What is Altitude Sickness? - Definition & Causes

Instructor: Dominic Corsini
Sometimes people get dizzy when hiking in the mountains. Why does this happen? How can climbing make you ill? And, how high must someone go before this occurs? This lesson answers those questions by further investigating altitude sickness.

What is Altitude Sickness?

Have you ever been motivated to get outside during a bright sunny summer day? Now, suppose on such as occasion you feel motivated to go hiking in the mountains. You start your hike out feeling great. However, after a few miles you start getting lightheaded and develop a headache. Many people may attribute this to over-stress, undernourishment, or some other perceived malady. However, depending on where in the mountains you hiked, you may be suffering from altitude sickness. Altitude sickness is a condition that occurs when your body cannot get enough oxygen from the air. Oxygen is a highly reactive gas in the air that is vital for our survival. Needless to say, this isn't a good situation for someone to be in. Now, let's investigate the phenomena further by looking at what could cause altitude sickness.

Causes of Altitude Sickness

Typically, altitude sickness occurs at high altitudes, where the air is thinner. You see, the Earth's atmosphere becomes less dense as you increase in altitude. The atmosphere is the collection of gases that surrounds the Earth. This means that the amount of available oxygen decreases, while altitude increases. So the further you walk up a mountain, the less oxygen there is for your body.

Mountain Air Density
Mountain Air Density

Generally, people are safe from altitude sickness provided they stay below 8,000 feet. However, this is not a guaranteed number and many mountain summits exceed the 8,000-foot mark. Individual physiology will determine who is affected by altitude sickness and who is not. In fact, even today experts cannot accurately predict which individuals are most susceptible to altitude sickness.

Air Density
Air Density

The biological premise behind altitude sickness works like this; your blood contains millions of red blood cells. Red blood cells are responsible for carrying oxygen away from your lungs and towards your body tissues. When there is less oxygen available, the ability of your red blood cells to perform this function is compromised. This is what happens with altitude sickness, where your body is deprived of needed oxygen.

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