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Background: Hypoxia and old age impair postural control and may therefore enhance the risk of accidents. We investigated whether acetazolamide, the recommended drug for prevention of acute mountain sickness, may prevent altitude-induced deterioration of postural control in older persons. Methods: In this parallel-design trial, 95 healthy volunteers, 40 years of age or older, living <1,000 m, were randomized to preventive therapy with acetazolamide (375 mg/d) or placebo starting 24 h before and during a 2-day sojourn at 3,100 m. Instability of postural control was quantified by a balance platform with the center of pressure path length (COPL) as primary outcome while pulse oximetry (SpO2) was monitored. Effects of altitude and treatment on COPL were evaluated by ordered logistic regression. www.ClinicalTrials.gov NCT03536429. Results: In participants taking placebo, ascent from 760 m to 3,100 m increased median COPL from 25.8 cm to 27.6 cm (odds ratio 3.80, 95%CI 2.53-5.70) and decreased SpO2 from 96% to 91% (odds ratio 0.0003, 95%CI 0.0002-0.0007); in participants taking acetazolamide, altitude ascent increased COPL from 24.6 cm to 27.3 cm (odds ratio 2.22, 95%CI 1.57-3.13), while SpO2 decreased from 96% to 93% (odds ratio 0.007, 95%CI 0.004-0.012). Altitude-induced increases in COPL were smaller with acetazolamide vs. placebo (odds ratio 0.58, 95%CI 0.34-0.99) while drops in SpO2 were mitigated (odds ratio 19.2, 95%CI 9.9-37.6). Conclusion: In healthy individuals, 40 years of age or older, postural control was impaired after spending a night at 3,100 m. The altitude-induced deterioration of postural control was mitigated by acetazolamide, most likely due to the associated improvement in oxygenation.
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Background: Effects of prolonged and repeated high-altitude exposure on oxygenation and control of breathing remain uncertain. We hypothesized that prolonged and repeated high-altitude exposure will improve altitude-induced deoxygenation and breathing instability. Methods: 21 healthy lowlanders, aged 18-30y, underwent two 7-day sojourns at a high-altitude station in Chile (4-8 hrs/day at 5,050 m, nights at 2,900 m), separated by a 1-week recovery period at 520 m. Respiratory sleep studies recording mean nocturnal pulse oximetry (SpO2), oxygen desaturation index (ODI, >3% dips in SpO2), breathing patterns and subjective sleep quality by visual analog scale (SQ-VAS, 0-100% with increasing quality), were evaluated at 520 m and during nights 1 and 6 at 2,900 m in the 1st and 2nd altitude sojourn. Results: At 520 m, mean ± SD nocturnal SpO2 was 94 ± 1%, ODI 2.2 ± 1.2/h, SQ-VAS 59 ± 20%. Corresponding values at 2,900 m, 1st sojourn, night 1 were: SpO2 86 ± 2%, ODI 23.4 ± 22.8/h, SQ-VAS 39 ± 23%; 1st sojourn, night 6: SpO2 90 ± 1%, ODI 7.3 ± 4.4/h, SQ-VAS 55 ± 20% (p < 0.05, all differences within corresponding variables). Mean differences (Δ, 95%CI) in acute effects (2,900 m, night 1, vs 520 m) between 2nd vs 1st altitude sojourn were: ΔSpO2 0% (-1 to 1), ΔODI -9.2/h (-18.0 to -0.5), ΔSQ-VAS 10% (-6 to 27); differences in acclimatization (changes night 6 vs 1), between 2nd vs 1st sojourn at 2,900 m were: ΔSpO2 -1% (-2 to 0), ΔODI 11.1/h (2.5 to 19.7), ΔSQ-VAS -15% (-31 to 1). Conclusion: Acute high-altitude exposure induced nocturnal hypoxemia, cyclic deoxygenations and impaired sleep quality. Acclimatization mitigated these effects. After recovery at 520 m, repeated exposure diminished high-altitude-induced deoxygenation and breathing instability, suggesting some retention of adaptation induced by the first altitude sojourn while subjective sleep quality remained similarly impaired.
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Abstract Introduction: Incidence, case fatality, and mortality rates of COVID-19 are not the same in the different regions of Peru, a situation that may be related to factors that have been little studied, such as altitude. Likewise, environmental characteristics typical of altitude (atmospheric pressure, relative humidity, etc.) could explain the dynamics of COVID-19 transmission. Objective: To determine the correlation between altitude and COVID-19 incidence, case fatality, and mortality rates in Peru. Materials and methods: Multiple-group ecological study. A secondary analysis of official COVID-19 data from 1 874 districts of Peru reported until February 2021 was performed. The variable altitude was categorized as low (0-999 m.a.s.l.), medium (1 000-2 499 m.a.s.l.), and high (>2 500 m.a.s.l.). Cumulative incidence, case fatality, and mortality rates of COVID-19 were calculated as the number of cases among the total population of each district multiplied by 10 000, the number of deaths among the number of cases multiplied by 100, and the number of deaths among the total population of each district multiplied by 100 000, respectively. Bivariate (Spearman's rank correlation and Kruskal-Wallis test) and multivariate analyses (multiple linear regression) were used for data analysis, with a confidence level of 95%. Results: An inverse correlation between cumulative incidence rate (1 823 districts) and altitude (Rho: -0.355; p<0.001) was observed, i.e., it decreased at a higher altitude. In turn, there was a direct correlation between case fatality rate (1 526 districts) and altitude (Rho: 0.131; p<0.001), i.e., it increased at a higher altitude. Although mortality rate showed an inverse correlation with altitude (Rho: -0.310; p<0.000), it varied heterogeneously depending on altitude levels. In the multivariate analysis, after adjusting the model for poverty and population density, altitude was associated with incidence (p<0.001) and case fatality rates (p=0.009), but not with mortality rate (p=0.179). Conclusion: During the study period, an inverse correlation between altitude and COVID-19 cumulative incidence rate, as well as a direct correlation between altitude and case fatality rate, were observed in Peru.
Resumen Introducción. La incidencia, la letalidad y la mortalidad por COVID-19 no han sido iguales en las regiones del Perú, situación que puede estar relacionada con factores pocos estudiados como la altitud; asimismo, características ambientales propias de la altura (presión atmosférica, humedad relativa, etc.) podrían explicar la dinámica de transmisión de la COVID-19. Objetivo. Determinar la relación entre altitud e incidencia, letalidad y mortalidad por COVID-19 en Perú. Materiales y métodos. Estudio ecológico de grupos múltiples. Se realizó un análisis secundario de datos oficiales sobre COVID-19 de 1 874 distritos del Perú reportados hasta febrero de 2021. La variable altitud se categorizó como baja (0-999m s.n.m.), media (1 000-2 499m s.n.m.) y elevada (>2 500m s.n.m.). Las tasas de incidencia acumulada, letalidad y mortalidad por COVID-19 se calcularon como el número de casos entre la población total de cada distrito multiplicado por 10 000, el número de defunciones entre el número de casos multiplicado por 100 y el número de defunciones entre la población total de cada distrito multiplicado por 100 000, respectivamente. Para el análisis de los datos se empleó estadística bivariada (coeficiente de correlación de Spearman y prueba de Kruskal-Wallis) y multivariada (regresión lineal múltiple), con un nivel de confianza del 95%. Resultados. Se observó una correlación inversa entre la tasa de incidencia acumulada (1 823 distritos) y la altitud (Rho: -0.355; p<0.001), es decir, se redujo a mayor altitud, y una correlación directa entre la tasa de letalidad (1526 distritos) y la altitud (Rho: 0.131; p<0.001), es decir, aumentó a mayor altitud. Aunque la tasa de mortalidad mostró una correlación inversa con la altitud (Rho: -0.310; p<0.000), esta varía heterogéneamente según niveles altitudinales. En el análisis multivariado, luego de ajustar el modelo por pobreza y densidad poblacional, la altitud se asoció con las tasas de incidencia (p<0.001) y letalidad (p=0.009), pero no con la de mortalidad (p=0.179). Conclusión. Se observó una correlación inversa entre la altitud y la tasa de incidencia de COVID-19 y una correlación directa entre la altitud y la tasa de letalidad en Perú durante el periodo de estudio. No se encontró una correlación entre altitud y tasa de mortalidad.