For older adults living alone, owning a pet is associated with a slower rate of cognitive decline. However, pet ownership does not affect cognitive decline in older people who live with others.
This research used data from the English Longitudinal Study of Ageing (ELSA), a nationally representative cohort in England, and adopted a prospective cohort study design to assess cognitive function over time. Undertaken by a team based at Sun Yat-sen University in China, the research investigated the association between pet ownership and cognitive decline among adults aged 50 and older, with a specific focus on individuals who lived alone. Recognising the increasing prevalence of cognitive decline and dementia in the ageing population, the study aimed to identify potential modifiable risk factors, focusing on the role of pet ownership.
ELSA is an ongoing, prospective, and nationally representative cohort that has collected data since 2002, following participants biennially. The study utilises information from wave 5 as the baseline for assessing pet ownership, living arrangements, and potential covariates. Cognitive function is evaluated over subsequent waves (waves 5 to 9) to observe changes over time.
In wave 5, participants were asked, “Do you keep any household pets inside your house/flat?” The response options were binary: yes or no.
Living arrangements were determined based on the number of residents recorded in each household during wave 5. If only one household member (i.e., the participant) was recorded, they were classified as living alone; otherwise, they were considered to be living with others.
Cognitive function was assessed using verbal memory and verbal fluency tests in waves 5 to 9. These results were then used to calculate composite verbal cognition scores. The scores were standardised to allow for direct comparisons across different cognitive domains.
Various potential covariates were assessed in wave 5, including demographic factors (age, sex, race/ethnicity), socioeconomic status (educational level, employment status, wealth), health-related factors (smoking status, alcohol consumption, physical activity, self-rated general health, depressive symptoms, diabetes, hypertension, cardiovascular disease), and social factors (social isolation).
The key findings of the research showed that pet ownership is associated with a slower rate of cognitive decline in verbal memory, verbal fluency, and composite verbal cognition among older adults. Moreover, living alone significantly moderates the association between pet ownership and cognitive decline. Pet owners exhibited slower rates of cognitive decline when living alone, compared to non-pet owners who experienced accelerated cognitive decline when living alone. Furthermore, pet owners who lived alone showed rates of cognitive decline that were similar to pet owners who lived with others. This means that pet ownership completely offset the faster rates of cognitive decline associated with living alone, providing the same benefits as living with other people.
Longitudinal data allow the exploration of temporal relationships, providing insights into how pet ownership correlates with cognitive decline over time. While not definitive, longitudinal population studies offer a platform to explore potential causal relationships between pet ownership and cognitive decline, enabling researchers to assess whether one factor precedes the other. Longitudinal data capture dynamic changes, such as variations in pet ownership and living arrangements over time, offering a more nuanced understanding of their impact on cognitive function.
The study acknowledges attrition rates over the follow-up waves, which may introduce biases. However, the authors conducted sensitivity analyses to address potential issues related to missing data. The focus on verbal memory and verbal fluency, while relevant, provides only a partial assessment of cognitive function. A more comprehensive evaluation of various cognitive domains would enhance the study’s scope. Furthermore, detailed research into the impact of different types of pet (e.g., cat, fish, dog) on cognitive decline would be valuable.
Longitudinal studies are susceptible to unmeasured confounding factors that may influence the observed associations. In this study, the potential influence of factors like the APOE genotype is acknowledged.
The research has notable implications for policy and practice. For example, the findings suggest that promoting pet ownership, especially among older adults living alone, could be considered as a public health intervention to mitigate cognitive decline. Policymakers and healthcare practitioners should recognise the potential benefits of pet ownership in the context of cognitive health, particularly when addressing the needs of individuals living alone.
Whilst the study highlights the need for randomised clinical trials to further investigate the causal relationship between pet ownership and cognitive decline, it advocates for interventions promoting pet ownership to support healthy ageing.
In conclusion, this research contributes valuable insights into the association between pet ownership, living alone, and cognitive decline among older adults. The longitudinal approach enhances our understanding of the temporal dynamics involved. The findings also hold implications for shaping policies and interventions aimed at promoting cognitive health in ageing populations.
Kaye, N. (2024). Research Case Studies: Pet ownership, living alone & cognitive decline among older adults. CLOSER Learning Hub, London, UK: CLOSER.