Older adults who live with a dog were less likely to develop dementia serious enough to require care, according to a study from Japan. Researchers believe the walks, physical activity and social contact that naturally come with caring for a dog may help lower the risk of dementia.
A research team at Japan's National Institute for Environmental Studies recently published the findings in the International Journal of Environmental Research and Public Health (IJERPH), the science community said on the 23rd. The team tracked 11,224 adults aged 65 to 84 living in Tokyo's Ota Ward for an average of 7.5 years.
The researchers divided participants into three groups: those who currently own a dog, those who owned one in the past but no longer do, and those who had never owned a dog. Using data from Japan's long-term care insurance program, they then examined how often participants developed dementia at a level requiring care in daily life.
During the 7.5-year follow-up period, 1,989 people were diagnosed with dementia. Among older adults with no experience owning a dog, 18.1% received a dementia diagnosis, compared with 12.8% among those who currently own a dog — a gap of about 5.3 percentage points.
So why did dementia appear less often among older adults living with a dog? The clue lies in walking. Owning a dog naturally increases the time spent walking outdoors. It also creates chances to encounter others in parks or the neighborhood and to strike up conversations with neighbors or fellow dog owners with the dog as a go-between. In the end, the increased physical activity and social contact that come with living alongside a dog may have helped lower the risk of dementia.
Earlier findings support this. In 2023, the researchers published a study that tracked the same group of older adults for about four years. In that study, the tendency toward lower dementia risk was pronounced among dog owners who exercised regularly and were not socially isolated. By contrast, no clear link to dementia was found among those who kept cats, which do not require walks.
The researchers also estimated the effect of dog ownership on social costs. Assuming dog ownership among Japan's older population rises to 13.4%, they projected that public spending on health care and long-term care insurance could fall by about 592 billion yen over four years. Including household costs of keeping a dog, however — such as food and veterinary bills — society's overall costs would not necessarily decrease.
The study has limitations. Rather than reproducing earlier results in a new group, it is a follow-up that tracked the same group of older adults from the 2023 study over a longer period. Because dog ownership was measured at the start of the survey, changes over the following seven or so years — people who newly acquired a dog or stopped owning one — were not fully reflected. Above all, statistical methods alone cannot completely rule out reverse causation, since healthier and more active older adults are more likely to own a dog in the first place.
It would therefore be a stretch to read the study as meaning "get a dog if you are worried about dementia." Rather, it is worth examining which elements of life with a dog have a positive effect on brain health in old age.
Hwang Seung-sik, a professor at Seoul National University's Graduate School of Public Health, said the findings are better read not as a "prescription" for a dog itself but as evidence for policies that promote physical activity and prevent social isolation through mediating channels such as walking and social participation.
