This is an updated version of a story first published on March 22, 2026. The original video can be viewed here. 

Everyone knows the old adage about dogs being man's best friend, but you may not know that dogs might also be one of man's best hopes to treat age-related illnesses. That's because our canines develop many of the same diseases we do, including dementia. As we first reported last March, dogs' brains are a lot like ours, so studying how dementia and other diseases naturally progress in them, may also help us. 

That's what the Dog Aging Project is all about: unlocking secrets to a longer, healthier life for humans, and our four-legged friends. 

At hundreds of vet clinics and hospitals around the country -- including here at Colorado State University College of Veterinary Medicine and Biomedical Sciences, people are bringing in their dogs. 

The Dog Aging Project is a collaboration of dog owners, scientists and veterinarians studying dogs -- more than 50,000 of them so far -- by collecting data on their diets and exercise, analyzing blood samples and doing MRIs of dogs' brains. Matt Kaeberlein, a biologist who has spent decades trying to understand -- and reverse -- the causes of aging, co-founded the project in 2014.

Anderson Cooper: Where did the idea of the Dog Aging Project come from?

Matt Kaeberlein: I had this lightbulb moment, which I still remember vividly. I realized, "Oh my God, we know about three or four or five ways to slow aging in laboratory animals. Some of those are going to work in dogs."

Anderson Cooper: You think that's possible.

Matt Kaeberlein: Absolutely. I have no doubt that's possible. The biology of aging is so conserved or shared across the animal kingdom. Much of this works the same way in dogs. Much of it works the same way in people.

To help study how the brain ages, Kaeberlein recruited Stephanie McGrath, a veterinary neurologist from Colorado State University. 

Anderson Cooper: I think a lot of people would be surprised to know that there are neurologists for animals.

Stephanie McGrath: Yes, a lot of people are surprised. 

Anderson Cooper: And you believe looking at dogs, and looking at dogs' brains, can help us not only help dogs but humans as well?

Stephanie McGrath: Yes, of course. Absolutely. There's no doubt.

Anderson Cooper: Why? 

Stephanie McGrath: Because right now we are using mice, and we are putting them through treatment trials and then we go directly to human trials. 

Anderson Cooper: I've read that as many as 90% of the things that work in mice do not end up working in humans. 

Stephanie McGrath: Right.

Anderson Cooper: So, to have something in between would be hugely beneficial? 

Stephanie McGrath: Right. And not just another species, but a species that very closely mimic naturally occurring diseases of aging in humans. Cancer, dementia, all these diseases that we see as humans age occur in dogs.

One reason: they live alongside us and are exposed to the same environments. They exercise with us, eat our food, drink the same water. Also key, McGrath says, is the fact that dogs have shorter lives because they age faster than humans. 

Stephanie McGrath: We can get a ton of information that would take decades to do in humans.

Anderson Cooper: In a human being if you wanted to do a lifelong study, obviously you would have to do it from the age of one to 60, 70, 80. 

Stephanie McGrath: Exactly. So many decades versus five, 10 years.

McGrath has been tracking hundreds of dogs to see how their cognitive ability changes as they age, including 12-year-old Murphy, a German shepherd-poodle mix. 

Pat Schultz: He gets his puppy zoomies about once a week now, versus once a day. 

Stephanie McGrath: Ok. Alright. They're still in there though. 

Pat Schultz: They're still there. 

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For Pat Schultz, like many of the dog owners we met, enrolling Murphy in the Dog Aging Project was personal. Her husband Bill suffered from Alzheimer's disease, progressing to the point he stopped recognizing Pat as his wife. 

Anderson Cooper: What do you do in a situation like that?

Pat Schultz: Just go along with it. He asked me out on a date.

Anderson Cooper: Really?

Pat Schultz: Yeah. "Can we go on a date?" "Sure, let's go have dinner." You know?

Throughout his decline, Murphy was Bill's constant companion.

Anderson Cooper: Murphy was a caregiver in some ways. 

Pat Schultz: Yeah. Murphy was like his nanny dog. Bill would forget his phone. I have a tracking collar on Murphy. So as long as Murphy had that tracking collar on, I knew where Bill was.

Anderson Cooper: So, while Bill is dealing with Alzheimer's, you hear about the Dog Aging Project.

Pat Schultz: I think I was looking at clinical studies. And I found something about dog studies. I thought, "Oh, dog studies. I hadn't heard of those, you know?" Murphy was getting older. And knowing that he's a big dog, they don't have as long a lifespan usually. 

For the past three years, Murphy has undergone testing to assess his physical and mental fitness. 

In games like these, dogs are shown where a treat is hidden and seconds later allowed to go and get it — if they can remember where it is. 

When it was Murphy's turn, he struggled, wanting to stay with Pat, too anxious to do the test. 

On the second try, he got a little turned around, but eventually found the treat. 

Anderson Cooper: The anxiety that Murphy showed, is that a potential sign of dementia?

Stephanie McGrath: Yes, is the short answer. In the last few visits at CSU, he's really progressed in terms of his challenges with his tasks both here and at home. 

Another dog, Ralph, was also tested. At 14, he's already shown signs of advanced dementia. 

Ralph quickly forgot about the treat, wandered off, and picked up a piece of lint off the floor.

All the information collected in the Dog Aging Project -- including from these tests -- goes into a public database accessible to researchers around the world. It's been used in more than 50 scientific studies so far, many of which found correlations between lifestyle, environment, and disease risk.

One finding: dogs that live with other dogs appear to suffer from fewer diseases. And when it comes to cognitive decline -- dogs that don't exercise were found to have a six times greater chance of developing dementia.

When some of the dogs in the aging project die, their brains are donated and examined. Dr. Dirk Keene is a neuropathologist from the University of Washington. For the past 20 years, he's studied thousands of human brains looking for causes of Alzheimer's. His motivation for participating in the Dog Aging Project was watching his mother suffer from Alzheimer's and also seeing his dog Spring decline from what looked like, to him, the same disease, what some call "doggy dementia." 

Dirk Keene: So that's Spring when she was a healthy, happy dog.

Anderson Cooper: Tongue out, tail wagging.

Dirk Keene: She's-- she was–

Anderson Cooper: As she should be–

Dirk Keene: --she was a happy dog, yep. And this is Spring–

Anderson Cooper: Oh, wow.

Dirk Keene: --near the end of her life. She would get confused and sort of lost. She would stare at walls. She would just stop and stare into space, she would lean against things. This happens to people. It's not just memory when we start to have dementia. Dementia's a very complex thing that includes confusion; it includes the loss of the ability to remember sort of spatial references. Very similar to what we're seeing in dogs, happens in people.

Anderson Cooper: This is half of a human brain?

Dirk Keene: This is-- this is half a human brain. 

Anderson Cooper: That's the dog brain?

Dirk Keene: That's the dog brain.

Anderson Cooper: Half a brain. Wow.

Dr. Keene showed us how similar dogs' brains are to humans'.

Dirk Keene: You can see the dog brain has the same frontal lobe, temporal lobe, occipital lobe.

Anderson Cooper: It's the same basic shape as the human brain.

Dirk Keene: It's very, very similar. 

And it turns out dementia changes brain size and structure in very similar ways in both species.

Dirk Keene: This is a person in their eighties who was not demented. This is a person who was in their seventies who was demented. And so, the most important sort of thing to notice is how much different in size they are. 

Dirk Keene: I'm going to let you hold this if that's okay. So just grab on there, yep. You can sort of feel how much different.

Anderson Cooper: Oh wow. The weight difference between a healthy brain and an atrophied brain is stunning.

As disease kills off neurons, the brain shrinks, and the space in the middle cavity enlarges. 

Anderson Cooper: I mean, it looks like something has completely fallen out here.

Dirk Keene: Yeah, it's remarkable. 

Anderson Cooper: It's so depressing.

Dementia in dogs also results in enlarged spaces and brain shrinkage.

Dirk Keene: This is Spring's brain.

Under a microscope, Spring's brain, one of the first to be donated to the Dog Aging Project, shows beta amyloid plaques, a hallmark of Alzheimer's — and it looks strikingly similar to the plaques in a human brain as well.

Progress in preventing Alzheimer's and other forms of dementia -- which will affect an estimated 40% of Americans over 55 – has been slow. The Dog Aging Project hopes to change that by testing the drug rapamycin. In mice it's been shown to slow cognitive decline and increase life expectancy by a remarkable 60%. That's led some longevity researchers and influencers to suggest rapamycin for human use. 

To understand whether it might work in dogs, Julie Moreno, a molecular biologist from Colorado State University, helped conduct a pilot study of 12 dogs, all with signs of dementia. Ten-year-old Qbert was among those given a placebo. Thirteen-year-old Monkey received rapamycin. After the dogs died, Moreno examined their brains and found that Monkey's brain showed fewer microglial cells, which produce inflammation commonly associated with dementia. 

Julie Moreno: So if you just kind of focus in on this side, you see quite a bit of those teal-colored microglial cells. And then if you look over here, you just see less, right?

Anderson Cooper: Yeah.

Julie Moreno: Like, there's just less number of them. 

Two other dogs receiving rapamycin -- including Ralph -- have since died. Their brains also showed fewer cells associated with inflammation. 

Anderson Cooper: So rapamycin, at least, in this study, worked on dogs?

Julie Moreno: Yeah. 

Anderson Cooper: What did you think, when you first saw this?

Julie Moreno: I was super excited.

Anderson Cooper: You were? What's your hope in doing this study? 

Julie Moreno: If it works in a dog, and it's safe, and it's helping their cognition, then, maybe, it would help humans. 

The Dog Aging Project is now conducting a larger clinical trial funded, in part, by the National Institutes of Health, giving hundreds of dogs -- including Murphy -- either a placebo or rapamycin to see if the drug can extend life.

There are three other drugs being developed by the for-profit company Loyal, a biotech start-up founded in 2019 by 31-year old Celine Halioua. 

Celine Halioua: My vision is that this is, you know, it's a daily beef-flavored pill that are given preventatively to keep them healthier longer, similar to a statin, you know, for older Americans.

Anderson Cooper: And you think it will actually help extend a dog's life?

Celine Halioua: Yeah.

Anderson Cooper: How long?

Celine Halioua: Approximately one healthier year of life. Maybe it'll be more. Maybe it'll be less.

One of their drugs, in a clinical trial, is being given to dogs over the age of 10, who are monitored for signs of aging. 

The FDA has signed off on the drug's safety data and says it has a "Reasonable Expectation of Effectiveness," but final results from the trial won't be known for several years. 

Anderson Cooper: That extra year would be a healthier year than otherwise?

Celine Halioua: An aging drug is about delaying and slowing the rate of decline that a dog or a human has over time, to give them more healthier years. It's not something that you would give to a dog or a human on their deathbed to give them another year. It-- it doesn't work like that.

Silicon Valley is betting big on longevity. Halioua's company has raised more than $250 million to bring its drugs to market.

Celine Halioua: If we can achieve this, this is a massive, multi-billion-dollar company. If we only do that, we're all happy. But, oh, by the way, this also unlocks the possibility of us working on human longevity one day. I think going dogs first is the fastest way to work on and understand the biology of human aging. 

After a long struggle, Pat Schultz's husband Bill died two years ago due to complications from Alzheimer's. As part of the Dog Aging Project, she won't know for another few years whether Murphy got the rapamycin or not, but for now, she told us, she's simply focused on making sure they both age as best they can. 

Anderson Cooper: You've cared for a human with Alzheimer's. You're caring for a dog in the study who, you know, is aging. What have you noticed in terms of similarities?

Pat Schultz: The thing I notice is that they both need to be loved and cared for. Just holding Bill's hand and patting his hand was enough just to decrease that anxiety, decrease that fear that, you know, was there. 

Anderson Cooper: And that works with Murphy, too?

Pat Schultz: And it works with Murphy, too. Yep.

Produced by Denise Schrier Cetta. Associate producer, Elizabeth Germino. Broadcast associate, Grace Conley. Edited by Warren Lustig.