Early in the pandemic, researchers were eager to learn more about the COVID-19 virus and how it takes shape in different communities. One area of particular interest for some of those researchers was the relationship between COVID-19 and high altitude, as altitude has been shown to impact other chronic diseases like COPD¹, lung cancer², and cardiovascular disease³. However, many of the early studies that were conducted resulted in nonspecific findings or trends in data that could be better explained by different variables than solely altitude. 

For example, one of the preliminary studies conducted in Colombia analyzed positive cases, deaths, and case fatality rates in 70 different municipalities ranging from 1 to 3180m above sea level. What these researchers found was that there was a negative correlation between altitude and COVID-19 case fatality rates⁴, meaning there were less COVID-19 deaths at higher altitude when compared to those at low altitude. One thing that is mentioned by the researchers is that population density plays an important role in the transmission of this virus⁴. The researchers concluded that this negative correlation seen between altitude and COVID-19 fatalities could be better explained by the differences in population in the varying locations⁴. 

Another early study conducted in 2020 looked at around 4 months of data in the U.S and around 2 months of data in Mexico and found that U.S. communities living at >2000m elevation had higher mortality rates than those at <1500m⁵. In Mexico, individuals <65 years old, the risk of death due to COVID-19 was 36% for those living at >2000m when compared to those living at <1500m⁵.

We discussed some of these findings with Dr. Isain Zapata, who is one of the authors of the article “Revisiting the COVID-19 fatality rate and altitude associated through a comprehensive analysis”. Which was a study conducted by a group of researchers at Rocky Vista University that further investigated the relationship between altitude and COVID-19 fatalities. Dr. Zapata said that some of their motivation to look further into this relationship was due to the lack of consistency in the conclusions formed by many of the studies conducted early in the pandemic. He hypothesized that there could be a few reasons for these inconsistencies, one being that there is a large discrepancy over what level of elevation is considered “high altitude” and another being that many of the studies published early on were specific to a certain location. Lastly, these studies were solely looking at data from the first few months of the pandemic, when COVID-19 infections were just beginning to take form. 

In their study, this group of researchers looked at COVID-19 fatality data from March 2020 to March 2021 in the mountain region of the western United States, including Montana, Idaho, Wyoming, Nevada, Utah, Colorado, Arizona, and New Mexico. Within each state, they looked at the data specific to each county and then subdivided them into census blocks⁶. Then determined the weighted average of the block’s altitude and adjusted for population density⁶. 

They found that in Colorado, Idaho, and Wyoming, communities living at higher altitude had lower COVID-19 fatality rates⁶. This trend was also observed when they performed a meta-analysis of all of the data from the U.S. Mountain region⁶. However, when looking at Arizona, Montana, Nevada, and Utah individually, there was not a significant relationship observed between high altitude and COVID-19 mortality⁶. One of the points discussed by the researchers is that in these states, the discrepancy may be based on the population density⁶. In Arizona and Nevada, the majority of the population in that state live at lower altitudes⁶. The researchers also discuss that the size of the state and the number of counties in each state may also play a role in these trends⁶. 

They also found that in Arizona, Colorado, Idaho, and Wyoming, areas with higher median incomes were associated with lower COVID-19 fatality rates⁶. 

The researchers observed that in New Mexico, there was a reverse altitude effect, in which, there was higher mortality rates at higher altitudes⁶. There was also a higher associated risk across the whole mountain region for the Native American population⁶. One observation that was pointed out in the discussion section of this article, is that New Mexico has one of the highest Native American populations⁶. In addition, Native Americans have been shown to have higher incidence of developing chronic diseases that are associated with worse COVID-19 fatality rates⁶. 

So, what does this all of this mean? Overall, in the U.S. western Mountain region, there were fewer Covid-19 deaths for communities living at higher altitude when compared to those living at lower altitude⁶. This same trend was observed when just looking at the data for Colorado⁶. 

Another point that was discussed by the researchers is that these implications can likely be explained by both protective physiologic changes that occur at altitude as well as demographic trends⁶. The demographic trend may be hypothesized to be a result of people who choose to live in areas of higher altitude as they are often seeking more active lifestyles. The results of this study leave room for more research to be conducted on how our bodies physiology changes in order to adapt to life at higher altitudes.  

1. Andreas Horner et al., “Altitude and COPD Prevalence: Analysis of the Prepocol-Platino-Bold-Epi-Scan Study,” Respiratory Research 18, no. 1 (August 23, 2017), https://doi.org/10.1186/s12931-017-0643-5.
2. Kamen P. Simeonov and Daniel S. Himmelstein, Lung Cancer Incidence Decreases with Elevation: Evidence for Oxygen as an Inhaled Carcinogen, November 12, 2014, https://doi.org/10.7287/peerj.preprints.587v2.
3. Martin Burtscher, “Effects of Living at Higher Altitudes on Mortality: A Narrative Review,” Aging and Disease, 2014, https://doi.org/10.14336/ad.2014.0500274.
4. Eder Cano-Pérez et al., “Negative Correlation between Altitude and Covid-19 Pandemic in Colombia: A Preliminary Report,” The American Journal of Tropical Medicine and Hygiene 103, no. 6 (December 2, 2020): 2347–49, https://doi.org/10.4269/ajtmh.20-1027.
5. Orison O. Woolcott and Richard N. Bergman, “Mortality Attributed to Covid-19 in High-Altitude Populations,” High Altitude Medicine &amp; Biology 21, no. 4 (December 1, 2020): 409–16, https://doi.org/10.1089/ham.2020.0098.
6. Carson Bridgman et al., “Revisiting the Covid-19 Fatality Rate and Altitude Association through a Comprehensive Analysis,” Scientific Reports 12, no. 1 (October 27, 2022), https://doi.org/10.1038/s41598-022-21787-z.