Each person has several "channels" - tasks that he constantly uses, consciously or not. For example, a young mother simultaneously thinks about how best to cook borscht, that she needs to make an appointment with a doctor, and remembers about a sleeping child - this is multitasking. That is, it is inherent in every person. The more developed the brain, the more "channels" that work simultaneously. Multitasking develops the brain. So, on the contrary, it prolongs his life. Another thing is that you need to be able to use a large number of channels. They consume energy very cool if they start to work without proper management, and energy is life.
Kills, at about the same speed as breathing, for example. :) Well, if a little more seriously, then every first person (during the waking period) is constantly in the multitasking mode. And they live somehow, some even live a long time.
I heard that women are more capable of this, and men are less ...
Now it is more a matter of faith. As far as I understand, this is just a working hypothesis. For example, I do not understand the mechanism of brain damage. They found some sort of problem in the frontal lobes of multitasking people who supposedly taught themselves to multitask. But the frontal lobes are just responsible for volitional behavior. That is, the will should be reduced - then why does he continue such a complex behavior, and not just lie on the couch. It seems to me that multitasking, in this case, is nothing more than an unstable attention that jumps from object to object, forcing them to constantly switch from one job to another, this, of course, reduces accuracy and leads to fatigue. But these are the features of a particular person, his original method of adaptation.
It does not always make sense to consider yourself separately from your brain, a person is the brain (or rather, even the whole organism). I doubt that the brain is capable of suddenly starting to solve the assigned tasks in a harmful way, it is more likely to decide to quit the job. The only thing that is undoubtedly harmful for him is a long rest. Well, if you do not use intellectual resources for a very long time, then problems really begin. It is enough to look at the elderly, some of them, at one time, occupied some posts, made decisions, and in old age they cannot solve almost anything, they are completely dependent on children. Unused neurons have died ...
So I guess you shouldn't panic).