Aging is a killer. Incidence rates for heart disease, cancer, kidney disease and dementia all skyrocket as people reach their 70s and 80s. There's no cure for getting old, but there may be a surprising simple, albeit somewhat medieval, way to turn back the body's internal clock and reverse the deadly effects of degenerative diseases.

By injecting blood from human teens into old mice, researchers in California are reporting remarkable enhancements to the older rodents' memory and cognition. The blood, donated from human teenagers, appears to have kickstarted the creation of new neurons in the aged mice. The research echoes previous findings that transfusions of young blood can reverse the thickening of heart muscles, a major cause of heart failure.

Now scientists are hot on the trail of the specific proteins or other factors that are responsible for the "Fountain of Youth" effect of young blood. If those factors can be identified and isolated, we could be on the verge of new drug therapies that will redefine old age.

RELATED: Teen Girl's Body Frozen After Death in Legal First

"It's sort of a bold question," said Joseph Castellano, a post-doctoral fellow at the Stanford School of Medicine. "Can we actually halt or even reverse certain aspects of aging? We think of the aging process as something that's fixed. Now we've seen that you can actually change the rate of aging phenotypes [physical characteristics]."

Castellano is a member of Tony Wyss-Coray's Neuro Immunology & Degeneration Lab, which published a landmark paper in 2014 proving that young mouse blood could significantly improve brain function in older mice.

More recently, Castellano and his colleagues repeated the mouse experiment using human blood donated from healthy newborn babies. The old mice, which had shown clear signs of cognitive decline, now breezed through spatial memory tests, and cellular analysis showed clear boosts of neural activity.

"We see that there's definitely something going on in the brain and specifically in the hippocampus, which is responsible for spatial memory," said Castellano, noting that the younger the blood, the more dramatic the rejuvenating effect.

RELATED: Seeking Immortality? So Have Others...

The "creepy factor" is undeniably high with this kind of research, but no one is suggesting that old people should be hooked up to IVs filled with baby blood. Instead, researchers like Castellano are trying to identify the proteins responsible for young blood's anti-aging effects and turn those molecules into life-saving therapies.

"We're narrowing in on a couple of different factors present in human plasma that seem to be of interest," said Castellano, whose focus is on the blood-borne proteins that enhance brain function. "My suspicion is that there will be a lot of different factors coming out in the next several years that modify different processes in different tissues."

The Harvard University researchers who first reported the rejuvenating effects of young blood on heart tissue credited a protein called GDF11. The same protein, when injected into old mice, also seemed to spur neuron growth and stem cell regeneration. Attempts to replicate the results have met with mixed success, prompting doubts that GDF11 alone is the miracle molecule.

A private company called Alkahest, which was co-founded by Castellano's advisor Tony Wyss-Coray, is now in the early stages of the first human trials with transfusions of young blood. Wyss-Coray recently proved that young blood can reverse the effects of Alzheimer's in mice. The dream is to do the same in people.

"I don't think we'll stop aging, but I think it's certainly reasonable to assume that we can limit the morbidity of other disorders by delaying aging," said Castellano.

WATCH: Can This Jellyfish Live Forever?