I know an 84 year old man in the prime of life, he speaks 37 languages, five of them nearly natively (including three that I happen to speak at a high level from my study and travels, and in which I have conversed with him), and is learning more every day. He is the personal language consultant of a billionaire, and recently picked up a new language fluently for him in less than a year. He also made impressive strides in an uncommon language I speak due to my family which is notoriously difficult, and has learned most of the dictionary and can read a newspaper as well as converse fluently. (The above information means there's a good chance someone here might recognize him, though the overlap with startups would only be via the billionaire.)

I asked him what his secret is for being so sprightly. He said, "I don't have one." Then on reflection he says, "Oh, I take a cold shower every day."

Of course 1 data point is not a study. But you might try it for a year and see if anything happens :)