 ± 15.6 years, and the median illness course was 6 mo. One hundred and sixty patients (66.9%) were in high altitude areas. In addition, 43.5% (104/239) of the patients had potential PCI-related disease, and 16.3% had complications with intestinal obstruction and perforation. The most common symptom was abdominal pain (53.9%), followed by diarrhea (53.0%), distention (42.4%), nausea and vomiting (14.3%), bloody stool (12.9%), mucous stool (12.0%) and constipation (7.8%). Most multiple pneumocysts developed in the submucosa of the colon (69.9%). The efficacy of the treatments by combined modalities, surgery, endoscopic treatment, conservative approach, oxygen, and antibiotics were 100%, 100%, 100%, 93.3%, 68.3% and 26.3%, respectively. PCI can be safely managed by conservative treatments, presents more frequently in males, in the large bowel and submucosa, than in females, in the small intestine and subserosa. High altitude residence maybe associated with the PCI etiology.

Point: Counterpoint: Hypobaric hypoxia induces/does not induce different responses from normobaric hypoxia

Point: Counterpoint: Hypobaric hypoxia induces/does not induce different responses from normobaric hypoxia

Changing patterns of neuropsychological functioning in children living at high altitude above and below 4000 m: a report from the Bolivian Children Living at Altitude (BoCLA) study

The brain is highly sensitive to environmental hypoxia. Little is known, however, about the neuropsychological effects of high altitude residence in the developing brain. We recently described only minor changes in processing speed in native Bolivian children and adolescents living at approximately 3700 m. However, evidence for loss of cerebral autoregulation above this altitude (4000 m) suggests a potential threshold of hypoxia severity over which neuropsychological functioning may be compromised. We conducted physiological and neuropsychological assessments in 62 Bolivian children and adolescents living at La Paz (∼3700 m) and El Alto (∼4100 m) in order to address this issue. Groups were equivalent in terms of age, gender, social class, schooling, parental education and genetic admixture. Apart from percentage of hemoglobin saturated with oxygen in arterial blood (%SpO(2)), participants did not differ in their basal cardiac and cerebrovascular performance as explored by heart rate, mean arterial pressure, end-tidal carbon dioxide, and cerebral blood flow velocity at the basilar, anterior, middle and posterior cerebral arteries. A comprehensive neuropsychological assessment was administered, including tests of executive functions, attention, memory and psychomotor performance. Participants living at extreme altitude showed lower levels of performance in all executive tests (Cohen effect size = -0.91), whereas all other domains remained unaffected by altitude of residence. These results are compatible with earlier physiological evidence of a transitional zone for cerebral autoregulation at an altitude of 4000 m. We now show that above this threshold, the developing brain is apparently increasingly vulnerable to neuropsychological deficit.