In late 2019, scientists began searching for 10,000 Americans willing to enroll their pets in an ambitious new study of health and longevity in dogs. The researchers planned to track the dogs over the course of their lives, collecting detailed information about their bodies, lifestyles and home environments. Over time, the scientists hoped to identify the biological and environmental factors that kept some dogs healthy in their golden years — and uncover insights about aging that could help both dogs and humans lead longer, healthier lives.

Today, the Dog Aging Project has enrolled 47,000 canines and counting, and the data are starting to stream in. The scientists say that they are just getting started.

“We think of the Dog Aging Project as a forever project, so recruitment is ongoing,” said Daniel Promislow, a biogerontologist at the University of Washington and a co-director of the project. “There will always be new questions to ask. We want to always have dogs of all ages participating.”

But Dr. Promislow and his colleagues are now facing the prospect that the Dog Aging Project might have its own life cut short. About 90 percent of the study’s funding comes from the National Institute on Aging, a part of the National Institutes of Health, which has provided more than $28 million since 2018. But that money will run out in June, and the institute does not seem likely to approve the researchers’ recent application for a five-year grant renewal, the scientists say.

“We have been told informally that the grant is not going to be funded,” said Matt Kaeberlein, the other director of the Dog Aging Project and a former biogerontology researcher at the University of Washington. (Dr. Kaeberlein is now the chief executive of Optispan, a health technology company.)

A spokeswoman for the National Institute on Aging said that the N.I.H. does not comment on the decision-making process for individual grant applications.

The N.I.A. could still choose to provide more funding for the Dog Aging Project at some point, but if the researchers don’t bring in more money in the coming months, they will have to pause or pare back the study.

“It’s almost an emergency,” said Stephanie Lederman, the executive director of the nonprofit American Federation for Aging Research. “It’s one of the most important projects in the field right now.”

A petition asking for continued support from the National Institutes of Health has garnered more than 10,000 signatures, said Dr. Kaeberlein, who organized the effort.

Still, the researchers are not counting on the agency to come to their rescue, and they have learned how challenging it is to conduct large, long-term studies — which could take many years to pay off — when grants are usually awarded on a short-term basis.

So the three founders of the Dog Aging Project — Dr. Promislow, Dr. Kaeberlein and Dr. Kate Creevy, a veterinarian at Texas A&M University — have now created the nonprofit Dog Aging Institute to raise money for research. They hope to use the organization both to keep their own study alive and to fund other scientists who are interested in exploring similar subjects.

“The data are just coming fast and furious,” Dr. Promislow said. “If anything, we’ve had to slow it down because of these funding challenges. And it’s the worst possible time to be slowing things down, because now is the time when the really exciting stuff is just starting to happen.”

The Dog Aging Project was born from two observations. First, people would give almost anything to spend more good years with their dogs. Second, canine companions could be useful models for human aging. Dogs are prone to many of the same aging-related conditions people experience, including cancer and dementia, and are exposed to many of the same environmental stressors, such as air pollution and noise. But because dogs age more quickly, studies of canine aging can yield results over shorter time frames.

That was the case that the founders of the Dog Aging Project made when they asked the National Institute on Aging to fund a large, long-term study of pet dogs. In 2018, the institute awarded the researchers a five-year grant, which was then extended a year.

The study is expansive. Owners of all enrolled dogs are asked to complete an annual, 10-part health and life experience survey, encouraged to share the animals’ medical records and invited to participate in an array of other surveys and activities. The researchers also aim to sequence the genomes of more than 10,000 dogs; 1,000 of those animals will also provide an array of biological samples — including blood, urine, feces and hair — every year. They are also enrolling hundreds of dogs in a randomized, placebo-controlled trial of rapamycin, a drug that has proved capable of extending the lives of lab animals.

The researchers estimated in their 2018 grant application that it would take at least three months to build the physical, digital and human infrastructure for the study. The process ended up taking three years. “I don’t think anybody appreciated how hard it was going to be,” Dr. Promislow said. (The pandemic, which shuttered or strained veterinary clinics, did not help, he added.)

But the project is up and running. The research team, which includes more than 100 people from more than 20 institutions, has sequenced the genomes of more than 7,000 dogs and deposited 14,000 samples in the project’s biobank. The scientists have added more than 36.5 million data points to their open-access database and started to publish some early findings. They have found, for instance, that a condition called canine cognitive dysfunction, also known as doggy dementia, is more common in sedentary dogs than active ones and that dogs that are fed once a day are less likely to have a variety of health problems than those that eat more frequently. More papers are in the works.

But when the researchers sought a five-year grant renewal last year, their application did not score well enough in the first round of peer review to advance to the next stage of the funding process. “The reviewers were asking how much we’d accomplished in five years,” Dr. Promislow said. “Given the size of the project, I think the reviewers were wondering where the major papers are.”

Steven Austad, a biogerontologist at the University of Alabama at Birmingham who is not part of the research team, said he was surprised that the researchers’ grant might not be renewed. “The importance of the things they publish and the depth of detail will increase over time, but I thought they got off to a really good start,” he said. “A large study like this really deserves a chance to mature.”

Dr. Austad’s miniature dachshund, Emmylou, is enrolled in the Dog Aging Project. But at 2 years old, he noted, Emmylou is “not going to teach them a lot about aging for a long time yet.”

The project’s innovative approach might have worked against it, Dr. Austad added. Reviewers accustomed to evaluating short-term research on lab mice and long-term studies of humans may not have known what to make of an enormous epidemiological study of pet dogs.

Whatever the reason, the refusal to commit to more funding is “wrong,” Dr. Kaeberlein said. “It’s just really, really difficult to justify this decision, if you look at the productivity and the impact of the project.”

That impact extends beyond the findings themselves, he added. “This project has engaged almost 50,000 Americans in biomedical scientific research.”

Over the last few years, Shelley Carpenter, of Gulfport, Miss., has provided the researchers with regular updates on and medical records for her Pembroke Welsh corgi, Murfee. (She also collected a cheek swab for genomic sequencing.) Ms. Carpenter, whose previous corgi died from a neurodegenerative disease similar to A.L.S., hoped that the project might produce new medical knowledge that could help both dogs and people.

If the N.I.H. suspends funding, they will be “throwing away” years of research, said Ms. Carpenter, who signed the petition. “Why did they even start it if they’re not going to follow through?”

The researchers are planning to apply for more N.I.A. grants, Dr. Promislow said, but they have realized that they will need to develop additional funding sources to secure the project’s future. Although the Dog Aging Institute is still in nascent stages, the researchers ultimately hope to raise $40 to $50 million for an endowment that could be used to fund a variety of research related to canine health and longevity, including the Dog Aging Project.

The institute’s immediate priority is to raise enough money to keep the Dog Aging Project afloat. It would take about $7 million to conduct the research the team had planned to do over the next year, but $2 million would be enough to “keep the lights on,” Dr. Promislow said. The institute is still awaiting its official tax exempt status but is already seeking donations. “We haven’t yet identified a dog-loving billionaire interested in supporting aging research,” Dr. Promislow said. “But we’re certainly going to try.”