AUTHOR=Ortiz-Prado Esteban , Espinosa Patricio S. , Borrero Alfredo , Cordovez Simone P. , Vasconez Jorge E. , Barreto-Grimales Alejandra , Coral-Almeida Marco , Henriquez-Trujillo Aquiles R. , Simbaña-Rivera Katherine , Gomez-Barreno Lenin , Viscor Gines , Roderick Paul 

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

JOURNAL=Frontiers in Physiology

VOLUME=Volume 12 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2021.733928

DOI=10.3389/fphys.2021.733928

ISSN=1664-042X

ABSTRACT=Introduction:
Worldwide, more than 5.7% of the population reside above 1,500m 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 2001-2017. The cases and population at risk were categorized in low (<1,500m), moderate (1,500m -2,500m), high (2,500m -3,500m) and very high altitude (3,500-5,500m) 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 [CI95% 0.54 - 0.56]) and women (OR: 0.65 [CI95% [0.64 - 0.66]).  
Conclusions: 
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 2,000m to 3,500 m.