Owning a dog was linked to 40 percent lower odds of developing disabling dementia over four years, in a study of 11,194 older adults in Tokyo. Cat owners showed no difference at all. Residents of Ota City, Tokyo, aged 65 to 84, filled out a detailed health survey in 2016. Researchers from the Tokyo Metropolitan Institute of Gerontology then followed them for about four years using Japan's long-term care records, where doctors rate whether someone's dementia is severe enough to need care. The study appeared in Preventive Medicine Reports in 2023. Only 8.6 percent of these older adults owned a dog. Dog owners can differ from everyone else in health, income, and lifestyle, so the team statistically balanced the groups on physical, social, and psychological traits before comparing them. Current dog owners had 40 percent lower odds of disabling dementia than people who had never owned a dog or no longer did. Cat owners matched non-owners. Dog owners who also exercised regularly had 63 percent lower odds compared with non-owners who didn't exercise, and dog owners who weren't socially isolated had 59 percent lower odds than isolated non-owners. Walking a dog counts as moderate exercise, and the researchers point to both the physical activity and the social contact that come with daily dog care. Cats rarely need a walk around the neighborhood. Healthier people may also be more able to keep a dog, and a study like this can't fully separate the two. Across 11,194 older adults, the lowest dementia risk showed up in dog owners who were also active and socially connected.