Exploring the Impact of Pet Ownership on Cognitive Decline

Older adults tend to experience cognitive decline . As the population ages and life expectancy increases, a major public health problem is the decline in cognitive function in older adults. The number of people with dementia worldwide is estimated to increase from 57 million in 2019 to 153 million in 2050. Impaired cognitive function not only seriously harms people’s well-being, but also places a huge burden on their lives. health. caregivers, as well as society’s financial and health systems. There is currently no effective therapy available to successfully reverse cognitive decline or treat dementia. Therefore, identifying high-risk populations and modifiable risk factors is crucial for formulating public health interventions and promoting healthy aging.

In recent decades, the proportion of people living alone has shown an increasing trend. In 2021, the proportion of single-person households in the United Kingdom (UK) and the United States reached 29.4% and 28.5%, respectively. A recent meta-analysis of 12 studies reported that older adults living alone are at high risk of developing dementia and that the fraction attributable to the population living alone is 8.9%. This figure will increase as the proportion of older adults living alone is increasing. Currently, it is essential to identify modifiable factors that reduce the risk of dementia in older adults who live alone.

Loneliness is a potential mediator in the association of living alone with dementia among older adults. Unlike living alone, owning a pet (for example, raising dogs and cats) is associated with less loneliness, a major risk factor for dementia and cognitive decline. However, the association between pet ownership and the rate of cognitive decline has not been fully explored and existing findings remain controversial. Several cross-sectional studies have found that pet ownership is associated with better verbal memory, story memory, executive function (i.e., serial subtraction of sevens and clock drawing tests), processing speed, and orienting function.

However, some cross-sectional studies have reported that pet ownership is not associated with verbal memory or executive function (i.e., backward number counting tests). To date, prospective longitudinal studies are lacking to elucidate the association between pet ownership and the rate of cognitive decline. Furthermore, it is unclear whether there is an interaction between pet ownership and living alone and to what extent pet ownership mitigates the association between living alone and the rate of cognitive decline. Therefore, this cohort study aimed to (1) explore the association between pet ownership and the rate of cognitive decline; (2) evaluate the interaction between pet ownership and living alone; and (3) evaluate the extent to which pet ownership mitigates the association between living alone and the rate of cognitive decline in older adults.

Importance  

It is still unclear whether pet ownership is associated with cognitive decline and to what extent pet ownership mitigates the association between living alone and cognitive decline.

Aim  

To explore the association between pet ownership and cognitive decline, the interaction between pet ownership and living alone, and the extent to which pet ownership mitigates the association between living alone and cognitive decline in older adults.

Design, environment and participants  

This cohort study used data from waves 5 (June 2010 to July 2011) to 9 (June 2018 to July 2019) in the English Longitudinal Study of Aging. Participants included adults aged 50 years and older. Data was analyzed from April 1 to June 30, 2023.

Exhibitions  

Have a pet and live alone in wave 5.

Main results and measures  

In waves 5 to 9, verbal memory and verbal fluency were assessed, and composite verbal cognition was additionally calculated.

Results  

Of the 7,945 participants included, the mean (SD) age was 66.3 (8.8) years and 4,446 (56.0%) were women. Pet ownership was associated with slower rates of decline in composite verbal cognition (β = 0.008 [95% CI, 0.002-0.014] SD/year), verbal memory (β = 0.006 [95% CI, 0.001-0.012 ] SD/year) and verbal fluency (β = 0.007 [95% CI, 0.001-0.013] SD/year).

Three-way interaction tests showed that living alone was a significant modifier in all 3 associations.

Stratified analyzes showed that pet ownership was associated with slower rates of decline in composite verbal cognition (β = 0.023 [95% CI, 0.011-0.035] SD/year), verbal memory (β = 0.021 [95% CI, 0.011-0.035] SD/year), 95%, 0.008-0.034] SD/year) and verbal fluency (β = 0.018 [95% CI, 0.005-0.030] SD/year) among people living alone, but not among those living with others.

Joint association analyzes showed no significant differences in rates of decline in composite verbal cognition, verbal memory, or verbal fluency between pet owners living alone and pet owners living with others.

Figure: Estimated z-scores were calculated in SD units. Covariates were established with the following values: 65 years of age, female, white race, high educational level, retired, third wealth quintile, living alone, social isolation score of 1, currently not smoking, alcohol consumption less than one once a week, moderate physical activity, good self-assessed general health and no depressive symptoms, hypertension, diabetes or cardiovascular diseases.