Combined Impact of Social Isolation and Loneliness Found to Diminish Cognitive Health

In a recent study published in Archives of Gerontology and Geriatrics, researchers from Canada investigated the individual and combined effects of social isolation (SI) and loneliness (LON) on memory in middle-aged and older adults over six years.

They found that experiencing both SI and LON had the greatest negative impact on memory, followed by LON alone, SI alone, and neither condition, suggesting that addressing both factors together may improve memory outcomes in this population.

Study: Exploring the differential impacts of social isolation, loneliness, and their combination on the memory of an aging population: A 6-year longitudinal study of the CLSA. Image Credit: Perfect Wave/Shutterstock.com

Background

Memory involves encoding, storing, and retrieving information. Declines in memory, common in aging, can impact daily activities and may indicate neurocognitive disorders like Alzheimer's disease.

Over 55 million people globally have these disorders, with numbers expected to rise. Social isolation (SI) and loneliness (LON) are preventable factors that can worsen age-related memory loss. SI relates to structural social support deficiencies, while LON reflects subjective dissatisfaction with social connections. Both factors are distinct but linked to adverse health outcomes.

Existing studies mostly explore their impacts on global cognition or other cognitive domains, not memory. They often overlook the combined effect of SI and LON and focus on older adults, neglecting middle-aged populations.

The combined impact of SI and LON presents unique health risks, including cardiovascular disease and depression, particularly among older, widowed, lower-income females.

Comprehensive studies over longer periods are needed to understand these relationships better and develop effective interventions. Therefore, researchers in the present study aimed to fill this gap by examining the specific and combined effects of SI and LON on memory, especially in middle-aged and older adults, using a long-term, multidimensional approach.

About the study

Data were obtained from the Canadian Longitudinal Study on Aging (CLSA) Tracking Cohort, initially recruiting adults aged 45–85 years between 2011 and 2015, with follow-up data collected in 2015-2018 and 2018-2021. Participants were enrolled from the Canadian Community Health Survey and additional methods like mailouts and random digit dialling.

Exclusions included residents of First Nations reserves, the territories, long-term care institutions, full-time military members, non-permanent residents, and those judged cognitively impaired. The cohort was stratified by age, sex, province, education, and distance from study centers, providing data via computer-assisted telephone interviews.

A 5-point scale was used to measure SI and divided it into non-isolated and isolated categories. LON was assessed using a CES-D-10 question, divided into lonely and not-lonely categories. These measures were combined to form four groups: only socially isolated, only lonely, both isolated and lonely, and neither.

Memory was assessed using a modified Rey Auditory Verbal Learning Test (RAVLT), focusing on immediate and delayed recall to evaluate episodic and working memory.

Scores were standardized into z-scores for a cognitively healthy subset and combined for analysis. Covariates included sociodemographic attributes, functional ability, lifestyle variables, and chronic health conditions.

The analytical sample included 14,658 participants from the CLSA, and three sets of analyses were conducted. The primary analysis utilized a modified “all available data” (AADA) approach.

Two sensitivity analyses were performed: one with non-modified AADA and another using multiple imputations. Further, the statistical analysis involved descriptive assessments, mixed-effects regression, and assessment of clinical significance using Cohen's d.

Results and discussion

About 82.90% of participants were neither socially isolated nor lonely, with smaller proportions experiencing only SI (7.88%), only LON (7.98%), or both (1.23%). Most participants showed average memory scores across follow-up periods. Significant inverse associations were observed between SI/LON groups and memory, with the “neither” group scoring highest and the “both” group scoring lowest.

The “neither” group had better socioeconomic and health profiles. In the group with SI and LON, memory deterioration was observed over six years. Clinical significance was confirmed for the “both” and “only LON” groups, indicating negative associations with memory, but the “only SI” group showed no significant effects.

The study uniquely examines the combined effects of SI and LON on memory across middle-aged and older adults, using a comprehensive set of covariates and longitudinal data to capture changes over six years.

However, the sample may not represent the broader population due to healthier participants and potential biases in LON measurement, possibly underestimating the associations between SI, LON, and memory.

Conclusion

In conclusion, the study suggests that the combined experience of both SI and LON results in the most severe memory impairment, with LON having a stronger effect than SI, emphasizing the need for targeted interventions.

In the future, programs should address structural barriers for the combined group and provide tailored support for those experiencing only LON or SI.

Continuous monitoring of transitions among these categories is crucial as individuals face evolving challenges related to social engagement and cognitive health.