Among older adults, dogs boosted adherence to 100 percent, which led to a 28 percent improvement in walking speed, Johnson said. Walking speed was recently linked to lifespan.
"It improved their balance and their confidence in walking," Johnson said. "It helped them maintain their independence."
As for the prospect of using trained dogs for cancer screening, Johnson said it would be wonderful.
"We're always looking for effective and inexpensive screening devices," Johnson said. "Training dogs is not inexpensive, but the cost to the end user is going to be a lot less than many of the tests we have."
She cautioned that the sniff test reported, or others like it, should not be used in making a diagnosis. Rather, they could be used to supplement current screening systems.
But the study authors hope that future research will tease out the cancer-signaling chemicals that Marine could smell. Then a machine could be programmed to detect the chemical quickly and cheaply, they wrote.
But until a machine can mimic dogs' extraordinary ability to monitor human health, people should pay more attention to their pets and take every opportunity to reward them, Becker said.
"We've always known dogs made us feel good, we just didn't know they were good for us," Becker said. "I think in the coming years we're going to be in awe of just how strong the connection is."