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Brain Sciences Dec 2022High-altitude (HA) exposure affects cognitive functions, but studies have found inconsistent results. The aim of this systematic review was to evaluate the effects of HA... (Review)
Review
High-altitude (HA) exposure affects cognitive functions, but studies have found inconsistent results. The aim of this systematic review was to evaluate the effects of HA exposure on cognitive functions in healthy subjects. A structural overview of the applied neuropsychological tests was provided with a classification of superordinate cognitive domains. A literature search was performed using PubMed up to October 2021 according to PRISMA guidelines. Eligibility criteria included a healthy human cohort exposed to altitude in the field (at minimum 2440 m [8000 ft]) or in a hypoxic environment in a laboratory, and an assessment of cognitive domains. The literature search identified 52 studies (29 of these were field studies; altitude range: 2440 m-8848 m [8000-29,029 ft]). Researchers applied 112 different neuropsychological tests. Attentional capacity, concentration, and executive functions were the most frequently studied. In the laboratory, the ratio of altitude-induced impairments (64.7%) was twice as high compared to results showing no change or improved results (35.3%), but altitudes studied were similar in the chamber compared to field studies. In the field, the opposite results were found (66.4 % no change or improvements, 33.6% impairments). Since better acclimatization can be assumed in the field studies, the findings support the hypothesis that sufficient acclimatization has beneficial effects on cognitive functions at HA. However, it also becomes apparent that research in this area would benefit most if a consensus could be reached on a standardized framework of freely available neurocognitive tests.
PubMed: 36552195
DOI: 10.3390/brainsci12121736 -
ERJ Open Research Apr 2016We used meta-analysis to measure the effect of high-altitude climate therapy (HACT) on lung function outcomes in asthma, and systematically searched PubMed, Embase and... (Review)
Review
We used meta-analysis to measure the effect of high-altitude climate therapy (HACT) on lung function outcomes in asthma, and systematically searched PubMed, Embase and www.elibrary.ru for publications appearing from 1970 to mid-2015. We included studies carried out with children or adults with an exposure of up to 12 weeks at an altitude of ≥1500 m above sea level. Changes in forced expiratory volume in 1 s (FEV), FEV/vital capacity ratio or peak expiratory flow rate as the HACT intervention outcomes were analysed. We included data for 907 participants (age range 4-58 years) from 21 studies, altogether including 28 substrata based on asthma type or severity. Only three of 21 included studies had high quality, whereas 93% of substudies reported lung function improvement with an overall pooled standardised mean difference (SMD) of 0.53 (95% CI 0.43-0.62). The measured effect of HACT was greater in adults (SMD 0.75, 95% CI 0.63-0.88, n=14) than in children (SMD 0.24, 95% CI 0.09-0.38, n=14). Studies at altitude >2000 m above sea level yielded the same effect as those at lower altitude. Based on a cut-point of a 0.50 change in SMD to define a meaningful clinical difference, HACT appears to have efficacy as an intervention. This extent of benefit appears to be limited to adults with asthma.
PubMed: 27730196
DOI: 10.1183/23120541.00097-2015 -
Hypertension Research : Official... Aug 2022This systematic review and meta-analysis synthesized the pooled prevalence of hypertension at high altitudes and explored its correlation with altitude using studies... (Meta-Analysis)
Meta-Analysis Review
This systematic review and meta-analysis synthesized the pooled prevalence of hypertension at high altitudes and explored its correlation with altitude using studies published in Chinese and English from database inception to February 2021. A systematic literature search was conducted among bibliographic databases (PubMed, Embase, and Web of Science) and three Chinese databases (CNKI, VIP, and Wanfang data) to identify eligible studies. A random-effects model was used to calculate the overall pooled prevalence of hypertension. The I statistic was used to assess heterogeneity across studies. Random-effects meta-regression was conducted to investigate covariates that may have influenced between-study heterogeneity. The pooled prevalence of hypertension among the general population in high-altitude areas was 33.0% (95% CI: 29.0-38.0%), with high between-study heterogeneity (I = 99.4%, P < 0.01). Subgroup analyses showed the pooled prevalence of hypertension in Tibetan individuals was significantly higher than that in non-Tibetan individuals living in the Himalayas and Pamir Mountains (41% vs. 18%). A trend toward an increase in the prevalence of hypertension was found with every 100-m increase in elevation (coefficient: 0.012, 95% CI: -0.001 to 0.025, P = 0.069) only in Tibetan individuals. In addition, in these individuals, we found an increase in mean diastolic BP with each 100-m increase in altitude (coefficient: 0.763, 95% CI: 0.122-1.403, P = 0.025). Our meta-analysis suggests that the pooled prevalence of hypertension among the general population in high-altitude areas is 33.0%. Subjects of Tibetan ethnicity were more prone to developing hypertension at high altitudes. However, a very weak relationship between altitude and the prevalence of hypertension was found only in Tibetan individuals.
Topics: Altitude; Blood Pressure; Frailty; Humans; Hypertension; Prevalence
PubMed: 35705740
DOI: 10.1038/s41440-022-00955-8 -
Current Environmental Health Reports Dec 2023Environmental exposures have been associated with increased risk of cardiovascular mortality and acute coronary events, but their relationship with out-of-hospital... (Review)
Review
PURPOSE OF REVIEW
Environmental exposures have been associated with increased risk of cardiovascular mortality and acute coronary events, but their relationship with out-of-hospital cardiac arrest (OHCA) and sudden cardiac death (SCD) remains unclear. SCD is an important contributor to the global burden of cardiovascular disease worldwide.
RECENT FINDINGS
Current literature suggests a relationship between environmental exposures and cardiovascular disease, but their relationship with OHCA/SCD remains unclear. A literature search was conducted in PubMed, Embase, Web of Science, and Global Health. Of 5138 studies identified by our literature search, this review included 30 studies on air pollution, 42 studies on temperature, 6 studies on both air pollution and temperature, and 1 study on altitude exposure and OHCA/SCD. Particulate matter air pollution, ozone, and both hot and cold temperatures are associated with increased risk of OHCA/SCD. Pollution and other exposures related to climate change play an important role in OHCA/SCD incidence.
Topics: Humans; Temperature; Cross-Over Studies; Air Pollution; Particulate Matter; Death, Sudden, Cardiac; Out-of-Hospital Cardiac Arrest; Environmental Exposure; Air Pollutants
PubMed: 37845484
DOI: 10.1007/s40572-023-00414-7 -
Journal of Global Infectious Diseases 2019Ecological factors are important indicators for tuberculosis (TB) notification. However, consolidation of evidence on the effect of altitude and temperature on TB...
BACKGROUND
Ecological factors are important indicators for tuberculosis (TB) notification. However, consolidation of evidence on the effect of altitude and temperature on TB notification rate has not yet been done. The aim of this review is to illustrate the effect of altitude and temperature on TB notification rate.
METHODS
Electronic searches were undertaken from PubMed, EMBASE, and Scopus databases. Hand searches of bibliographies of retrieved papers provided additional references. A review was performed using the Meta-analysis Of Observational Studies in Epidemiology guideline.
RESULTS
Nine articles from various geographic regions were included in the study. Five out of nine studies showed the effect of altitude and four articles identified temperature effects. Results showed that TB notification rates were lower at higher altitude and higher at a higher temperature.
CONCLUSION
This review provides qualitative evidence that TB notification rates increase with temperature and decrease with altitude. The findings of this review will encourage policymakers and program managers to consider seasonality and altitude differences in the design and implementation of TB prevention and control strategies.
PubMed: 31198309
DOI: 10.4103/jgid.jgid_95_18 -
International Journal of Gynaecology... May 2022To understand the relationship between birth weight and altitude to improve health outcomes in high-altitude populations, to systematically assess the impact of altitude... (Meta-Analysis)
Meta-Analysis Review
OBJECTIVE
To understand the relationship between birth weight and altitude to improve health outcomes in high-altitude populations, to systematically assess the impact of altitude on the likelihood of low birth weight (LBW), small for gestational age (SGA), and spontaneous preterm birth (sPTB), and to estimate the magnitude of reduced birth weight associated with altitude.
METHODS
PubMed, OvidEMBASE, Cochrane Library, Medline, Web of Science, and clinicaltrials.gov were searched (from inception to November 11, 2020). Observational, cohort, or case-control studies were included if they reported a high altitude (>2500 m) and appropriate control population.
RESULTS
Of 2524 studies identified, 59 were included (n = 1 604 770 pregnancies). Data were abstracted according to PRISMA guidelines, and were pooled using random-effects models. There are greater odds of LBW (odds ratio [OR] 1.47, 95% confidence interval [CI] 1.33-1.62, P < 0.001), SGA (OR 1.88, 95% CI 1.08-3.28, P = 0.026), and sPTB (OR 1.23, 95% CI 1.04-1.47, P = 0.016) in high- versus low-altitude pregnancies. Birth weight decreases by 54.7 g (±13.0 g, P < 0.0001) per 1000 m increase in altitude. Average gestational age at delivery was not significantly different.
CONCLUSION
Globally, the likelihood of adverse perinatal outcomes, including LBW, SGA, and sPTB, increases in high-altitude pregnancies. There is an inverse relationship between birth weight and altitude. These findings have important implications for the increasing global population living at altitudes above 2500 m.
Topics: Altitude; Birth Weight; Female; Fetal Development; Humans; Infant, Newborn; Infant, Small for Gestational Age; Pregnancy; Pregnancy Outcome; Premature Birth
PubMed: 34101174
DOI: 10.1002/ijgo.13779 -
The Medical Journal of Australia Apr 2017To review the literature on the comparative efficacy of psychological, behavioural and medical therapies for acrophobia (fear of heights). (Meta-Analysis)
Meta-Analysis Review
OBJECTIVE
To review the literature on the comparative efficacy of psychological, behavioural and medical therapies for acrophobia (fear of heights).
DATA SOURCES
Multiple databases were searched through the Cochrane Common Mental Disorders review group on 1 December 2015.
DATA SYNTHESIS
The data were extracted independently and were pooled using RevMan version 5.3.5. The main outcome measures were changes from baseline on questionnaires for measurement of fear of heights, such as the Acrophobia Questionnaire (AQ), Attitude Towards Height Questionnaire (ATHQ), and behavioural avoidance tests. Individual and pooled analyses were conducted. Sixteen studies were included. Analysis of pooled outcomes showed that desensitisation (DS) measured by the post-test AQ anxiety score (standardised mean difference [SMD], -1.24; 95% CI, -1.88 to -0.60) and in vivo exposure (IVE) were effective in the short term compared with control (SMD, -0.74; 95% CI, -1.22 to -0.25). IVE was not effective in the long term (SMD, -0.34; 95%CI -0.76 to 0.08) and there were no follow-up data for DS. Virtual reality exposure (VRE) therapy was effective when assessed with the ATHQ but not the AQ. Augmentation of VRE with medication was promising. The number needed to treat (NNT) ranged from 1.4 (95% CI, 1.0 to 2.2) for IVE therapy with oppositional actions (a psychological process) versus waitlist control to an NNT of 6.0 (95% CI, 2.8 to 35.5) for the rapid phobia cure (a neurolinguistic programming technique) versus a mindfulness exercise as the control activity. It was often unclear if there were biases in the included studies.
CONCLUSIONS AND RELEVANCE
A range of therapies are effective for acrophobia in the short term but not in the long term. Many of the comparative studies showed equivalence between therapies, but this finding may be due to a type II statistical error. The quality of reporting was poor in most studies.
Topics: Altitude; Comparative Effectiveness Research; Humans; Patient Outcome Assessment; Phobic Disorders; Psychotherapy; Space Perception; Visual Perception
PubMed: 28359010
DOI: 10.5694/mja16.00540 -
Frontiers in Public Health 2022Nature exposure is a widely accepted option for promoting public health owing to the recent surge of scientific evidence. However, the actual settings to facilitate this... (Meta-Analysis)
Meta-Analysis
INTRODUCTION
Nature exposure is a widely accepted option for promoting public health owing to the recent surge of scientific evidence. However, the actual settings to facilitate this initiative is yet to be extensively reviewed. In this systematic review, we have aimed to provide an up-to-date summary of interventional studies investigating the psycho-physiological effects of forests and urban forests, including details on their physical settings, and investigate an effect-modifying role of altitude and summarize data on the magnitude and shape of the association.
METHODS
A keyword search using five electronic academic databases (PubMed, Embase, PsycINFO, Web of Science, and Scopus) was conducted to identify relevant articles published in English from the inception year to the end of February 2022. The methodological quality was evaluated using the ROBINS-I or ROB2 tool, depending on the study design. Meta-regression and random effects model were jointly used to examine the relationship between altitude and health outcomes.
RESULTS
We included 27 eligible studies and 31 cases extracted from 19 studies were used for the meta-analysis. In the meta-regression, we observed a non-linear association between altitude and psycho-physiological effects. Altitude had a positive quadratic association with anxiety ( < 0.000, adjusted = 96.79%), depression ( < 0.000, adjusted = 98.78%), and fatigue ( < 0.000, adjusted = 64.74%) alleviating effects. Conversely, altitude demonstrated a negative non-linear association with the blood pressure-lowering effect ( = 0.009, adjusted = 32.83%). Additionally, the thermal index (THI) and illuminance (lx) levels were significantly associated with effect sizes of psychological restoration.
DISCUSSION
This review provides moderate-certainty evidence for an effect-modifying role of altitude. The meta-regression results suggested the optimal and minimal altitude ranges for psychological restoration and physiological relaxation, respectively. Despite some limitations, the study findings provide a significant basis for utilizing altitude, which is easily accessible and simple, to promote the health benefits of nature-based initiatives.
SYSTEMATIC REVIEW REGISTRATION
https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022310894, identifier: CRD42022310894.
Topics: Humans; Anxiety; Anxiety Disorders; Databases, Factual; Fatigue; Public Health
PubMed: 36504926
DOI: 10.3389/fpubh.2022.1021618 -
American Journal of Obstetrics &... Sep 2021Exposure to high altitude (≥2500 m) is associated with increased arterial blood pressure. During pregnancy, even a mild elevation of maternal blood pressure is... (Meta-Analysis)
Meta-Analysis Review
OBJECTIVE
Exposure to high altitude (≥2500 m) is associated with increased arterial blood pressure. During pregnancy, even a mild elevation of maternal blood pressure is associated with reduced birthweight and increased prevalence of pregnancy complications. This study aimed to systematically assess the impact of altitude on maternal blood pressure at term and on the prevalence of hypertensive disorders of pregnancy.
DATA SOURCES
PubMed, Ovid Embase, Cochrane Library, Medline, Web of Science, and ClinicalTrials.gov were searched (inception to November 11, 2020).
STUDY APPRAISAL AND SYNTHESIS METHODS
Observational, cohort, or case-control studies were included if they reported a high-altitude and appropriate control pregnant population. Studies published >50 years ago were excluded; 2 reviewers independently assessed articles for eligibility and risk of bias.
RESULTS
At high altitude, maternal systolic and diastolic blood pressure at term was higher than at low altitude (4.8±1.6 mm Hg; P<.001; 4.0±0.8 mm Hg; P<.001, respectively). Hypertensive disorders of pregnancy were more common at high altitude (odds ratio, 1.31 [1.03-1.65]; P<.05). The prevalence of gestational hypertension was nearly twice as high at high altitude (odds ratio, 1.92 [1.15-3.22]; P<.05) but the prevalence of preeclampsia was half as high (odds ratio, 0.57 [0.46-0.70]; P<.001). The likelihood of stillbirth was increased by 63% in pregnancies at high altitude compared with low altitude (odds ratio, 1.63 [1.12-2.35]; P<.01).
CONCLUSION
Maternal blood pressure is higher at term in pregnancies at high altitude than low altitude, accompanied with an increased risk of gestational hypertension but not preeclampsia. Risk of stillbirth at high altitude is also increased. With a growing population residing at high altitude worldwide, it is essential to clearly define the associated risk of adverse pregnancy outcomes.
Topics: Altitude; Blood Pressure; Female; Humans; Hypertension, Pregnancy-Induced; Pre-Eclampsia; Pregnancy; Pregnancy Outcome
PubMed: 34023533
DOI: 10.1016/j.ajogmf.2021.100400 -
Revue Neurologique Apr 2017High altitude may be a factor associated with cerebral venous thrombosis (CVT). As our knowledge of CVT at high altitude is limited, it was decided to pool such... (Review)
Review
BACKGROUND AND OBJECTIVE
High altitude may be a factor associated with cerebral venous thrombosis (CVT). As our knowledge of CVT at high altitude is limited, it was decided to pool such information from the available case studies to determine whether high altitude can predispose to CVT.
METHODS
A systematic review of the literature was performed for cases reporting CVT at high altitude. Searches of the PubMed database (up to July 2016) were performed for publications, using 'cerebral venous thrombosis' and 'high altitude' as keywords. Cross-referencing was also done to complete the search.
RESULTS
Ultimately, 13 articles were included in our systematic review. The population consisted of 17 patients, predominately male (14/17), with a mean age of 32 (range: 19-47) years. Altitude range was 3000-8200m. Nine patients stayed at high altitude for>2 weeks; the duration of high altitude stay was unknown for the remainder. A hypercoagulable state was found in nine patients: secondary polycythemia in five; protein C deficiency in one; protein S deficiency in one; and factor V Leiden mutations in two. No comorbidities were found in any of these patients.
CONCLUSION
Long-term stays at high altitude in association with a hypercoagulable state - in particular, congenital or acquired thrombophilia - appears to predispose to CVT. The association of CVT with a single exposure to high altitude seems low, but the risk cannot as yet be specifically estimated.
Topics: Adult; Altitude; Blood Coagulation Disorders; Female; Humans; Intracranial Thrombosis; Male; Middle Aged; Neuroimaging; Venous Thrombosis; Young Adult
PubMed: 28038774
DOI: 10.1016/j.neurol.2016.11.004