Reduced oxygen levels to increase lifespan (Score 1)

It has been known for a while that lifespan can be increased with a special diet.

Looking at plants where metabolic rates are low and lifespans are often enormous, I started wondering whether it would be possible to increase animal lifespan by reducing oxygen intake
(from 21 to 18% in the air they breathe, for example).
This would slow down the metabolic rate and oxidation, and hopefully increase the lifespan.

Has this been tried yet in animals and what is your opinion about this?

Thank you.