Doctors say there is a 25% chance a frozen brain or body could be revived in the future: survey

Doctors believe there’s a one-in-four shot that human bodies and brains suspended in deep freeze could be successfully revived in the future, and most support intervening, pre-death, to improve “preservation outcomes,” a new survey suggests.

“Medicine often faces a tragic temporal mismatch: while approximately 70 per cent of terminally ill patients have a strong will-to-live despite their impending deaths, treatments that could meaningfully extend their lives may remain years or decades away from development,” the authors wrote in the journal, PLoS One.

Thus, hundreds of people, including many Canadians, have opted to be cryopreserved upon death — cooled to -196 degrees Celsius and stored in vats of liquid nitrogen with the hope of being successfully “reanimated” or restored to life at some later date.

While no such “preserved” patient has ever been revived, and, even if possible at all, successful revival may be decades away, “current preservation organizations report several hundred patients preserved globally, with thousands more signed up for future preservation,” the authors wrote.

For their study, the researchers surveyed 334 U.S. physicians in October 2025 — 150 primary care doctors and 184 other specialists, including neurologists, intensive care doctors, anesthesiologists and doctors who specialize in palliative, or end-of-life care.

Current preservation procedures known also as “biostatis” or “cryonics” take two main forms, the authors explained: the traditional approach (deep-freezing and flushing the body with biological antifreeze to minimize crystal formation) and aldehyde-based fixation, a newer brain-banking technique that involves injecting a fixative prior to cooling to lock everything into a life-like state and avoid further decay.

The latter approach is thought to be superior at preserving the brain’s “connectome,” which first author and neuroscientist Ariel Zeleznikow-Johnston of Monasha University in Melbourne has described as “all the individual (neural) connections that each of us have in our brains that make us unique.”

However distant, or outlandish, the prospect might seem now, “as long as you’ve preserved someone’s body and their brain in good quality (revival) remains a possibility, as long as you have their connectome,” Zelesnikow-Johnston said before a Royal Institution talk on abolishing death.

However, doctors lack “consensus” on whole body or brain preservation, “creating challenges for physicians whose patients inquire about preservation as an end-of-life option,” Zeleznikow-Johnston and colleagues wrote in PLoS One, including after medically assisted deaths.

For their study, survey participants were first asked, “How plausible do you find the idea that preservation could potentially allow for some form of revival in the future?” All in, 27.9 per cent answered “somewhat” or “very” plausible, while 47 per cent responded “somewhat” or “very” implausible.

Next they were asked to imagine a scenario where a patient is preserved within minutes of his or her heart stopping, and where imaging and brain biopsies show “intact brain structures down to the synaptic level.”

How likely would it be, the doctors were asked, that a “significant amount of the neurally-encoded information required for long-term memory and personality is still preserved in their brain, such that it may be technologically possible to revive this patient, even in the distant future?”

Overall, they said there was a 25.5 per cent chance.

Neurosurgeons rated the possibility that psychological information would remain after revival at 72 per cent, the highest of the group. Most of the other specialities were more skeptical.

Blood clots that form shortly after cardiac arrest can seriously hamper preservation’s probability of success, the authors said. When asked whether it should be allowable to give blood thinners to an “imminently terminal patient” who wishes to be preserved after death — which, to the best of the team’s knowledge, is not currently legally permissible anywhere in the world — 70.7 per cent said the practice should “probably” or “definitely” be allowed

Roughly 44 per cent said that, in cases of medically assisted dying, it should be legal to begin preservation procedures for those who want it after the patient is unconscious, but not yet dead.

“A lot of physician hesitancy may come from simple unfamiliarity with the scientific basis of modern preservation methods,” Zeleznikow-Johnston said in a news release.

“The doctors who have actually thought about this — and who regularly sit with dying patients — tend to be more receptive, not less.”

Experiments freezing and reviving fish date back to 1665. More recently, German scientists reported in March that they succeeded in restoring some activity in previously frozen slices of an adult mouse brain.

Zeleznikow-Johnston and his co-authors said that the plausibility of it working with humans gains some support from procedures like deep hypothermic circulatory arrest, where patients undergoing complex surgeries on blood vessels around the heart or in the brain are cooled to the point where blood stops circulating and their heart and brain activity ceases, so that surgeons can do the delicate repairs in a bloodless field. Their bodies are then slowly warmed again after surgery.

While patients “routinely recover full neurological function” after 30 minutes of cardiac arrest, that’s a short-term form of preservation, and skeptics of the preserve-restore-revival promise of cryonics are plentiful.

The cost isn’t cheap, upwards of $200,000 for whole body freezing and storage. Given what’s known about how the dying process damages brain tissue due to lack of oxygen, in addition to any further damage sustained from freezing, it’s “next to impossible” to believe brain preservation and restoration would ever work, no matter how advanced the science, bioethicist Arthur Caplan told National Post in 2023. The risk of adverse events like dementia or severe cognitive impairment “are just huge,” Caplan added.

How, and in what form, people will “reawaken” is unknown: Their brain still attached to their now freshly, biologically restored body, or uploaded to a digital form that’s placed inside a robot? Whatever form, “if the memories and experiences which define us are held on to, a person has survived,” Zeleznikow-Johnston said in an interview with the Guardian. “A robotic or digital brain, if done right, I’d argue, is still you.”

Payments to doctors for filling out the survey (US$28 for primary care physicians and US$48 for specialists) was supported by a a grant from CryoDAO, an organization that funds research in cryopreservation.

National Post

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