Loneliness, Not Social Support, Is Associated with Cognitive Decline and Dementia Across Two Longitudinal Population-Based Cohorts

The effect of social exclusion on the cognitive health of middle-aged and older adults: A systematic review

This systematic review aimed to evaluate the independent and joint effects of social exclusion in three specific domains-economic, social relations, and civic participation-on the cognitive health of middle-aged and older adults. Longitudinal studies from January 2000 to October 2023 were identified via Web of Science, Scopus, and PubMed, with sixty-five studies meeting inclusion criteria. The quality of the studies was assessed with Newcastle-Otawa Scale. Analysis revealed a strong association between economic exclusion and cognitive decline, with most studies indicating a significant negative impact. Ten studies found a positive link between volunteering and cognitive health for civic participation, while eight did not, showing mixed evidence. In social relations, most studies connected loneliness, social isolation, smaller social networks, reduced contact with family and friends, lower engagement in activities, and negative social interactions with cognitive decline. Notably, one study found that older adults experiencing social exclusion in multiple domains simultaneously face even greater cognitive decline. In summary, this review shows that social exclusion in economic, social relations, and civic participation and all together domains is associated with greater cognitive decline in older adults.

Understanding loneliness after widowhood: The role of social isolation, social support, self-efficacy, and health-related factors

BACKGROUND

Widowhood negatively affects trajectories of social isolation and loneliness. Given the inevitability of spousal bereavement for many, further investigation into potential modifiers of bereavement-related loneliness is warranted.

AIM

To examine the moderating effects of social isolation, social support, sociodemographic, self-efficacy, health, and quality of life factors on changes in loneliness before and after widowhood.

METHODS

We analysed 19 waves of data from the Household, Income and Labour Dynamics in Australia (HILDA) Survey, comprising 749 widowed and 8,418 married individuals (comparison). Coarsened exact matching weights were applied, controlling for age and time trends. Local polynomial smoothed plots illustrated social health trajectories from three years before to three years after spousal death. All analyses were gender-stratified.

RESULTS

Low social isolation and higher social support did not prevent increased loneliness following widowhood. Men in major cities were less likely to experience reductions in social isolation during bereavement, despite being less socially-isolated at baseline than men in regional/remote areas. The bereavement-loneliness relationship was consistent across all subgroups. For men, this relationship was weakened by older age and being born in a non-English-speaking country, but strengthened by poverty and living in a regional/remote areas. For women, it was weakened by older age, and strengthened by factors such as being born in a non-English-speaking country, poverty, employment or volunteering, and having a long-term mental health condition.

CONCLUSION

Loneliness is a common and potentially unavoidable experience during widowhood, highlighting the importance of screening by healthcare workers to improve wellbeing and prevent future mental health issues.

Impact of social wellbeing on tooth loss and cognition: A scoping review

OBJECTIVE

The proposed explanations for the association between tooth loss and cognitive function have largely focused on systemic inflammation, mechanoreceptor feedback, and nutritive deficiencies. However, the role of social wellbeing in this relationship remains unknown. The aim of this scoping review is to explore the pathways linking different aspects of social function, collectively grouped under the umbrella of social wellbeing, to tooth loss and cognitive impairment.

DATA AND SOURCES

An electronic database search was performed in PubMed, Scopus, and Embase. Reference lists of relevant articles were also searched. Data on the associations between social wellbeing, cognitive function and tooth loss was charted in an extraction form and summarised qualitatively.

STUDY SELECTION

From the initial search of 3293 records, 71 studies were included in the present review. Forty-seven studies investigated the relationship between social wellbeing and cognition, 21 studies investigated the relationship between social wellbeing and tooth loss, and only 3 studies investigated all three variables.

CONCLUSION

This review demonstrates the need for further research on tooth loss, cognition and social wellbeing in tandem and describes potential psychological, biological, cognitive, and behavioural mechanisms interlinking these factors. While substantial evidence was found for the association between social relationships and cognition, fewer studies explored the potentially bidirectional relationship of social wellbeing and tooth loss.

CLINICAL SIGNIFICANCE

The implications of this review may guide clinicians to focus on the social consequences of tooth loss, which may have broader repercussions on cognitive health. The role of social support in helping older people cope with oral disease and the benefits of fostering positive lifestyle habits should not be underestimated.

A community-academic partnered approach to designing a Virtual Village to address the needs of older adults living with HIV

ABSTRACTMany older adults living with HIV face unique challenges, including comorbidities, loneliness, and isolation. This community-academic partnered study elicited viewpoints from older adults living with HIV about the characteristics of a digital environment ("Virtual Village") to combat against loneliness and isolation. We utilized Choice-Based Conjoint Analyses to determine preferred attributes of a Virtual Village. We also conducted focus groups and interviews with older adults living with HIV and used an iterative, data-driven approach to systematically identify emergent themes. Participants (N = 82) were aged 50-82 years and racially/ethnically diverse. The majority were men (78%), gay (66%), and lived with HIV for ≥15 years (83%). Cost was the factor that most drove participants' preference for joining a Virtual Village. Thematic concerns included lack of technological confidence, internet access, potential for harassment in digital environments, privacy, and preference for in-person interactions. Praises centered on convenience and making connections across geographic distances. Participants emphasized the need for purposive strategies to form a cohesive and supportive community for older adults living with HIV. A moderated environment was recommneded to create a safe, structured, and comfortable digital environment for older adults living with HIV. A Virtual Village should be viewed as a bridge to in-person interactions.

A Meta-analysis of Loneliness and Risk of Dementia using Longitudinal Data from >600,000 Individuals

Loneliness is one critical risk factor for cognitive health. Combining data from ongoing aging studies and the published literature, we provided the largest meta-analysis on the association between loneliness and dementia (k = 21 samples, N = 608,561) and cognitive impairment (k = 16, N = 103,387). Loneliness increased risk for all-cause dementia (HR = 1.306, 95% CI [1.197,1.426]), Alzheimer's disease (HR = 1.393, 95% CI [1.290,1.504]; k = 5), vascular dementia (HR = 1.735, 95% CI [1.483,2.029]; k = 3), and cognitive impairment (HR = 1.150, 95% CI [1.113,1.189]). The associations persisted when models controlled for depression, social isolation, and/or other modifiable risk factors for dementia. The large heterogeneity across studies was partly due to differences in loneliness measures and ascertainment of cognitive status. Results underscored the importance to further examine type/sources of loneliness and cognitive symptoms to develop effective interventions that reduce the risk of dementia.

Dementia and Cognitive Decline: A HEALM Approach

Dementia and cognitive decline pose significant global public health challenges, with prevalence expected to rise in the coming decades. Lifestyle medicine offers a promising approach to mitigating cognitive issues through six key interventions: diet, physical activity, restorative sleep, social connections, stress management, and avoiding risky substances. Traditional methods like randomized controlled trials (RCTs) have limitations in capturing the long-term impacts of these interventions. To overcome these challenges, the American College of Lifestyle Medicine (ACLM) and the True Health Initiative (THI) developed the Hierarchies of Evidence Applied to Lifestyle Medicine (HEALM) framework, informed by the Evidence Threshold Pathway Mapping (ETPM) approach. This framework integrates diverse evidence sources to assess intervention effects over time. Applying HEALM, this review evaluates lifestyle factors' impact on dementia and cognitive decline. It finds strong evidence supporting plant-based nutrition, physical activity, restorative sleep, and avoiding risky substances in promoting cognitive health. Social connections may mitigate cognitive decline, while stress management requires further investigation due to inconclusive findings. Integrating these findings into public health strategies could effectively address the growing dementia burden and enhance overall well-being in aging populations, underscoring the need for continued research in cognitive health.

Association of Loneliness with Functional and Cognitive Status in Minor and Major Neurocognitive Disorders

BACKGROUND

Neurocognitive disorders (NCDs) have a variable decline in cognitive function, while loneliness was associated with cognitive impairment and increased dementia risk. In the present study, we examined the associations of loneliness with functional and cognitive status in patients with minor (mild cognitive impairment) and major NCDs (dementia).

METHODS

We diagnosed mild NCD (n = 42) and major NCD (n = 164) through DSM-5 criteria on 206 participants aged > 65 years using the UCLA 3-Item Loneliness Scale (UCLA-3) to evaluate loneliness, the activities of daily living (ADL) and the instrumental activities of daily living (IADL) scales to measure functional status, and Mini-Mental State Examination (MMSE) to assess cognitive functions.

RESULTS

In a multivariate regression model, the effect of loneliness on cognitive functions was negative in major (β = -1.05, p < 0.0001) and minor NCD (β = -0.06, p < 0.01). In the fully adjusted multivariate regression model (sex-age-education-multimorbidity-depressive symptoms-antidementia drug treatment), the effect of loneliness remained negative for major NCD and became positive for minor NCD (β = 0.09, p < 0.001). The effect of loneliness on IADL (β = -0.26, p < 0.0001) and ADL (β = -0.24, p < 0.001) showed a negative effect for major NCD across the different models, while for minor NCD, the effect was positive (IADL: β = 0.26, p < 0.0001; ADL: β = 0.05, p = 0.01). Minor NCD displayed different levels of MMSE (β = 6.68, p < 0.001) but not ADL or IADL, compared to major NCD for the same levels of loneliness. MANOVA pill test suggested a statistically significant and different interactive effect of loneliness on functional and cognitive variables between minor and major NCDs.

CONCLUSIONS

We confirmed the relationships between loneliness and cognitive and functional status in major NCD, observing a novel trend in minor NCD.

Social health markers in the context of cognitive decline and dementia: an international qualitative study

Background

Social health in the context of dementia has recently gained interest. The development of a social health conceptual framework at the individual and social environmental levels, has revealed a critical need for a further exploration of social health markers that can be used in the development of dementia intervention and to construct social health measures.

Objective

To identify social health markers in the context of dementia.

Method

This international qualitative study included six countries: Australia, Germany, Indonesia, Italy, Poland, and the Netherlands. Using purposive sampling, three to five cases per country were recruited to the study, with each case consisting of a person living with dementia, a primary informal caregiver, an active network member, and a health care professional involved in the care of the person with dementia. In-depth interviews, using an agreed topic guide, and content analysis were conducted to identify known and new social health markers. The codes were then categorized against our conceptual framework of social health.

Results

Sixty-seven participants were interviewed. We identified various social health markers, ranging from those that are commonly used in epidemiological studies such as loneliness to novel markers of social health at the individual and the social environmental level. Examples of novel individual-level markers were efforts to comply with social norms and making own choices in, for example, keeping contact or refusing support. At a social environmental level, examples of novel markers were proximity (physical distance) and the function of the social network of helping the person maintaining dignity.

Conclusions

The current study identified both well-known and novel social health markers in the context of dementia, mapped to the social health framework we developed. Future research should focus on translating these markers into validated measures and on developing social health focused interventions for persons with dementia.

Sex-differences in the association of social health and marital status with blood-based immune and neurodegeneration markers in a cohort of community-dwelling older adults

BACKGROUND

The immune system has been proposed to play a role in the link between social health and all-cause dementia risk. We explored cross-sectional and longitudinal associations between social health, immune system balance and plasma neurodegeneration markers in community-dwelling older adults, and explored whether the balance between innate and adaptive immunity mediates associations between social health and both cognition and total brain volume.

METHODS

Social health markers (social support, marital status, loneliness) were measured in the Rotterdam Study between 2002-2008. Immune system cell counts and balance were assessed repeatedly from 2002 to 2016 using white blood-cell-based indices and individual counts (granulocyte-to-lymphocyte ratio (GLR), platelet-to-lymphocyte ratio (PLR), and systemic immune-inflammation index (SII)). Plasma neurodegeneration biomarkers (amyloid-β40, amyloid-β42, total tau and neurofilament light chain) were measured once from blood samples collected between 2002-2008. Global cognitive function and total brain volume (MRI) were measured at the follow-up visit between 2009-2014. We used linear mixed models to study longitudinal associations and performed causal mediation analyses.

RESULTS

In 8374 adults (mean age 65.7, 57 % female), never married participants (n = 394) had higher GLR, PLR and SII compared to married peers at baseline and during follow-up, indicating imbalance towards innate immunity. Being never married was associated with higher plasma amyloid-β40, and being widowed or divorced with higher plasma total tau levels at baseline. Widowed or divorced males, but not females, had higher GLR, PLR and SII at baseline. Higher social support was associated with lower PLR in females, but higher PLR in males. Loneliness was not associated with any of the immune system balance ratios. Never married males had higher levels of all plasma neurodegeneration markers at baseline. Immune system balance did not mediate associations between social health and cognition or total brain volume, but does interact with marital status.

CONCLUSION

This study indicates that marital status is associated with blood-based immune system markers toward innate immunity and higher levels of plasma neurodegeneration markers. This is particularly evident for never married or previously married male older adults compared to married or female peers.

A translational neuroscience perspective on loneliness: Narrative review focusing on social interaction, illness and oxytocin

This review addresses key findings on loneliness from the social, neurobiological and clinical fields. From a translational perspective, results from studies in humans and animals are included, with a focus on social interaction, mental and physical illness and the role of oxytocin in loneliness. In terms of social interactions, lonely individuals tend to exhibit a range of abnormal behaviors based on dysfunctional social cognitions that make it difficult for them to form meaningful relationships. Neurobiologically, a link has been established between loneliness and the hypothalamic peptide hormone oxytocin. Since social interactions and especially social touch regulate oxytocin signaling, lonely individuals may have an oxytocin imbalance, which in turn affects their health and well-being. Clinically, loneliness is a predictor of physical and mental illness and leads to increased morbidity and mortality. There is evidence that psychopathology is both a cause and a consequence of loneliness. The final section of this review summarizes the findings from social, neurobiological and clinical perspectives to present a new model of the complex construct of loneliness.

Gender-specific analysis of social connection patterns and risk of dementia in community-dwelling older people

INTRODUCTION

Poor social connection is considered a risk factor for dementia. Since socializing behaviors may cluster together or act compensatorily, we aimed to investigate social connection patterns and their association with dementia, for men and women separately.

METHODS

A total of 12,896 community-dwelling older adults (mean ± SD age: 75.2 ± 4.3 years, 54% women) without major cognitive impairment were included. Latent class analysis was conducted using 24 baseline social connection indicators. Cox proportional hazards regression was used to estimate the association between latent classes and incident dementia over 12 (median: 8.4) years follow-up.

RESULTS

Three distinct classes were identified in both genders: strong social connections with an intermediate friend-relative network (Class 1: men, 43.8%; women, 37.9%), weak social connections (Class 2: men, 29.6%; women, 27.4%), and strong social connections with a larger friend-relative network (Class 3: men, 26.6%; women, 34.7%). Compared to Class 1, men in Class 2 (HR: 1.38, 95% CI: 1.08-1.77) and women in Class 3 (HR: 1.27, 95% CI: 1.01-1.60) had an increased risk of dementia.

DISCUSSION

Dementia risk varies with different social connection patterns among older men and women.

HIGHLIGHTS

Three distinct social connection patterns were identified based on 24 indicators. These patterns were related to dementia risk differently in men and women. In men, a weak social connection pattern was associated with a higher dementia risk. In women, a strong social connection with a relatively larger friend-relative network was associated with a greater dementia risk.

Community support, social isolation and older adults' life satisfaction: evidence from a national survey in China

OBJECTIVES

Despite the recognized importance of community social service and community built facility for enhancing older adults' life satisfaction, the mechanisms underlying their relationship have not been thoroughly examined. This study aims to complement the existing knowledge by investigating the mediating role of social disconnectedness and loneliness in the association between community support and life satisfaction among older adults.

METHODS

Using data from the 2018 China Longitudinal Aging Social Survey, the study analyzes responses from 9,874 Chinese older adults (mean age = 71.30 years, SD = 7.30). We conducted descriptive statistics and Pearson's correlation to explore the variables. This study also used Mplus 8.0 to conduct a path analysis model that evaluated both the direct and indirect effects of community social service and built facility on life satisfaction. Social disconnectedness and loneliness were included as mediating variables in this model.

RESULTS

The present study results show that both community social service and community built facility are positively associated with life satisfaction among older adults, and community social service is more imporatant for enhancing the life satisfaction. In addition, these associations are mediated by social disconnectedness and loneliness.

CONCLUSION

Our research suggests that strengthening community social service programs and improving the built environment can reduce social disconnectedness and loneliness among older adults, ultimately enhancing their life satisfaction. Specifically, policymakers can invest in targeted interventions to enhance social connectedness and reduce loneliness, with the goal of improving the overall well-being of older adults.

Contributions of loneliness to cognitive impairment and dementia in older adults are independent of other risk factors and Alzheimer's pathology: a narrative review

Loneliness significantly contributes to cognitive impairment and dementia in older adults. Loneliness is a distressing feeling resulting from a perceived lack of social connection (i.e., a discrepancy between desired and actual social relationships), while social isolation is a related term that can be defined by number and type of social relationships. Importantly, loneliness is distinct from social isolation in that it is associated with a distressing self-perception. The primary focus of this narrative review is the impact of chronic loneliness on cognitive impairment and dementia among older adults. Loneliness has a significant association with many factors that are related to worse cognition, and therefore we include discussion on health, mental health, as well as the physiological effects of loneliness, neuropathology, and potential treatments. Loneliness has been shown to be related to development of dementia with a hazard ratio (HR) risk comparable to having a single APOE4 gene. The relationship of dementia to loneliness appears to be at least partially independent of other known dementia risk factors that are possibly associated with loneliness, such as depression, educational status, social isolation, and physical activity. Episodic memory is not consistently impacted by loneliness, which would be more typically impaired if the mild cognitive impairment (MCI) or dementia was due to Alzheimer's disease (AD) pathology. In addition, the several longitudinal studies that included neuropathology showed no evidence for a relationship between loneliness and AD neuropathology. Loneliness may decrease resilience, or produce greater cognitive change associated with the same level of AD neuropathology. Intervention strategies to decrease loneliness in older adults have been developed but need to consider key treatment targets beyond social isolation. Loneliness needs to be assessed in all studies of cognitive decline in elders, since it significantly contributes to the variance of cognitive function. It will be useful to better define the underlying mechanism of loneliness effects on cognition to determine if it is similar to other psychological factors related to excessive stress reactivity, such as neuroticism or even depression, which are also associated with cognitive decline. It is important from a health perspective to develop better strategies to decrease loneliness in older adults.

Loneliness, Dementia Status, and Their Association with All-Cause Mortality Among Older US Adults

Background

Loneliness, dementia, and mortality are interconnected.

Objective

We aimed at understanding mediating pathways and interactions between loneliness and dementia in relation to mortality risk.

Methods

The study tested bi-directional relationships between dementia, loneliness, and mortality, by examining both interactions and mediating effects in a large sample of older US adults participating in the nationally representative Health and Retirement Study. Out of≤6,468 older participants selected in 2010, with mean baseline age of 78.3 years and a follow-up time up to the end of 2020, 3,298 died at a rate of 64 per 1,000 person-years (P-Y). Cox proportional hazards and four-way decomposition models were used.

Results

Algorithmically defined dementia status (yes versus no) was consistently linked with a more than two-fold increase in mortality risk. Dementia status and Ln(odds of dementia) were strongly related with mortality risk across tertiles of loneliness score. Loneliness z-score was also linked to an elevated risk of all-cause mortality regardless of age, sex, or race or ethnicity, and its total effect (TE) on mortality was partially mediated by Ln(odds of dementia), z-scored, (≤40% of the TE was a pure indirect effect). Conversely, a small proportion (<5%) of the TE of Ln(odds of dementia), z-scored, on mortality risk was explained by the loneliness z-score.

Conclusions

In sum, dementia was positively associated with all-cause mortality risk, in similar fashion across loneliness score tertiles, while loneliness was associated with mortality risk. TE of loneliness on mortality risk was partially mediated by dementia odds in reduced models.

Adverse events in older adults and the risk of dementia and cognitive decline

Background

Increasing evidence suggests that stress could be a risk factor for dementia but this might vary by gender. This study investigated whether adverse life events were associated with cognitive decline and dementia in later-life, separately in men and women.

Methods

Participants were 12,789 community-dwelling Australians aged ≥ 70 years. Ten common adverse events in later-life were self-reported. Cognitive decline was defined as a 1.5 SD decline from participants' baseline score in tests of global cognition, psychomotor speed, episodic memory, and executive functioning, which were assessed regularly over a maximum of 10.3 years. Dementia was diagnosed according to DSM-IV criteria.

Results

An increased risk of dementia was observed in participants who experienced the death of a spouse/partner (HR: 1.72, 95% CI: 1.17 - 2.52) and for individuals who experienced major financial problems (HR: 1.53, 95% CI: 1.05 - 2.23). The latter also increased the risk of cognitive decline in men specifically (HR: 1.43, 95% CI: 1.10 - 1.86). In contrast, some events for women were associated with a reduced risk of dementia (e.g. close family or friends lost their job/retired (HR: 0.62, 95% CI: 0.40-0.95)).

Limitations

Events including major money problems may result from prodromal dementia symptoms, thus reverse causation needs to be considered.

Conclusions

Adverse life events may influence dementia risk in older adults, but associations vary depending on the nature of the event, and across genders. These findings support the need for early interventions in older people who have experienced adversities, particularly for the death of a loved one.

The Impact of Loneliness and Social Isolation on Cognitive Aging: A Narrative Review

Social concepts such as loneliness and social isolation are fairly new factors that have been recently gaining attention as to their involvement in changes in cognitive function and association with dementia. The primary aim of this narrative review was to describe the current understanding of how loneliness and social isolation influence cognitive aging and how they are linked to dementia. Studies have shown that there is an association between loneliness, social isolation, and reduced cognitive function, in older adults, across multiple cognitive domains, as well as a heightened risk of dementia. Numerous changes to underlying neural biomechanisms including cortisol secretion and brain volume alterations (e.g., white/grey matter, hippocampus) may contribute to these relationships. However, due to poor quality research, mixed and inconclusive findings, and issues accurately defining and measuring loneliness and social isolation, more consistent high-quality interventions are needed to determine whether studies addressing loneliness and social isolation can impact longer term risk of dementia. This is especially important given the long-term impact of the COVID-19 pandemic on social isolation in older people is yet to be fully understood.

Social participation and risk of developing dementia

The increasing number of people with dementia globally illustrates the urgent need to reduce dementia's scale and impact. Lifetime social participation may affect dementia risk by increasing cognitive reserve, and through brain maintenance by reducing stress and improving cerebrovascular health. It may therefore have important implications for individual behavior and public health policy aimed at reducing dementia burden. Observational study evidence indicates that greater social participation in midlife and late life is associated with 30-50% lower subsequent dementia risk, although some of this may not be causal. Social participation interventions have led to improved cognition but, partly due to short follow-up and small numbers of participants, no reduction in risk of dementia. We summarize the evidence linking social participation with dementia, discuss potential mechanisms by which social participation is likely to reduce and mitigate the impact of neuropathology in the brain, and consider the implications for future clinical and policy dementia prevention interventions.

Race and Apolipoprotein E-e4 Allele Status Differences in the Association Between Loneliness and Cognitive Decline

OBJECTIVE

This study aimed to examine race and apolipoprotein E-e4 allele (APOE-e4) status differences in the longitudinal associations between loneliness and cognitive decline.

METHODS

The study sample is composed of participants ( N = 7696, 64% Black participants and 36% White participants) from the Chicago Health and Aging Project, a population-based cohort study. Mixed-effects regression models were conducted to examine the longitudinal associations between loneliness on global cognitive function and individual tests of cognitive function. Models were also stratified by race and APOE-e4.

RESULTS

A greater percentage of Black participants (17%) reported loneliness at baseline visit compared with White participants (12%). Black and White participants who were lonely individuals had a similar rate of decline in global cognitive function at 0.075 (95% confidence interval [CI] = -0.082 to -0.068) standard deviation unit (SDU) per year for Black participants and at 0.075 (95% CI = -0.086 to -0.063) SDU per year for White participants. Lonely participants with APOE-e4 had a higher rate of global cognitive decline at -0.102 (95% CI = -0.115 to -0.088) SDU per year than for lonely participants without APOE-e4 at -0.052 (95% CI = -0.059 to -0.045) SDU per year.

CONCLUSIONS

The burden of loneliness and its relation to cognitive decline is higher among participants with APOE-e4 compared with those without APOE-e4. Loneliness is associated with cognitive decline in both Black and White participants.

The relationship between social isolation, social support, and loneliness with cardiovascular disease and shared risk factors: A narrative review

BACKGROUND

Cardiovascular disease (CVD) is the greatest contributor to global morbidity and mortality. Poor social health plays a critical role in CVD incidence. Additionally, the relationship between social health and CVD may be mediated through CVD risk factors. However, the underlying mechanisms between social health and CVD are poorly understood. Certain social health constructs (social isolation, low social support and loneliness) have complicated the characterisation of a causal relationship between social health and CVD.

AIM

To provide an overview of the relationship between social health and CVD (and its shared risk factors).

METHOD

In this narrative review, we examined published literature on the relationship between three social health constructs (social isolation, social support, and loneliness) and CVD. Evidence was synthesised in a narrative format, focusing on the potential ways in which social health affects CVD, including shared risk factors.

RESULTS

The current literature highlights an established relationship between social health and CVD with a likelihood for bi-directionality. However, there is speculation and varied evidence regarding how these relationships may be mediated through CVD risk factors.

CONCLUSIONS

Social health can be considered an established risk factor for CVD. However, the potential bi-directional pathways of social health with CVD risk factors are less established. Further research is needed to understand whether targeting certain constructs of social health may directly improve the management of CVD risk factors. Given the health and economic burdens of poor social health and CVD, improvements to addressing or preventing these interrelated health conditions would have societal benefits.

Social Isolation and Social Support Influence Health Service Utilisation and Survival after a Cardiovascular Disease Event: A Systematic Review

Both cardiovascular disease (CVD) and social health carry high health and economic burdens. We undertook a systematic review to investigate the association between social isolation, low social support, and loneliness with health service utilisation and survival after a CVD event among people living in Australia and New Zealand. Four electronic databases were systematically searched for the period before June 2020. Two reviewers undertook the title/abstract screen. One reviewer undertook a full-text screen and data extraction. A second author checked data extraction. Of 756 records, 25 papers met our inclusion criteria. Included studies recruited 10-12,821 participants, aged 18-98 years, and the majority were males. Greater social support was consistently associated with better outcomes on four of the five themes (discharge destination, outpatient rehabilitation attendance, rehospitalisation and survival outcomes; no papers assessed the length of inpatient stay). Positive social health was consistently associated with better discharge designation to higher independent living. As partner status and living status did not align with social isolation and social support findings in this review, we recommend they not be used as social health proxies. Our systematic review demonstrates that social health is considered in cardiac care decisions and plays a role in how healthcare is being delivered (i.e., outpatient, rehabilitation, or nursing home). This likely contributes to our finding that lower social support is associated with high-intensity healthcare services, lower outpatient rehabilitation attendance, greater rehospitalisation and poorer survival. Given our evidence, the first step to improve cardiac outcomes is acknowledging that social health is part of the decision-making process. Incorporating a formal assessment of social support into healthcare management plans will likely improve cardiac outcomes and survival. Further research is required to assess if support person/s need to engage in the risk reduction behaviours themselves for outpatient rehabilitation to be effective. Further synthesis of the impact of social isolation and loneliness on health service utilisation and survival after a CVD event is required.

Socioeconomic, Behavioural, and Social Health Correlates of Optimism and Pessimism in Older Men and Women: A Cross-Sectional Study

BACKGROUND

Optimism is a disposition characterised by positive future expectancies, while pessimism is characterised by expecting the worst. High optimism and low pessimism promote the health of older adults and may potentiate full engagement in life. We identified socioeconomic, behavioural, and social factors associated with optimism and pessimism in older adults.

METHODS

Participants included 10,146 community-dwelling, apparently healthy Australian adults aged 70 years and over from the ASPREE Longitudinal Study of Older Persons (ALSOP). Optimism and pessimism were measured using the revised Life Orientation Test. Cross-sectional ordinal logistic regression was used to determine the socioeconomic, behavioural, and social health factors associated with optimism and pessimism.

RESULTS

Higher education, greater physical activity, lower loneliness, and volunteering were associated with higher optimism and lower pessimism. Low social support was associated with higher pessimism. Higher socioeconomic advantage, greater income, and living alone were associated with lower pessimism. Women were more optimistic and less pessimistic than men. The association of age, smoking status, and alcohol consumption with optimism and pessimism differed for men and women.

CONCLUSIONS

Factors associated with higher optimism and lower pessimism were also those demonstrated to support healthy ageing. Health-promotion action at the individual level (e.g., smoking cessation or regular physical activity), health professional level (e.g., social prescribing or improving access and quality of care for all older adults), and community level (e.g., opportunities for volunteer work or low-cost social activities for older adults) may improve optimism and reduce pessimism, possibly also promoting healthy ageing.

The impact of loneliness and social isolation on the development of cognitive decline and Alzheimer's Disease

Alzheimer's Disease (AD) is the leading cause of dementia, observed at a higher incidence in women compared with men. Treatments aimed at improving pathology in AD remain ineffective to stop disease progression. This makes the detection of the early intervention strategies to reduce future disease risk extremely important. Isolation and loneliness have been identified among the major risk factors for AD. The increasing prevalence of both loneliness and AD emphasizes the urgent need to understand this association to inform treatment. Here we present a comprehensive review of both clinical and preclinical studies that investigated loneliness and social isolation as risk factors for AD. We discuss that understanding the mechanisms of how loneliness exacerbates cognitive impairment and AD with a focus on sex differences will shed the light for the underlying mechanisms regarding loneliness as a risk factor for AD and to develop effective prevention or treatment strategies.

Association between social integration and risk of dementia: A systematic review and meta-analysis of longitudinal studies

BACKGROUND

Dementia is an emerging public health issue. Growing evidence emerged on the association between social integration and the risk of dementia. However, the magnitude of the association between different aspects of social integration and the risk of dementia is unclear.

METHODS

Five databases were systematically searched. Newcastle-Ottawa scale for assessing the quality of the reporting was used for quality appraisal. Longitudinal cohort studies examining the association between social integration and the risk of dementia were analyzed using random effects model. A series of sensitivity analyses was conducted to enhance the robustness of the findings.

RESULTS

Forty publications generated from 32 studies/databases were included. The meta-analysis showed that strong social engagement (overall RR = 0.81, 95% CI = 0.74-0.89, p < 0.001) and frequent social contact (overall RR = 0.86, 95% CI = 0.76-0.97, p = 0.018) were positively associated with decreased risk of dementia. The influence of social support (overall RR = 0.92, 95% CI = 0.80-1.06, p = 0.238) and close social contact (overall RR = 0.74, 95% CI = 0.48-1.13, p = 0.167) was not significant. Loneliness was significantly associated with an increased risk of dementia (overall RR = 1.42, 95% CI = 1.26-1.60, p < 0.001), whereas the influence of social isolation (overall RR = 1.58, 95% CI = 0.80-3.12, p = 0.192) was not significant. A larger social network size (RR = 0.75, 95% CI = 0.59-0.97, p = 0.028) was a promising influencing factor even though the number of studies was insufficient for a meta-analysis. However, the heterogeneity among studies was generally high even though sensitivity analysis was conducted.

CONCLUSIONS

Our findings reveal that high social engagement and frequent social contact are significantly associated with a lower risk of dementia, whereas loneliness is associated with a higher risk. The promising impact of large social network size is also identified. Substantial heterogeneity appeared in most of the analysis, making the inference tentative. Nevertheless, the sensitivity analysis provided valuable implications that enhancing social engagement and reducing loneliness may prevent or delay the onset of dementia among middle-aged and older adults.

Association of Social Support with Mild Cognitive Impairment and Dementia Among Older Women: The Women's Health Initiative Memory Study

BACKGROUND

Social support may be a modifiable risk factor for cognitive impairment. However, few long-term, large prospective studies have examined associations of various forms of social support with incident mild cognitive impairment (MCI) and dementia.

OBJECTIVE

To examine associations of perceived social support with incident MCI and dementia among community-dwelling older women.

METHODS

This prospective cohort study included 6,670 women from the Women's Health Initiative Memory Study who were cognitively unimpaired at enrollment. We used Cox proportional hazards models to assess associations between perceived social support with incident MCI, dementia, or either MCI/dementia during an average 10.7 (SD = 6.1)-year follow-up. Modelling was repeated for emotional/information support, affection support, tangible support, and positive social interaction subscales of social support.

RESULTS

Among 6,670 women (average age = 70 years [SD = 3.8]; 97.0% non-Hispanic/Latina; 89.8% White), greater perceived social support was associated with lower risk of MCI/dementia after adjustment for age, ethnicity, race, hormone therapy, education, income, diabetes, hypertension, and body mass index (Tertile [T]3 versus T1: HR = 0.85, 95% CI 0.74-0.99; ptrend = 0.08). Associations were significant for emotional/information support (T3 versus T1: HR = 0.84, 95% CI 0.72-0.97; ptrend = 0.04) and positive social interaction (T3 versus T1: HR = 0.85, 95% CI 0.73-0.99; ptrend = 0.06) subscales. Associations were attenuated and not significant after adjustment for depressive symptom severity.

OBJECTIVE

Perceived social support, emotional/information support, and positive social interaction were associated with incident MCI/dementia among older women. Results were not significant after adjustment for depressive symptom severity. Improving social support may reduce risk of MCI and dementia in older women.

Association between loneliness and its components and cognitive function among older Chinese adults living in nursing homes: A mediation of depressive symptoms, anxiety symptoms, and sleep disturbances

OBJECTIVE

This study aimed to investigate the associations between loneliness and its components and cognitive function among older Chinese adults living in nursing homes and to test whether depressive symptoms, anxiety symptoms, and sleep disturbances mediate these associations.

METHODS

The sample comprised 228 Chinese individuals aged ≥ 65 years living in nursing homes who were free of dementia and psychiatric or serious somatic diseases. Loneliness was evaluated using the UCLA Loneliness Scale. Global cognitive function was assessed using the Beijing version of the Montreal Cognitive Assessment. Multivariable linear regression analyses were performed to examine the associations between loneliness and its components and global cognitive function. A mediation analysis was used to test the potential mediating effects of depressive symptoms, anxiety symptoms, and sleep disturbances.

RESULTS

The mean (SD) age of the participants was 80.8 (6.3) years, and 58.3% were women. Compared with the lowest quartile of loneliness degree, the multivariable-adjusted beta coefficient (95% confidence interval [95% CI]) for the highest quartile was -1.32 (-2.61 to -0.02) (P for trend = 0.03). Loneliness components, personal feelings of isolation and the lack of relational connectedness but not the lack of collective connectedness, were also inversely associated with cognitive function. Significant indirect effects on cognitive function were observed for loneliness and its two components (personal feelings of isolation and the lack of relational connectedness) in mediating pathways via depressive symptoms, anxiety symptoms, and sleep disturbances (all p < 0.05).

CONCLUSIONS

A higher degree of loneliness and its two components, personal feelings of isolation and the lack of relational connectedness, are associated with worse cognitive function among Chinese residents in nursing homes. Depressive symptoms, anxiety symptoms, and sleep disturbances may at least partially mediate these associations.

Eight-Year Trajectories of Late-Life Loneliness and Incident Dementia: A Nationally Representative Cohort Study

OBJECTIVE

Some older adults with loneliness might have transient loneliness, followed by full remission, while others might have persistent loneliness. Such different courses might differ in predicting the risk of dementia, but most previous studies assessed short-term loneliness at a single time point, ignoring the long-term changes of loneliness. This study aimed to explore the association between 8-year trajectories of late-life loneliness and incident dementia.

METHODS

Data were from the English Longitudinal Study of Ageing (waves 2-9). This study included 6,722 older adults measured for loneliness greater than or equal to three times from wave 2 (2004-2005) to wave 6 (2012-2013) and free from dementia in wave 6. Loneliness was assessed using the short 1980 version of the University of California, Los Angeles Loneliness Scale. Group-based trajectory modeling was used to explore loneliness trajectories during waves 2-6. Cox proportional hazard models were used to investigate the association of loneliness trajectories with incident dementia during waves 6-9.

RESULTS

Five distinct loneliness trajectories were identified: long-term low, persistently decreasing, persistently increasing, long-term moderate, and long-term high. Compared with long-term low loneliness, the HRs (95% confidence intervals) for persistently decreasing, persistently increasing, long-term moderate, and long-term high loneliness were 1.29 (0.83-2.00), 1.55 (1.04-2.31), 1.56 (1.03-2.38), and 3.35 (1.89-5.91), respectively.

CONCLUSION

The elderly show distinct patterns of loneliness over time, which cannot be captured by a single assessment of loneliness. The elderly with long-term loneliness and persistently increasing loneliness might be the high-risk group for dementia. Further studies are needed to determine whether reducing loneliness can prevent dementia.

Association between loneliness and dementia risk: A systematic review and meta-analysis of cohort studies

Loneliness has been reported to be associated with an increased risk of dementia; however, the extent of this relationship remains controversial. This study aimed to assess the strength of the relationship between loneliness and dementia using a meta-analysis approach. PubMed, EMBASE, and China National Knowledge Internet databases were systematically searched for potentially included studies from inception up to 17 February 2022. A meta-analysis was performed using a random-effects model to assess pooled relative risks (RRs) and 95% confidence intervals (CIs). A literature search identified 16 cohort studies (published in 15 articles), among which 4,625 dementia cases and 62,345 individuals were selected for further meta-analysis. Loneliness was associated with an increased risk of Alzheimer's disease (AD) (RR: 1.72, 95% CI: 1.32-2.23; P < 0.001) and dementia (RR: 1.23, 95% CI: 1.16-1.31; P < 0.00001). However, no significant association between loneliness and risk of mild cognitive impairment (MCI) (RR: 1.34, 95% CI: 0.97-1.87; P = 0.080) or vascular dementia (VaD) (RR: 1.01, 95% CI: 0.51-1.99; P = 0.973) was observed. Results revealed that loneliness might increase the risk of Alzheimer's disease and dementia. Early interventions that limit loneliness may reduce risk of dementia and Alzheimer's disease.

Associations between social connections and cognition: a global collaborative individual participant data meta-analysis

BACKGROUND

Poor social connections (eg, small networks, infrequent interactions, and loneliness) are modifiable risk factors for cognitive decline. Existing meta-analyses are limited by reporting aggregate responses, a focus on global cognition, and combining social measures into single constructs. We aimed to investigate the association between social connection markers and the rate of annual change in cognition (ie, global and domain-specific), as well as sex differences, using an individual participant data meta-analysis.

METHODS

We harmonised data from 13 longitudinal cohort studies of ageing in North America, South America, Europe, Africa, Asia, and Australia. Studies were eligible for inclusion if they had baseline data for social connection markers and at least two waves of cognitive scores. Follow-up periods ranged from 0 years to 15 years across cohorts. We included participants with cognitive data for at least two waves and social connection data for at least one wave. We then identified and excluded people with dementia at baseline. Primary outcomes were annual rates of change in global cognition and cognitive domain scores over time until final follow-up within each cohort study analysed by use of an individual participant data meta-analysis. Linear mixed models within cohorts used baseline social connection markers as predictors of the primary outcomes. Effects were pooled in two stages using random-effects meta-analyses. We assessed the primary outcomes in the main (partially adjusted) and fully adjusted models. Partially adjusted models controlled for age, sex, and education; fully adjusted models additionally controlled for diabetes, hypertension, smoking, cardiovascular risk, and depression.

FINDINGS

Of the 40 006 participants in the 13 cohort studies, we excluded 1392 people with dementia at baseline. 38 614 individual participants were included in our analyses. For the main models, being in a relationship or married predicted slower global cognitive decline (b=0·010, 95% CI 0·000-0·019) than did being single or never married; living with others predicted slower global cognitive (b=0·007, 0·002-0·012), memory (b=0·017, 0·006-0·028), and language (b=0·008, 0·000-0·015) decline than did living alone; and weekly interactions with family and friends (b=0·016, 0·006-0·026) and weekly community group engagement (b=0·030, 0·007-0·052) predicted slower memory decline than did no interactions and no engagement. Never feeling lonely predicted slower global cognitive (b=0·047, 95% CI 0·018-0·075) and executive function (b=0·047, 0·017-0·077) decline than did often feeling lonely. Degree of social support, having a confidante, and relationship satisfaction did not predict cognitive decline across global cognition or cognitive domains. Heterogeneity was low (I2=0·00-15·11%) for all but two of the significant findings (association between slower memory decline and living with others [I2=58·33%] and community group engagement, I2=37·54-72·19%), suggesting robust results across studies.

INTERPRETATION

Good social connections (ie, living with others, weekly community group engagement, interacting weekly with family and friends, and never feeling lonely) are associated with slower cognitive decline.

FUNDING

EU Joint Programme-Neurodegenerative Disease Research grant, funded by the National Health and Medical Research Council Australia, and the US National Institute on Aging of the US National Institutes of Health.

Association of Low Emotional and Tangible Support With Risk of Dementia Among Adults 60 Years and Older in South Korea

IMPORTANCE

The association between social support and dementia risk has been debated. Most previous prospective studies have not differentiated the subtypes of social support.

OBJECTIVE

To examine whether the association between social support and risk of dementia differs by subtype of social support and by sex.

DESIGN, SETTING, AND PARTICIPANTS

This nationwide prospective cohort study included randomly sampled South Korean adults 60 years or older. The study was launched November 1, 2010, with follow-up every 2 years until November 30, 2020. The 5852 participants who completed the assessment for social support and were not diagnosed as having dementia, severe psychiatric disorders including major depressive disorder, or major neurological disorders at the baseline assessment were included in the analysis.

EXPOSURES

Geriatric psychiatrists administered the structured diagnostic interviews and physical examinations to every participant based on the Korean version of the Consortium to Establish a Registry for Alzheimer Disease (CERAD-K) Assessment Packet Clinical Assessment Battery.

MAIN OUTCOMES AND MEASURES

Baseline levels of emotional and tangible support using the Medical Outcomes Survey Social Support Survey.

RESULTS

Among the 5852 participants (mean [SD] age, 69.8 [6.6] years; 3315 women [56.6%]; mean [SD] follow-up duration, 5.9 [2.4] years), 237 (4.0%) had incident all-cause dementia and 160 (2.7%) had incident Alzheimer disease (AD) subtype of dementia. Compared with women who reported having emotional support, those with low emotional support had almost a 2-fold higher incidence of all-cause dementia (18.4 [95% CI, 13.6-23.2] vs 10.7 [95% CI, 9.0-12.5] per 1000 person-years) and AD (14.4 [95% CI, 10.2-18.6] vs 7.8 [95% CI, 6.3-9.3] per 1000 person-years). Adjusted Cox proportional hazard analysis revealed that low emotional support was associated with increased risk of all-cause dementia (hazard ratio, 1.61 [95% CI, 1.10-2.36]; P = .02) and AD (hazard ratio, 1.66 [95% CI, 1.07-2.57]; P = .02) only in women. Low tangible support was not associated with a risk of all-cause dementia or AD regardless of sex.

CONCLUSIONS AND RELEVANCE

The findings of this cohort study suggest that older women with low emotional support constitute a population at risk for dementia. The level of emotional support should be included in risk assessments of dementia.

Associations between loneliness and frailty among older adults: Evidence from the China Health and Retirement Longitudinal Study

Background

Previous studies have demonstrated the associations between loneliness and frailty in late life. However, there is a lack of consensus on the direction of the relationship. The present study aimed to examine the interdependencies between loneliness and frailty over time.

Methods

Data on participants aged 60 years old and above were collected from the 2011, 2013, and 2015 samples of the China Health and Retirement Longitudinal Study (CHARLS). Loneliness was measured by a single question from the Centre for Epidemiological Studies Depression scale, and frailty was assessed by the Physical Frailty Phenotype (PFP) scale. Cross-lagged panel models were utilized to examine the potential bidirectional relationship between loneliness and frailty.

Results

Reciprocal associations were found between loneliness and frailty. Furthermore, we found that baseline frailty and early change in frailty had a significant predictive effect on late change in loneliness. Higher baseline loneliness in older adults may create a potentially vicious cycle that influenced early change in frailty and continued to cause late change in loneliness.

Conclusion

A bidirectional relationship may exist between loneliness and frailty among older Chinese adults over 60 years old. Lonely older adults should be alerted to the potential self-reinforcing cycle of loneliness that affects their health.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12877-022-03044-0.

Social isolation, social support, and loneliness and their relationship with cognitive health and dementia

BACKGROUND

Poor social health is prevalent in older adults and may be associated with worse cognition, and increased dementia risk. The aim of this study was to determine whether social isolation, social support and loneliness are independently associated with cognitive function and incident dementia over 5 years in older adults, and to investigate potential gender differences.

METHODS

Participants were 11,498 community-dwelling relatively healthy Australians aged 70-94, in the ASPREE Longitudinal Study of Older Persons (ALSOP). Social isolation, social support, loneliness and cognitive function were assessed through self-report. Outcomes examined were cognitive decline (>1.5 SD decline in cognitive performance since baseline) and incident dementia (adjudicated according to DSM-IV criteria).

RESULTS

Most participants self-reported good social health (92%) with very few socially isolated (2%), with low social support (2%) or lonely (5%). Among women, social isolation and low social support were consistently associated with lower cognitive function (e.g., social support and cognition β = -1.17, p < 0.001). No consistent longitudinal associations were observed between baseline social health and cognitive decline (over median 3.1 years) or incident dementia (over median 4.4 years; social isolation: HR = 1.00, p = 0.99; low social support: HR = 1.79, p = 0.11; loneliness: HR = 0.72, p = 0.34 among women and men).

CONCLUSION

Our study provides evidence that social isolation and a low social support are associated with worse cognitive function in women, but not men. Social health did not predict incident cognitive decline or dementia, but we lacked power to stratify dementia analyses by gender.