Whether you walk on two legs — or gambol happily on four and happen to bark — being physically active lowers the risk of developing dementia with age, according to two new studies involving people and dogs.
Dogs get dementia, too
Many of us might be surprised to learn that dogs develop dementia (including me, although I have three dogs). But it is common with aging, just as in people, and the disease hallmarks are similar in both species.
“Getting lost is one of the most common symptoms” of canine cognitive dysfunction, the formal name for dog dementia, said Matt Kaeberlein, a professor at the University of Washington in Seattle, co-director of the Dog Aging Project, and co-author of the dementia study.
Dogs with cognitive dysfunction “get lost in their own homes,” he continued, sometimes staring blankly at a wall or crawling under a desk or table and becoming unable to find their way back out.
Well-trained pets with early dementia also frequently stop responding to simple commands, he said, while once-sociable dogs withdraw to corners, confused and alone.
Previous research established that age is the primary risk factor for cognitive decline in dogs, as in people. But most past studies were small, examining only a few dogs, making it difficult to tease out any contributions from pets’ breed, sterilization status, general health, lifestyle or other factors.
So, Kaeberlein and his co-authors turned to their rapidly growing pack. Initiated in 2018, the Dog Aging Project recruits pet owners nationwide and asks them to complete detailed questionnaires about their dogs’ lives, health and dementia symptoms. (Sample question: “How often does your dog walk into walls or doors?”)
By late 2020, tens of thousands of dogs had joined. The researchers drew data for 15,019 of those with complete records, covering multiple breeds and ages, ranging from youthful dogs to seniors. About 1.5 percent of the animals turned out to have dementia, according to their questionnaire scores.
The scientists then checked to see which aspects of the dogs’ lives correlated most closely with memory loss. Unsurprisingly, aging won. As a dog aged, its risk for dementia “rose exponentially,” Kaeberlein said. Problems with hearing and sight also affected memory.
But among other lifestyle factors — breed, sterilization, gender, physical activity, among others — only physical activity showed an effect. Dogs that, by their owners’ estimation, were inactive, were nearly 6.5 times more likely to have dementia than highly active dogs of the same age.
The results strongly suggest that “taking your dog for a walk” or playing Frisbee or fetch or, in any other way, keeping Rover moving, “is likely to be beneficial” for its brain, Kaeberlein said.
Just 3,800 steps can lower risk for dementia
That conclusion dovetails neatly with the findings of the latest, large study of human brains and walking, published in September in JAMA Neurology. In it, scientists in Denmark and elsewhere drew anonymized health records for almost 78,500 middle-aged or older men and women who had joined the UK Biobank, an immense database of health data. These volunteers provided general health information and wore an activity tracker for a week to record their daily steps.
The researchers followed these volunteers for about seven years, checking hospital and other records for dementia diagnoses, then tabulating the relationship between how much — or little — people walked and their chances of developing dementia.
More, the scientists found, was better. Men and women who averaged about 9,800 steps a day were half as likely to develop dementia as sedentary people. Even those accumulating only about 3,800 steps, or a little less than two miles of total walking per day, were 25 percent less likely to develop dementia than people walking less. If some of these steps were speedy, completed at a pace of about 112 steps per minute, the risk of dementia fell even more.
“If you walk about 10,000 steps, your risk drops 50 percent,” said Borja del Pozo Cruz, a researcher affiliated with the University of Southern Denmark and the University of Cadiz in Spain, who led the new study. “But if 30 minutes of that time is done briskly, you can achieve an extra 10 to 15 percent risk reduction.”
Which is where dogs come in handy.
Taking humans for more walks
It seems “very plausible” that walking a dog would help protect everyone’s brains, said Carri Westgarth, a senior lecturer at the University of Liverpool in England, who studies interactions between people and dogs but was not involved with the new studies.
In a 2019 study she led, dog owners were four times more likely to meet the standard exercise guidelines of 150 weekly minutes of moderate exercise, or — in practical terms — five, weekly 30-minute brisk walks. Why? Because they walked their dogs.
The new studies have limits. They show only a relationship between more activity and less memory loss. Other factors are probably also in play, including that dogs and people with early dementia might be less able to move much. The studies also do not examine how walking might stave off cognitive decline, although researchers suspect biochemical and other brain changes with exercise.
The good news is that, with rare exceptions (such as if a dog or its owner is ill or disabled), “there is no downside” to frequently walking your dog, if you have one, Kaeberlein said, and the potential upside could extend well into the future.
For my own part, I will be upping the length and tempo of my ambles with Archie, Finn and Flicka, my own frolicsome pack of dogs. As they sniff, sprint, wag and wander, we will, I hope, be building memories and bonds that linger for all of us, even as the years fade.
The Dog Aging Project is recruiting additional subjects, Kaeberlein said. If you would like to enroll your dog, you can find information here.
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