Acute Ischemic Stroke at High Altitudes in China: Early Onset and Severe Manifestations

Prevalence and Risk Factors of Ocular Demodex at Ultra-High Altitude and Sea Level: A Cross-Sectional Study of Shigatse and Shanghai

Purpose: Demodex infestation is a risk factor for several ocular surface diseases. However, the prevalence of ocular Demodex infection in the ultra-high altitude population is not clear. This study aimed to compare the prevalence and factors associated with Demodex in populations residing in ultra-high altitude region and sea level areas. Methods: Consecutive patients who visited Shigatse People's Hospital (> 4,000 m) and Shanghai Tongren Hospital (sea level) for eye complaints between January 2023 and January 2024 were included. Subjects were divided into ultra-high altitude and sea level groups. All subjects underwent eyelash epilation for ocular Demodex identification and counting. Demographic and lifestyle information was also collected. Results: A total of 517 subjects were eligible, including 255 subjects in the ultra-high-altitude group and 262 subjects in the sea level group. In the overall analysis, the prevalence of ocular Demodex infection was significantly different between the ultra-high-altitude and sea level groups (15.7% vs. 33.2%, P < 0.001). Multiple logistic regression showed that age, time spent outdoors, and makeup were associated with ocular Demodex infection in both groups. In addition, in the ultra-high-altitude group, people who wear sun hats outdoors were more likely to be infected with Demodex. Conclusion: The infection rate of ocular Demodex in the residents of ultra-high altitude area was significantly lower than that in the residents of sea level area, which may be related to lower ambient temperature, lower humidity, and higher solar radiation. Additionally, age, time spent outdoors, and makeup may be associated with ocular Demodex infection.

The Effect of High-Altitude Hypoxia on Neuropsychiatric Functions

Liu, Bo, Minlan Yuan, Mei Yang, Hongru Zhu, and Wei Zhang. The effect of high-altitude hypoxia on neuropsychiatric functions. High Alt Med Biol. 25:26-41, 2024. Background: In recent years, there has been a growing popularity in engaging in activities at high altitudes, such as hiking and work. However, these high-altitude environments pose risks of hypoxia, which can lead to various acute or chronic cerebral diseases. These conditions include common neurological diseases such as acute mountain sickness (AMS), high-altitude cerebral edema, and altitude-related cerebrovascular diseases, as well as psychiatric disorders such as anxiety, depression, and psychosis. However, reviews of altitude-related neuropsychiatric conditions and their potential mechanisms are rare. Methods: We conducted searches on PubMed and Google Scholar, exploring existing literature encompassing preclinical and clinical studies. Our aim was to summarize the prevalent neuropsychiatric diseases induced by altitude hypoxia, the potential pathophysiological mechanisms, as well as the available pharmacological and nonpharmacological strategies for prevention and intervention. Results: The development of altitude-related cerebral diseases may arise from various pathogenic processes, including neurovascular alterations associated with hypoxia, cytotoxic responses, activation of reactive oxygen species, and dysregulation of the expression of hypoxia inducible factor-1 and nuclear factor erythroid 2-related factor 2. Furthermore, the interplay between hypoxia-induced neurological and psychiatric changes is believed to play a role in the progression of brain damage. Conclusions: While there is some evidence pointing to pathophysiological changes in hypoxia-induced brain damage, the precise mechanisms responsible for neuropsychiatric alterations remain elusive. Currently, the range of prevention and intervention strategies available is primarily focused on addressing AMS, with a preference for prevention rather than treatment.

Emerging Stroke Risk Factors: A Focus on Infectious and Environmental Determinants

This review focuses on emerging risk factors for stroke, including air pollution and climate change, gut microbiota, high altitude, and systemic infection. Up to 14% of all stroke-associated mortality is attributed to air pollution and is more pronounced in developing countries. Fine particulate matter and other air pollutants contribute to an increased stroke risk, and this risk appears to increase with higher levels and duration of exposure. Short term air pollution exposure has also been reported to increase the stroke risk. The gut microbiota is a complex ecosystem of bacteria and other microorganisms that reside in the digestive system and affect multiple body systems. Disruptions in the gut microbiota may contribute to stroke development, possibly by promoting inflammation and atherosclerosis. High altitudes have been associated with erythrocytosis and cerebrovascular sinus thrombosis, but several studies have reported an increased risk of thrombosis and ischemic stroke at high altitudes, typically above 3000 m. Systemic infection, particularly infections caused by viruses and bacteria, can also increase the risk of stroke. The risk seems to be greatest in the days to weeks following the infection, and the pathophysiology is complex. All these emerging risk factors are modifiable, and interventions to address them could potentially reduce stroke incidence.

Intra-arterial microguidewire electrocoagulation to treat intracranial vascular diseases

OBJECTIVE

To investigate the therapeutic effect of intra-arterial microguidewire electrocoagulation on intracranial vascular diseases.

METHODS

Data from 10 patients with cerebral aneurysms between May 2018 and September 2022 were analysed. Patients were treated with endovascular coil embolisation and microguidewire electrocoagulation. XperCT scans were conducted to identify new intracranial haemorrhage, infarction and hydrocephalus. Follow-up examinations were conducted 1, 3, 6 and 12 months after discharge.

RESULTS

After the patients received electrocoagulation for different durations, Raymond Grade 1 embolisation was achieved in all 10 patients. No complications, such as haemorrhage, infarction or hydrocephalus, were found during or after surgery. Ten patients were followed up for 6-12 months, and none had any symptoms or new neurological dysfunction 1 month after their operation. Among them, nine were followed up for 12 months, and digital subtraction angiography showed no recurrence of aneurysms or occlusion of parent arteries.

CONCLUSION

Intra-arterial microguidewire electrocoagulation can be used as a supplementary treatment for cerebral aneurysms. In cases of incomplete lesion embolisation and cases where tamponade treatment cannot continue, immediate thrombosis may occur. Thus, intra-arterial microguidewire electrocoagulation can help achieve patients' treatment goals.

Current status and quality of radiomics studies for predicting outcome in acute ischemic stroke patients: a systematic review and meta-analysis

Background

Pre-treatment prediction of reperfusion and long-term prognosis in acute ischemic stroke (AIS) patients is crucial for effective treatment and decision-making. Recent studies have demonstrated that the inclusion of radiomics data can improve the performance of predictive models. This paper reviews published studies focused on radiomics-based prediction of reperfusion and long-term prognosis in AIS patients.

Methods

We systematically searched PubMed, Web of Science, and Cochrane databases up to September 9, 2023, for studies on radiomics-based prediction of AIS patient outcomes. The methodological quality of the included studies was evaluated using the phase classification criteria, the radiomics quality scoring (RQS) tool, and the Prediction model Risk Of Bias Assessment Tool (PROBAST). Two separate meta-analyses were performed of these studies that predict long-term prognosis and reperfusion in AIS patients.

Results

Sixteen studies with sample sizes ranging from 67 to 3,001 were identified. Ten studies were classified as phase II, and the remaining were categorized as phase 0 (n = 2), phase I (n = 1), and phase III (n = 3). The mean RQS score of all studies was 39.41%, ranging from 5.56 to 75%. Most studies (87.5%, 14/16) were at high risk of bias due to their retrospective design. The remaining two studies were categorized as low risk and unclear risk, respectively. The pooled area under the curve (AUC) was 0.88 [95% confidence interval (CI) 0.84-0.92] for predicting the long-term prognosis and 0.80 (95% CI 0.74-0.86) for predicting reperfusion in AIS.

Conclusion

Radiomics has the potential to predict immediate reperfusion and long-term outcomes in AIS patients. Further external validation and evaluation within the clinical workflow can facilitate personalized treatment for AIS patients. This systematic review provides valuable insights for optimizing radiomics prediction systems for both reperfusion and long-term outcomes in AIS patients.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42023461671, identifier CRD42023461671.

Thromboelastographic and Gene Polymorphism Bimodality Detection for Dual Antiplatelet Aggregation Therapy in Individuals with Clopidogrel-resistant Symptomatic Intracranial Artery Stenosis

BACKGROUND

Recent research indicates that clopidogrel resistance is connected with a patient's future ischemia risk, hence increasing the likelihood of recurrent ischemic cerebrovascular disease. Thromboelastographic and clopidogrel gene polymorphism testing can be used to see how a person responds to antiplatelet therapy and change the treatment plan accordingly. This may be a good way to make antiplatelet aggregation therapy more effective and safer.

OBJECTIVE

The objective of this study was to investigate the efficacy of dual antiplatelet aggregation therapy in patients with symptomatic intracranial large artery stenosis being resistant to clopidogrel tablets. The thromboelastographic and gene polymorphism bimodality detection techniques were used to analyze the clopidogrel resistance influencing factors.

METHODS

89 patients with symptomatic intracranial large arterial stenosis who were admitted to our hospital from February 2021 to February 2022 were selected, classified as large artery atherosclerotic type by TOAST, and confirmed as having severe intracranial large arterial stenosis (70 % to 99 %) by magnetic resonance angiography (MRA), computed tomographic angiography (CTA), and digital subtraction angiography (DSA). All patients were treated with dual antiplatelet therapy with aspirin and clopidogrel, and thromboelastography and clopidogrel gene polymorphism were monitored 1 week later.

RESULTS

44 of 89 patients were clopidogrel-resistant. Among 44 patients, 20 were ticagrelorresistant and 24 were cilostazol-resistant. Clopidogrel had a resistance rate of 49.4%. The recurrence of ischemic cerebrovascular disease in the three groups was statistically significant (P<0.05) after 3 months of follow-up treatment, but bleeding (intracranial, gastrointestinal, respiratory, urinary, and mucocutaneous) and dyspnea were not. The clopidogrel-resistant group had a higher number of females, as well as higher levels of hypertension, diabetes, and platelet count than the sensitive group (P<0.05), but there was no significant difference in age, smoking, alcohol consumption, previous stroke, glycosylated haemoglobin, creatinine, or low-density cholesterol.

CONCLUSION

Using thromboelastographic and gene polymorphism bimodality detection, we found switching to ticagrelor antiplatelet aggregation therapy as better than switching to cilostazol in patients with symptomatic intracranial large artery stenosis being resistant to clopidogrel tablets. The results may be biased due to the study being a single-centre study and having a limited sample size.

Health status of the population in Naqu, Tibet and its latent class analysis: a cross-sectional survey

Background

Through a survey and analysis of the population's present state of health, it is possible to give data support for improving the health status of inhabitants in Naqu, Tibet. Additionally, it is possible to provide specific recommendations for the development of medical and healthcare facilities in Tibet.

Methods

The health scores of the participants were based on their responses to the four main sections of the questionnaire: dietary habits, living habits, health knowledge, and clinical disease history, and the variability of health status among groups with different characteristics was analyzed based on the scores. The four major sections were used to create classes of participants using latent class analysis (LCA). Using logistic regression, the factors influencing the classification of latent classes of health status were investigated.

Results

A total of 995 residents from 10 counties in Naqu were selected as the study subjects. And their demographic characteristics were described. The mean health score of residents after standardization was 81.59 ± 4.68. With the exception of gender, health scores differed between groups by age, education level, different occupations, marital status, and monthly income. The health status in Naqu, Tibet, was divided into two groups (entropy = 0.29, BLRT = 0.001, LMRT = 0.001) defined as the "good health group" and the "general health group." A monthly income of more than ¥5000 adverse to good health in Naqu, Tibet.

Discussion

Single, well-educated young adults in Naqu, Tibet, have outstanding health. The vast majority of people in Tibet's Naqu region were in good health. Furthermore, the population's latent health status was divided into two classes, each with good dietary and living habits choices, low health knowledge, and a history of several clinical diseases. Univariate and multivariate logistic regression analysis showed that monthly income more than ¥5000 was an independent risk factor for poor health status.

Prevalence and risk factors of stroke in high-altitude areas: a systematic review and meta-analysis

OBJECTIVE

The primary objective of this study is to investigate the prevalence and risk factors of stroke in high-altitude areas through a comprehensive systematic review and meta-analysis.

DESIGN

This study adopts a systematic review and meta-analysis design.

DATA SOURCES

A thorough search was conducted on databases including PubMed, Web of Science, Embase, Cochrane Library, MEDLINE and SCOPUS, covering the period up to June 2023.

ELIGIBILITY CRITERIA

Studies reporting the prevalence of stroke in high-altitude areas and exploring related risk factors were included, regardless of whether they involved clinical samples or the general population. Studies with incomplete, outdated or duplicate data were excluded.

DATA EXTRACTION AND SYNTHESIS

We performed eligibility screening, data extraction and quality evaluation of the retrieved articles. Meta-analysis was employed to estimate the prevalence and risk factors of stroke in high-altitude areas. The Newcastle-Ottawa Scale was used to assess the risk of bias.

RESULTS

A total of 17 studies encompassing 8 566 042 participants from four continents were included, with altitudes ranging from 1500 m to nearly 5000 m. The pooled prevalence of stroke in high-altitude areas was found to be 0.5% (95% CI 0.3%-7%). Notably, the prevalence was higher in clinical samples (1.2%; 0.4%-2.5%) compared with the general population (0.3%; 95% CI 0.1%-0.6%). When considering geographic regions, the aggregated data indicated that stroke prevalence in the Eurasia plate was 0.3% (0.2%-0.4%), while in the American region, it was 0.8% (0.4%-1.3%). Age (OR, 14.891), gender (OR, 1.289), hypertension (OR, 3.158) and obesity (OR, 1.502) were identified as significant risk factors for stroke in high-altitude areas.

CONCLUSIONS

The findings of this study provide insights into the pooled prevalence of stroke in high-altitude areas, highlighting variations based on geographic regions and sampling type. Moreover, age, gender, hypertension and obesity were found to be associated with the occurrence of stroke.

PROSPERO REGISTRATION NUMBER

CRD42022381541.

Predicting transient ischemic attack risk in patients with mild carotid stenosis using machine learning and CT radiomics

Objective

This study aims to establish a radiomics-based machine learning model that predicts the risk of transient ischemic attack in patients with mild carotid stenosis (30-50% North American Symptomatic Carotid Endarterectomy Trial) using extracted computed tomography radiomics features and clinical information.

Methods

A total of 179 patients underwent carotid computed tomography angiography (CTA), and 219 carotid arteries with a plaque at the carotid bifurcation or proximal to the internal carotid artery were selected. The patients were divided into two groups; patients with symptoms of transient ischemic attack after CTA and patients without symptoms of transient ischemic attack after CTA. Then we performed random sampling methods stratified by the predictive outcome to obtain the training set (N = 165) and testing set (N = 66). 3D Slicer was employed to select the site of plaque on the computed tomography image as the volume of interest. An open-source package PyRadiomics in Python was used to extract radiomics features from the volume of interests. The random forest and logistic regression models were used to screen feature variables, and five classification algorithms were used, including random forest, eXtreme Gradient Boosting, logistic regression, support vector machine, and k-nearest neighbors. Data on radiomic feature information, clinical information, and the combination of these pieces of information were used to generate the model that predicts the risk of transient ischemic attack in patients with mild carotid artery stenosis (30-50% North American Symptomatic Carotid Endarterectomy Trial).

Results

The random forest model that was built based on the radiomics and clinical feature information had the highest accuracy (area under curve = 0.879; 95% confidence interval, 0.787-0.979). The combined model outperformed the clinical model, whereas the combined model showed no significant difference from the radiomics model.

Conclusion

The random forest model constructed with both radiomics and clinical information can accurately predict and improve discriminative power of computed tomography angiography in identifying ischemic symptoms in patients with carotid atherosclerosis. This model can aid in guiding the follow-up treatment of patients at high risk.

The association between altitude and serum folate levels in Tibetan adults on the Tibetan plateau

This study investigated the relationship between residence altitude and serum folate levels in healthy Tibetans living on the Tibetan Plateau. Participants were selected from those who underwent physical examinations at our health center between November 2019 and February 2020. Demographic characteristics and medical histories were collected, and fasting blood was tested for serum folate and other hematological indicators. The relationship between altitude and serum folate levels was analyzed using a multivariable linear regression model. Serum folate levels were associated with altitude (β = - 0.44; 95% confidence interval [CI] - 0.71; - 0.16), hemoglobin (β = - 0.01; 95% CI - 0.03; - 0.00), red blood cells (β = - 0.72; 95% CI - 1.18; - 0.27), hematocrit (β = - 0.07; 95% CI - 0.12; - 0.02), high-density lipoprotein cholesterol (β = 2.67; 95% CI 1.35; 3.98), and sex (β = 0.68; 95% CI 0.12; 1.23). Multivariate linear regression analysis revealed that altitude was negatively associated with serum folate levels. After adjusting for confounding factors, serum folate levels decreased by 0.33 ng/mL per each 500-m increase in altitude (β = - 0.33; 95% CI - 0.6; - 0.05; P = 0.022). Altitude was negatively associated with serum folate levels in Tibetan adults. The relationship between altitude and folate levels should be further explored in populations of different races and disease states. Further large-scale prospective studies should illustrate the causality of this relationship.

Association of dietary pattern and Tibetan featured foods with high-altitude polycythemia in Naqu, Tibet: A 1:2 individual-matched case-control study

This study focused on the association of dietary patterns and Tibetan featured foods with high-altitude polycythemia (HAPC) in Naqu, Tibet, to explore the risk factors of HAPC in Naqu, Tibet, to raise awareness of the disease among the population and provide evidence for the development of prevention and treatment interventions. A 1:2 individual-matched case-control study design was used to select residents of three villages in the Naqu region of Tibet as the study population. During the health examination and questionnaire survey conducted from December 2020 to December 2021, a sample of 1,171 cases was collected. And after inclusion and exclusion criteria and energy intake correction, 100 patients diagnosed with HAPC using the “Qinghai criteria” were identified as the case group, while 1,059 patients without HAPC or HAPC -related diseases were identified as the control group. Individuals were matched by a 1:2 propensity score matching according to gender, age, body mass index (BMI), length of residence, working altitude, smoking status, and alcohol status. Dietary patterns were determined by a principal component analysis, and the scores of study subjects for each dietary pattern were calculated. The effect of dietary pattern scores and mean daily intake (g/day) of foods in the Tibetan specialty diet on the prevalence of HAPC was analyzed using conditional logistic regression. After propensity score matching, we found three main dietary patterns among residents in Naqu through principal component analysis, which were a “high protein pattern,” “snack food pattern,” and “vegetarian food pattern.” All three dietary patterns showed a high linear association with HAPC (p < 0.05) and were risk factors for HAPC. In the analysis of the relationship between Tibetan featured foods and the prevalence of HAPC, the results of the multifactorial analysis following adjustment for other featured foods showed that there was a positive correlation between the average daily intake of tsampa and the presence of HAPC, which was a risk factor. Additionally, there was an inverse correlation between the average daily intake of ghee tea and the presence of HAPC, which was a protective factor.

Correlation of acetyl-coenzyme A carboxylase 1 with Th17 and Th1 cells, serving as a potential prognostic biomarker for acute ischemic stroke patients

Background

Acetyl‐coenzyme A carboxylase 1 (ACC1) regulates lipid homeostasis, T helper (Th) cell differentiation, oxidative stress, inflammation response, and neurological process, engaging in acute ischemic stroke (AIS) pathogenesis, while its clinical utility in AIS is unclear. Hence, this study intended to explore the correlation among blood ACC1, Th17, and Th1 cells, and ACC1’s potency as a prognostic biomarker for AIS management.

Methods

ACC1 in peripheral blood mononuclear cells (PBMCs) of 160 AIS patients and 30 controls were determined using RT‐qPCR; blood Th17 and Th1 cells in AIS patients were quantified by flow cytometry.

Results

ACC1 was increased in AIS patients compared with controls (median (interquartile range): 2.540 (1.753–3.548) vs. 0.980 (0.655–1.743), p < 0.001), which exhibited a good value to reflect AIS risk with the area under the curve of 0.872 (95% CI: 0.805–0.939). Moreover, ACC1 was positively linked with Th17 (r = 0.374, p < 0.001) and Th1 (r = 0.178, p = 0.024) cells in AIS patients. Additionally, ACC1 (r = 0.328, p < 0.001), Th17 (r = 0.272, p = 0.001), and Th1 cells (r = 0.195, p = 0.014) were positively associated with the National Institutes of Health Stroke Scale score in AIS patients. ACC1 high vs. low (p = 0.038) and Th17 high vs. low (p = 0.026) were related to shortened recurrence‐free survival (RFS) in AIS patients, while Th1 cells (p = 0.179) were not correlated with RFS. Whereas ACC1 (p = 0.248), Th17 (p = 0.079), and Th1 cells (p = 0.130) were not linked with overall survival (OS) in AIS patients.

Conclusion

Circulating ACC1 overexpression correlates with increased Th17, Th1 cells, NIHSS score, and shortened RFS in AIS patients.

Chronic high-altitude exposure and the epidemiology of ischaemic stroke: a systematic review

INTRODUCTION

About 5.7% of the world population resides above 1500 m. It has been hypothesised that acute exposure to high-altitude locations can increase stroke risk, while chronic hypoxia can reduce stroke-related mortality.

OBJECTIVE

This review aims to provide an overview of the available evidence on the association between long-term high-altitude exposure and ischaemic stroke.

DESIGN

A systematic review was performed from 1 January 1960 to 1 December 2021 to assess the possible link between high-altitude exposure and ischaemic stroke. The AMED, EMBASE, Cochrane Library, PubMed, MEDLINE, the Europe PubMed Central and the Latin-American bibliographic database Scielo were accessed using the University of Southampton library tool Delphis. In this review, we included population and individual-based observational studies, including cross-sectional and longitudinal studies except for those merely descriptive individual-based case reports. Studies were limited to humans living or visiting high-altitude locations for at least 28 days as a cut-off point for chronic exposure.

RESULTS

We reviewed a total of 1890 abstracts retrieved during the first step of the literature review process. The authors acquired in full text as potentially relevant 204 studies. Only 17 documents met the inclusion criteria and were finally included. Ten studies clearly suggest that living at high altitudes may be associated with an increased risk of stroke; however, five studies suggest that altitude may act as a protective factor for the development of stroke, while two studies report ambiguous results.

CONCLUSIONS

This review suggests that the most robust studies are more likely to find that prolonged living at higher altitudes reduces the risk of developing stroke or dying from it. Increased irrigation due to angiogenesis and increased vascular perfusion might be the reason behind improved survival profiles among those living within this altitude range. In contrast, residing above 3500 m seems to be associated with an apparent increased risk of developing stroke, probably linked to the presence of polycythaemia and other associated factors such as increased blood viscosity.

Anterior Circulation Acute Ischemic Stroke in the Plateau of China: Risk Factors and Clinical Characteristics

Background and Purpose

Acute ischemic stroke has a high incidence in the plateau of China. It has unique characteristics compared to the plains, and the specific relationship with altitude has not yet been appreciated. This study aimed to investigate the specificity of the plateau's anterior circulation acute ischemic stroke in China.

Methods

To retrospectively collect clinical data of patients with first-episode acute ischemic stroke in the anterior circulation in Tianjin and Xining city. The differences in clinical presentation, laboratory, and imaging examinations were compared.

Results

Patients at high altitudes showed a significant trend toward lower age (61.0 ± 10.2 vs. 64.8 ± 8.1, P = 0.010) and had a history of dyslipidemia, higher levels of inflammatory markers, erythrocytosis, and alcohol abuse. The main manifestations were higher diastolic blood pressure (85.5 ± 14.0 mmHg vs. 76.8 ± 11.6 mmHg, P < 0.001), triglycerides [2.0 (1.8) mmol/L vs. 1.3 (0.9) mmol/L, P < 0.001], CRP [4.7 (4.4) mg/L vs. 2.1 (1.9) mg/L, P < 0.001], homocysteine levels [14.5 (11.7) μmol/L vs. 11.2 (5.2) μmol/L, P < 0.001]; larger infarct volume [3.5 (4.8) cm³ vs. 9.0 (6.9) cm³, P < 0.001] and worse prognosis. Patients at high altitudes had higher atherosclerotic indexes in cIMT and plaque than those in plains.

Conclusions

The natural habituation and genetic adaptation of people to the particular geo-climatic environment of the plateau have resulted in significant differences in disease characteristics. Patients with the anterior circulation acute ischemic stroke in the plateau show more unfavorable clinical manifestations and prognosis. This study provides a preliminary interpretation of the effects of altitude and suggests developing preventive and therapeutic protocol measures that are more appropriate for the plateau of China.

Recommendations for traveling to altitude with neurological disorders

BACKGROUND

Several neurological conditions might worsen with the exposure to high altitude (HA). The aim of this review was to summarize the available knowledge on the neurological HA illnesses and the risk for people with neurological disorders to attend HA locations.

METHODS

A search of literature was conducted for several neurological disorders in PubMed and other databases since 1970. The neurological conditions searched were migraine, different cerebrovascular disease, intracranial space occupying mass, multiple sclerosis, peripheral neuropathies, neuromuscular disorders, epileptic seizures, delirium, dementia, and Parkinson's disease (PD).

RESULTS

Attempts were made to classify the risk posed by each condition and to provide recommendations regarding medical evaluation and advice for or against traveling to altitude. Individual cases should be advised after careful examination and risk evaluation performed either in an outpatient mountain medicine service or by a physician with knowledge of HA risks. Preliminary diagnostic methods and anticipation of neurological complications are needed.

CONCLUSIONS

Our recommendations suggest absolute contraindications to HA exposure for the following neurological conditions: (1) Unstable conditions-such as recent strokes, (2) Diabetic neuropathy, (3) Transient ischemic attack in the last month, (4) Brain tumors, and 5. Neuromuscular disorders with a decrease of forced vital capacity >60%. We consider the following relative contraindications where decision has to be made case by case: (1) Epilepsy based on recurrence of seizure and stabilization with the therapy, (2) PD (± obstructive sleep apnea syndrome-OSAS), (3) Mild Cognitive Impairment (± OSAS), and (4) Patent foramen ovale and migraine have to be considered risk factors for acute mountain sickness.

Stroke-Related Mortality at Different Altitudes: A 17-Year Nationwide Population-Based Analysis From Ecuador

Introduction: Worldwide, more than 5.7% of the population reside above 1,500 m of elevation. It has been hypothesized that acute short-term hypoxia exposure could increase the risk of developing a stroke. Studies assessing the effect of altitude on stroke have provided conflicting results, some analyses suggest that long-term chronic exposure could be associated with reduced mortality and lower stroke incidence rates.

Methods: An ecological analysis of all stroke hospital admissions, mortality rates, and disability-adjusted life years in Ecuador was performed from 2001 to 2017. The cases and population at risk were categorized in low (<1,500 m), moderate (1,500–2,500 m), high (2,500–3,500 m), and very high altitude (3,500–5,500 m) according to the place of residence. The derived crude and direct standardized age-sex adjusted mortality and hospital admission rates were calculated.

Results: A total of 38,201 deaths and 75,893 stroke-related hospital admissions were reported. High altitude populations (HAP) had lower stroke mortality in men [OR: 0.91 (0.88–0.95)] and women [OR: 0.83 (0.79–0.86)]. In addition, HAP had a significant lower risk of getting admitted to the hospital when compared with the low altitude group in men [OR: 0.55 (CI 95% 0.54–0.56)] and women [OR: 0.65 (CI 95% 0.64–0.66)].

Conclusion: This is the first epidemiological study that aims to elucidate the association between stroke and altitude using four different elevation ranges. Our findings suggest that living at higher elevations offers a reduction or the risk of dying due to stroke as well as a reduction in the probability of being admitted to the hospital. Nevertheless, this protective factor has a stronger effect between 2,000 and 3,500 m.