Early to say high altitude can protect against COVID-19: Study

Despite recent reports of lower COVID-19 incidence among high-altitude populations, current data is insufficient to conclude that high altitude could protect against contracting the Coronavirus, say researchers.

"The reported lower incidence of COVID-19 among high-altitude residents is quite intriguing, but epidemiological observations presented so far from high-altitude regions are preliminary," said study researchers Matiram Pun from the University of Calgary and Erik Swenson from the University of Washington in the US.

According to the study, published in the journal High Altitude Medicine & Biology, there is currently little evidence supporting benefit of genetic or nongenomic adaptation to high-altitude hypoxia.

Environmental factors such as pollution, ambient temperature, humidity, and seasonal weather patterns at different latitudes may influence how severe the pandemic is and the incidence of infection in any part of the world.

In addition, recent epidemiological data have been used to propose that altitude of residence may not only influence those environmental features considered key to lesser viral transmission but also susceptibility to more severe forms of COVID-19 through hypoxic-hypobaria driven genomic or nongenomic adaptations specific to high-altitude populations.

In this review, the research team critically examined currently available scientific and epidemiological data pertaining to COVID-19 transmission in the attempt to determine whether living at high altitude and associated adaptations to hypobaric hypoxia might be protective as recent publications have claimed.

The researchers found that it is possible that early lockdown measures, media coverage, and preventive guidelines may have favourably worked in slowing the spread of the virus among high-altitude residents because the virus appeared later in mountainous regions.

Low population density, low traffic, or travel avoidance (from low-altitude population centres to high-altitude communities), and remoteness may have worked in tandem to further protect high-altitude residents.

It is also likely to take many days in some mountainous regions of developing countries to reach destinations, which may have provided sufficient isolation time in some cases.

However, cases of COVID-19 identified in the Qinghai-Tibet high-altitude plateau were related to contact with persons who had travelled from the Wuhan, the epicentre of COVID-19.

Aggressive implementation of preventive measures that target social isolation has helped to nullify sustained local transmission in Qinghai-Tibet high-altitude region, the team said.

Therefore, it might be easier to prevent community transmission at high altitude with travel restriction alone.

"The data regarding virus transmission should be carefully interpreted and any current observations regarding high altitude-related differences in incidence, prevalence, and morbidity/mortality of COVID-19 must be considered speculative," the authors wrote.

"We should avoid reaching the conclusion that any community has innate protection from COVID-19 in the absence of robust evidence," they concluded.