According to the researchers’ calculations, the metformin had made these monkeys’ brains six years younger on average, which could potentially translate to 18 years in humans
...the study’s findings are still based on a small sample size, and cynomolgus monkeys may have important biological differences that could affect the activity of metformin. These caveats mean that we can’t be certain about metformin’s fountain-of-youth effect in humans, at least not yet. But the results certainly do provide more incentive to keep digging.
https://gizmodo.com/a-common-diabete...ins-2000499935