Are you aware that living at altitudes can affect your chance of suffering stroke? This intriguing question is at the heart of a new study published in the open-access journal Frontiers in Physiology.
The study, which includes data from more than 100,000 stroke patients in 17 years it is the first study to look at stroke-related hospitalizations as well as deaths among Ecuadorians living at four distinct levels. Surprisingly enough, the study revealed that stroke-related deaths and stroke risk is lower for those who live at higher altitudes. This protection is most effective between 2,000 and 3500m.
At the correct altitude
Stroke is the most frequent cause of disability and death across the world. The majority of strokes are caused by a blockage in blood vessels that carry blood to the brain. You may be familiar with the most well-known health and lifestyle factors that increase stroke risk, including smoking high blood pressure, smoking cigarettes high cholesterol, and lack of physical exercise. However, there is another undiscovered factor that can influence your risk of having a stroke the altitude.
People who live at higher elevations have developed the ability to adapt to lower oxygen levels. It isn’t clear what this can do to the risk of stroke. There is some evidence that low levels of oxygen can result in stroke risk in short-term circumstances but it’s not clear what the risk for those who live at high altitudes.
Researchers in Ecuador are in an exceptional position to study these phenomena, as the presence of the Ecuadorian mountains means that people in the country are located at a variety of altitudes.
Our primary objective was to create awareness about the issue that isn’t well understood. That is, over 160 million people live above 2,500m and there is little information about the epidemiological variations in the case of stroke at high altitudes. We wanted to contribute to the development of knowledge about this population that is often thought to be the same as the population living at sea level, and from an anthropological point of view we are quite different.”
Esteban Ortiz-Prado, Study Lead Author and Professor, Universidad de las Americas
Uncovering the mystery
The researchers examined hospital records from Ecuador between 2001 until 2017. They examined deaths and hospitalizations for strokes in people who live at four different elevations such as low altitude (under 1,500m), moderate altitude (1.500-2,500m) and high altitude (2,500-3,500m) and very high altitude (3.500-5,500m).
The results showed that those who lived at higher elevations (above 2,500 meters) tend to experience strokes later in life compared with those who lived at lower altitudes. Intriguingly, people who resided at higher altitudes were also less likely to be hospitalized or die of stroke. This effect of protection was more pronounced between 2,000 and 3,500 metres and less than 3500 metres.
So, why might people who live at high altitudes be protected against stroke? People who live at higher altitudes may have developed adaptations to low oxygen levels and are more likely to create new blood vessels to overcome the damage caused by stroke. They may also have a better brain vascular system which can aid them in making the most of oxygen and safeguard them against the worst effects of stroke.
While more research is needed to understand the causes of this phenomenon, the results could provide some relief for those who are at the top of the world.
Ortiz-Prado, E., et al. (2021) Stroke-related Death at Different Altitudes: a 17 Year National Population-Based Analysis from Ecuador. Frontiers in Physiology. doi.org/10.3389/fphys.2021.733928.
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