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.

The link between social and emotional isolation and dementia in older black and white Brazilians

OBJECTIVE

To examine the link between social and emotional isolation and likelihood of dementia among older black and white Brazilians.

DESIGN

Cross-sectional clinical-pathological cohort study.

SETTING

Medical center in Sao Paulo, Brazil.

PARTICIPANTS

As part of the Pathology, Alzheimer's and Related Dementias Study, we conducted uniform structured interviews with knowledgeable informants (72% children) of 1,493 older (age > 65) Brazilian decedents.

MEASUREMENTS

The interview included measures of social isolation (number of family and friends in at least monthly contact with decedent), emotional isolation (short form of UCLA Loneliness Scale), and major depression plus the informant portion of the Clinical Dementia Rating Scale to diagnose dementia and its precursor, mild cognitive impairment (MCI).

RESULTS

Decedents had a median social network size of 8.0 (interquartile range = 9.0) and a median loneliness score of 0.0 (interquartile range = 1.0). On the Clinical Dementia Rating Scale, 947 persons had no cognitive impairment, 122 had MCI, and 424 had dementia. In a logistic regression model adjusted for age, education, sex, and race, both smaller network size (odds ratio [OR] = 0.975; 95% confidence interval [CI]: 0.962, 0.989) and higher loneliness (OR = 1.145; 95% CI: 1.060, 1.237) were associated with higher likelihood of dementia. These associations persisted after controlling for depression (present in 10.4%) and did not vary by race. After controlling for depression, neither network size nor loneliness was related to MCI.

CONCLUSION

Social and emotional isolation are associated with higher likelihood of dementia in older black and white Brazilians.

Social health and subsequent cognitive functioning in people aged 50 years and older: examining the mediating roles of depressive symptoms and inflammatory biomarkers in two European longitudinal studies

BACKGROUND

Social health markers, including marital status, contact frequency, network size, and social support, have been shown to be associated with cognition. However, the mechanisms underlying these associations remain poorly understood. We investigated whether depressive symptoms and inflammation mediated associations between social health and subsequent cognition.

METHODS

In the English Longitudinal Study of Ageing (ELSA), a nationally representative longitudinal study in England, UK, we sampled 7136 individuals aged 50 years or older living in private households without dementia at baseline or at the intermediate mediator assessment timepoint, who had recorded information on at least one social health marker and potential mediator. We used four-way decomposition to examine to what extent depressive symptoms, C-reactive protein, and fibrinogen mediated associations between social health and subsequent standardised cognition (verbal fluency and delayed and immediate recall), including cognitive change, with slopes derived from multilevel models (12-year slope). We examined whether findings were replicated in the Swedish National Study on Aging and Care in Kungsholmen (SNAC-K), a population-based longitudinal study in Sweden, in a sample of 2604 individuals aged 60 years or older living at home or in institutions in Kungsholmen (central Stockholm) without dementia at baseline or at the intermediate mediator assessment timepoint (6-year slope). Social health exposures were assessed at baseline, potential mediators were assessed at an intermediate timepoint (wave 2 in ELSA and 6-year follow-up in SNAC-K); cognitive outcomes were assessed at a single timepoint (wave 3 in ELSA and 12-year follow-up in SNAC-K), and cognitive change (between waves 3 and 9 in ELSA and between 6-year and 12-year follow-ups in SNAC-K).

FINDINGS

The study sample included 7136 participants from ELSA, of whom 3962 (55·5%) were women and 6934 (97·2%) were White; the mean baseline age was 63·8 years (SD 9·4). Replication analyses included 2604 participants from SNAC-K, of whom 1604 (61·6%) were women (SNAC-K did not collect ethnicity data); the mean baseline age was 72·3 years (SD 10·1). In ELSA, we found indirect effects via depressive symptoms of network size, positive support, and less negative support on subsequent verbal fluency, and of positive support on subsequent immediate recall (pure indirect effect [PIE] 0·002 [95% CI 0·001-0·003]). Depressive symptoms also partially mediated associations between less negative support and slower decline in immediate recall (PIE 0·001 [0·000-0·002]) and in delayed recall (PIE 0·001 [0·000-0·002]), and between positive support and slower decline in immediate recall (PIE 0·001 [0·000-0·001]). We did not observe mediation by inflammatory biomarkers. Findings of mediation by depressive symptoms in the association between positive support and verbal fluency and between positive support and change in immediate recall were replicated in SNAC-K.

INTERPRETATION

The findings of this study provide new insights into mechanisms linking social health with cognition, suggesting that associations between interactional aspects of social health, especially social support, and cognition are partly underpinned by depressive symptoms.

FUNDING

EU Joint Programme-Neurodegenerative Disease Research (JPND) and Alzheimer's Society.

TRANSLATION

For the Swedish translation of the abstract see Supplementary Materials section.

Social Contagion and General Diffusion Models of Adolescent Religious Transitions: A Tutorial, and EMOSA Applications

Epidemic Models of the Onset of Social Activities (EMOSA) describe behaviors that spread through social networks. Two social influence methods are represented, social contagion (one-to-one spread) and general diffusion (spread through cultural channels). Past models explain problem behaviors-smoking, drinking, sexuality, and delinquency. We provide review, and a tutorial (including examples). Following, we present new EMOSA models explaining changes in adolescent and young adult religious participation. We fit the model to 10 years of data from the 1997 U.S. National Longitudinal Survey of Youth. Innovations include a three-stage bi-directional model, Bayesian Markov Chain Monte Carlo (MCMC) estimation, graphical innovations, and empirical validation. General diffusion dominated rapid reduction in church attendance during adolescence; both diffusion and social contagion explained church attendance stability in early adulthood.

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.

Social health, social reserve and dementia

PURPOSE OF REVIEW

There is increasing recognition of social health being protective against disease, including age-related cognitive decline and dementia. Many concepts around social health, reserve and connectedness are imprecise and without agreed definitions. The mechanisms by which social health is protective are not well understood.

RECENT FINDINGS

Several observational studies suggest that social participation and connectedness are protective against cognitive decline whereas loneliness is a risk factor for dementia. The possible mechanisms include effects on inflammatory process and immune function, reduced vascular disease risk, improved health behaviours, lower risk of depression, and increased cognitive reserve through cognitive stimulation and physical activity. Social networks have been shown to modify the relationship between Alzheimer's disease and cognitive impairment. The relationship of social networks is, however, reciprocal, with dementia leading to social loss, which in turn worsens cognitive decline. Social reserve is conceptualized as both brain processes underlying the ability and predisposition to form meaningful social ties, and their instantiation as an environmental resource in high-quality social networks.

SUMMARY

Consistent definitions of social health-related terms will lead to better understanding of their determinants so that tailored interventions can be developed to increase social reserve and improve social health of an individual.

Social networks and cognitive function in older adults: findings from the HAPIEE study

BACKGROUND

Social networks are associated with better cognitive health in older people, but the role of specific aspects of the social network remains unclear. This is especially the case in Central and Eastern Europe. This study examined associations between three aspects of the social network (network size of friends and relatives, contact frequency with friends and relatives, and social activity participation) with cognitive functions (verbal memory, learning ability, verbal fluency, processing speed, and global cognitive function) in older Czech, Polish, and Russian adults.

METHODS

Linear regression estimated associations between baseline social networks and cognitive domains measured at both baseline and follow-up (mean duration of follow-up, 3.5 ± 0.7 years) in 6691 participants (mean age, 62.2 ± 6.0 years; 53.7% women) from the Health, Alcohol and Psychosocial factors In Eastern Europe (HAPIEE) study.

RESULTS

Cross-sectional analyses, adjusted for country, age, and sex, showed positive associations of global cognitive function with social activity participation and network size of friends and relatives, but not with contact frequency in either network. Further adjustment for sociodemographic, behavioural, and health characteristics attenuated the associations with network size of relatives (P-trend = 0.074) but not with network size of friends (P-trend = 0.036) or social activities (P-trend< 0.001). In prospective analyses, network size and social activity participation were also linked with better cognition in simple models, but the associations were much stronger for social activities (P-trend< 0.001) than for network size of friends (P-trend = 0.095) and relatives (P-trend = 0.425). Adjustment for baseline cognition largely explained the prospective associations with network size of friends (P-trend = 0.787) and relatives (P-trend = 0.815), but it only slightly attenuated the association with social activities (P-trend< 0.001). The prospective effect of social activities was largely explained by sociodemographic, health behavioural, and health covariates (P-trend = 0.233). Analyses of specific cognitive domains generally replicated the cross-sectional and prospective findings for global cognitive function.

CONCLUSIONS

Older Central and Eastern European adults with larger social networks and greater social activities participation had better cognitive function, but these associations were stronger at baseline than over the short-term follow-up.

Behavioral and neural correlates of social network size: The unique and common contributions of face recognition and extraversion

OBJECTIVES

Humans are inherently social creatures and can gain advantages from larger network size. Researches have shown that different cognitive and personality factors may result in individual differences of social network size (SNS). Here, we focused on whether face recognition ability and extraversion were related to SNS and the neural basis underlying the relations.

METHODS

Behaviorally, we adopted the face-inversion task, NEO personality inventory, and computerized SNS test to explore the relationships between face recognition, extraversion, and SNS. Neurally, we used resting state functional magnetic resonance imaging and fractional amplitude of low-frequency fluctuation (fALFF) analysis method to investigate the neural correlates of SNS and then revealed whether face recognition and extraversion were related to SNS relevant brain regions.

RESULTS

We found that individuals with better face recognition ability and more extraverted personality had larger size of social network. In addition, we found that SNS was positively associated with the fALFF in the ventromedial prefrontal cortex (vmPFC), right superior temporal sulcus, and precuneus. Interestingly, the fALFF in the vmPFC significantly correlated with face recognition ability.

CONCLUSIONS

Our study suggests that both face recognition and extraversion may be important correlates of SNS, and the underlying spontaneous neural substrates are partially dissociable.

Bidirectional and dynamic relationships between social isolation and physical functioning among older adults: A cross-lagged panel model of US national survey data

BACKGROUND

Previous studies examining unidirectional relationships between social isolation and physical functioning amongst older adults may be biased due to reverse causality. This study leveraged data from a US national sample of older adults and a novel estimation method to identify bidirectional associations between these two phenomena and their associated temporal dynamics.

METHODS

The analyses were based on nine waves of panel data from a sample of adults aged 65+ years from the US National Health and Aging Trends Study (n=12,427 individuals) and a cross-lagged panel model. Social isolation was measured using the Social Isolation Index (SII) and physical functioning through the Short Physical Performance Battery (SPPB).

RESULTS

One SD increase in the SPPB was associated with a -0.013 SD decrease (95% CI: -0.023, -0.004) in the SII a year later, whereas one SD increase in the SII was associated with a larger -0.058 SD decrease (95% CI: -0.069, -0.046) in the SPPB a year later. The SII→SPPB effect lasted for ~5 years, whereas the SPPB→SII lasted for ~3 years.

CONCLUSIONS

This study confirmed the existence of statistically significant bidirectional associations between social isolation and physical functioning amongst older adults in the US, net of reverse causation. Since the effect of social isolation dominates, the findings indicate that public-health strategies to promote successful aging should prioritise interventions that enrich older adults' social networks. Further, the effect time horizons yielded by the model point to the optimal timing for the re-delivery of interventions.