the meaning of " Existence"

[bosunyum]

I am not sure what the two underlined existence means in the following sentnece. Could you help me to get it?

In searching for the ingredients to a long, healthy existence, scientists are studying the links between longevity and the psychological and social aspects of human existence.

Another questions is about health practices. what does it mean by instituting sound health practices will have a beneficial effect.
could it possible for you to paraphrase the above sentnece?

I always appreicate your help.

[Casiopea]

existence is synonymous with life. As for, health practices will have a beneficial effect, have you tried dictionary.com? It's a free on-line dictionary.

htp://www.dictionary/reference.com

[bosunyum]

Of course, i always do, but sometimes I am not sure which one to apply.
This is the way i understood the sentence;
Starting( institutuing) healthy lifestyle (health practice) or starting a good (sound) customs for your healthy body will bring you good health.
what do you think? Do you have any other suggestion?

[Tdol]

That's how I'd interpret it.