The oxidative stress, or the rate of living, theory of ageing suggests that a lower metabolic rate means longer life span and higher metabolic rate means a shorter life span, i.e. “live fast, die young”. This holds in most cases, since larger animals in general have a low metabolic rate and tend to live longer than smaller animals with a corresponding higher metabolic rate. An elephant for example can live up to 80 years. Since it has a slow metabolism, the elephant heart beats roughly the same number of beats as the heart of a mouse. The mouse however, with a much faster metabolism, “uses up” it’s heart beats in only 2-3 years.
However, since there are many exceptions from the “live fast, die young”-theory it tells us that it is incomplete. This article looks at ageing from a breathing perspective and suggest that the tolerance for carbon dioxide is a major factor determining the life span.