Mortality Attributed to COVID-19 in High-Altitude Populations

Woolcott, Orison O; Bergman, Richard N

Background: Since partial oxygen pressure decreases as altitude increases, environmental hypoxia could worsen COVID-19 patient's hypoxemia. We compared COVID-19 mortality at different altitudes. Methods: Retrospective analysis of population-level data on COVID-19 deaths in the U.S. (1,016 counties) and Mexico (567 municipalities). Mixed-model Poisson regression analysis of the association between altitude and COVID-19 mortality using individual-level data from 40,168 Mexican subjects with COVID-19, adjusting for multiple covariates. Results: Between January 20 and April 13, 2020, mortality rates were higher in U.S. counties located at [≥]2,000 m elevation vs. those located below 1,500 m (12.3 vs. 3.2 per 100,000; P<0.001). In Mexico, between March 13 and May 13, 2020, mortality rates were higher in municipalities located at [≥]2,000 m vs. <1,500 m (5.3 vs. 3.9 per 100,000; P<0.001). Among Mexican subjects <65 years old, the risk of death was 36% higher in those living at [≥]2,000 m vs. <1,500 m (adjusted incidence rate ratio: 1.36; 95% CI, 1.05-1.78; P=0.022). Among men, the risk of death was 31% higher at [≥]2,000 m vs. <1,500 m (adjusted IRR: 1.31; 95% CI, 1.03-1.66; P=0.025). No association was found among women. Conclusion: Altitude is associated with COVID-19 mortality in men younger than 65 years.