Previous evidence suggests that living at higher altitudes leads to longer life spans for humans. Scientists at Harvard Medical School wanted to know why.
In a study released this week of mice, evidence found restricting oxygen flow led to significantly longer lifespans. Researchers placed mice into two chambers. One set of mice was in a chamber with normal oxygen levels; another set was in a section with an oxygen level equivalent to Mount Everest’s. The mice employed in the study generally have short life spans.
The group of mice with their oxygen restricted lived, on average, 24 weeks, compared to 16 weeks for those who experienced normal oxygen levels. Harvard Medical School also found the maximum lifespan for mice with oxygen restriction was about 30% longer.
The researchers also noted that oxygen-restricted mice preserved neurologic function longer.
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In 2011, the National Institutes of Health released data that found that men who live 1,500 meters above sea level live an average of 1.2 to 3.6 years longer than those who live within 100 meters of sea level. Women who live at high altitudes live an average of .5 to 2.5 years longer.
In the case of the humans I would have hypothesized it was cleaner air or some such thing leading to longer lives. But with the mouse experiments I don’t understand how this might work.
So would one of the side effects of smoking possibly be longer life?
Reduction of the body’s ability to process oxygen could suggest maybe, except for the increase in heart disease and cancer that seem to occur otherwise….
I need more information. The percentage of oxygen in the air at 30,000′ is approximately the same as the percentage at sea level.
Perhaps the issue is pressure per square inch.
Our bodies respond to the partial pressure of inspired oxygen, which is the product of the absolute pressure and the fraction of O2 (fo2). As you note, the fraction remains constant. However at 9,000m the standard atmosphere is .3080 bar, let’s call that .3 Atmospheres Absolute (vs 1 ATA at sea level). .3*.21 -> .063 partial pressure O2 (vs .21 PPO2 at sea level). This is a wildly and problematically low number, hence the summit of Everest being in the “death zone” and the requirement for supplemental oxygen (same for oxygen masks in airplanes when the cabin pressure altitude exceeds 15K feet).
So yes, the fraction O2 is the same, but the pressure exerted (and density / number of inspired molecules in a lungful of air) is substantially lower at higher elevation.
For Joe, the obvious presumption that I’m not claiming in any way to scientifically back up would be a reduction in oxidative stress at lower PO2.
A couple of things…. well, several:
I’d guess that metabolism slows and they are in a semi-hibernation mode.
Mice have a much smaller brain : body ratio, and that would likely have a significant impact on cognitive function. Given that roughly 20% of a human’s blood, and 25% of the O2, goes to the human brain, lowering oxy intake would be a serious problem, at least for most people.
Many people, not just elite athletes, use elevated oxygen to improve performance, but physically and mentally.
Hyperbaric chambers, with higher pressure and oxygen levels, can be used to treat a number of medical conditions, from TBI to “flesh-eating bacteria,” and I have no idea what the long-term disease outcomes from lower O2 levels would be WRT health.
“25% of the O2, goes to the human brain, lowering oxy intake would be a serious problem, at least for most people.”
Thanks Rolf! I needed a new excuse! Being dropped as a child wasn’t working so well.
Lower oxygen intake is a serious problem, yes indeed. Pilots and skydivers know this well. FAA rules require “supplemental oxygen” for pilots if they spend more than 30 minutes about 10k feet in an unpressurized aircraft, and oxygen for all occupants above 14k. (Give or take some details; I’m working from memory here.) The reason is cognitive impairment from reduced oxygen. I definitely remember it from the one jump I made from 15.5k or so in Hawaii, without O2. Not enough to be a danger, but enough to be observable when I thought to pay attention to the question.
Things get more interesting at much higher altitudes, from risk of “the bends” (nitrogen bubbles in the blood) to blood boiling at body temperature at around 50k or so (where a full pressure suit becomes mandatory).
Then again, some of these things one can adapt to over time, which is why athletes may spend a month or so in Leadville, CO, to increase their body’s ability to take in oxygen. That only gets you so far, though; I don’t think any amount of acclimation makes it safe to climb Everest without oxygen, though if memory serves it has been done, once or twice.
I hear if you restrict it enough, you quit aging altogether!
At my age I’m having a hard enough time with the 20.99% by volume I’m getting at present.
But it’s a worthy experiment I can think of a few politicians we could zip-tie a little and see how they fair? Just thinking.
Slow the metabolism, you live longer, but you don’t live more.
Near-starvation also makes mice live longer. It’s not so clear for humans. We can’t do controlled experiments on them. But even if it worked, would it be worth it?