Association between pet ownership and incident dementia: A systematic review

Dementia affects more than 55 million people worldwide, and prevention remains a global priority. Pet ownership is a modifiable factor hypothesized to improve cognitive health, but longitudinal evidence is mixed. We searched PubMed, Embase, CINAHL, Web of Science, and PsycINFO for prospective cohort, case-control, or nested case-control studies in adults without dementia reporting incident dementia and/or dementia-related outcomes. Two reviewers screened, extracted data, and assessed risk of bias. Since studies reporting incident dementia were too few (n = 3) and heterogeneous, we conducted a narrative synthesis rather than a meta-analysis. We included six studies. Outcomes spanned conversion to mild cognitive impairment/dementia and worsening neuropsychological trajectories. Two studies suggested a protective association between pet ownership, especially dogs, and incident dementia, while one study found no significant association. For secondary outcomes, dog or cat ownership, with dog walking, was associated with slower cognitive decline, whereas exposure to non-companion animals was associated with increased risk of cognitive impairment. Risk of bias was moderate to high. The type of pets and related behaviors may be more critical than ownership alone.