This hair pigmentation study adds to a growing body of evidence demonstrating that human aging and greying hair is not a linear, fixed process but may be halted or even temporarily reversed.

World Trade Center responders with current PTSD present with premature aging, altered gene activity called transcriptional aging, and accelerated epigenetic biological clocks.

The sirtuin SIRT6 — also known as a "longevity gene" — improves health markers and provides almost a 30% boost in longevity when mice have increased activity of the protein. 

The antioxidant and autophagic abilities of spermidine make this compound a possible contender for protecting and prolonging fertility with advancing maternal age.