Investigating the Potential Protective Effect of Dog Ownership on Incident Disabling Dementia and Its Cost-Effectiveness

This prospective study investigated the association of dog ownership with the onset of disabling dementia and mortality using propensity score weighting based on the physical, social, and psychological characteristics of dog owners, and then examined the potential causality of this relationship using an instrumental variable model. Additionally, we examined the costs and effects of dog ownership using cost-effectiveness analysis. Overall, 11,224 older adults selected using stratified and random sampling strategies in 2016 were analyzed. Dog ownership was defined as current, past, and never. Disabling dementia was defined according to a physician rating under the long-term care insurance system in Japan and mortality was ascertained by the Japanese national vital statistics during the approximately 7.5-year follow-up period. Current and past dog owners had an odds ratio (OR) of 0.53 (95% CI: 0.43–0.66) and 0.97 (0.86–1.09) of the onset of disabling dementia compared to never owners. ORs for mortality were 0.63 (0.51–0.79) in current dog owners and 0.88 (0.78–0.99) in past dog owners. Causal analysis showed that current dog owners (OR = 0.52, 95% CI: 0.27–0.98) and past dog owners (OR = 0.75, 95% CI: 0.55–1.03) had low ORs for incident dementia compared to never dog ownership. Corresponding values for mortality showed low ORs, but no significant effect on current dog owners (OR = 0.59, 95% CI: 0.35–1.01) and past dog owners (OR = 0.77, 95% CI: 0.60–1.00) compared to never owners. Results of cost-effectiveness analysis showed that dog ownership produced small but positive gains in quality-adjusted life years (QALYs) and was dominant (cost-saving and QALY-increasing) from the public payer perspective, reducing publicly financed medical and long-term care costs while increasing QALYs; when private dog-ownership costs were included in a scenario analysis, the incremental cost-effectiveness ratio (ICER) was ¥6,744,174 per QALY compared with no-dog status. This prospective study shows that dog ownership has a potential protective effect against the onset of disabling dementia in older adults. The study also revealed the potential of dog ownership to reduce public spending with regard to long-term care and medical expenditures.