Insight into Potential Mechanisms Linking Loneliness and Cognitive Decline: Commentary on "Health Factors as Potential Mediator the Longitudinal Effect of Loneliness on General Cognitive Ability"

Loneliness and global cognitive functioning in racially and ethnically diverse US midlife and older adults

Introduction

Few studies have examined the association of loneliness and cognitive functioning in the US. We used two common measures of loneliness and examined their association in a large sample of US Black, Latino, and White adults (ages ≥ 50).

Methods

We analyzed Wave 3 of the National Social Life, Health, and Aging Project (N = 2,757). We examined loneliness using one item from the CES-D and the Felt Loneliness Measure (NFLM); cognitive functioning was assessed using the Montreal Cognitive Assessment (MoCA) tool, where higher scores indicated better functioning. We used weighted ordinary least squares regressions to examine the effects of loneliness (CES-D loneliness and NFLM in separate models) on MoCA scores. In exploratory analyses, we examined if these relationships varied by race and ethnicity. We adjusted all models for sociodemographic and other salient factors (e.g., chronic disease, depressive symptoms, living alone).

Results

Mean age was 63.49 years, 52% were female, and 9% were Black and 6% Latino persons. Approximately 54% endorsed feeling lonely on at least one measure; 31% (CES-D) and 46% (NFLM). The relationship between loneliness measures was positive and significant, X 2 (1, N = 2,757) = 435.493 p < 0.001. However, only 40% of lonely individuals were identified as lonely on both assessments. CES-D loneliness was inversely (βˆ = -0.274, p = 0.032) associated with MoCA scores and this association did not vary by race and ethnicity. Greater NFLM loneliness was positively associated (βˆ = 0.445, p < 0.001) with higher MoCA scores for Latino participants only.

Discussion

Loneliness appears to be an important predictor of cognitive functioning. However, the association of loneliness and cognitive functioning varied when using the CES-D loneliness item or the NFLM. Future work is needed to understand how loneliness and its clinically relevant dimensions (social, emotional, existential, chronicity) relate to global and individual cognitive domains. Research is needed with racially and ethnically diverse midlife and older adults, particularly to understand our counterintuitive finding for Latino participants. Finally, findings also support the need for research on interventions to prevent cognitive decline targeting loneliness.

The role of quality of life data as an endpoint for collecting real-world evidence within geroscience clinical trials

With geroscience research evolving at a fast pace, the need arises for human randomized controlled trials to assess the efficacy of geroprotective interventions to prevent age-related adverse outcomes, disease, and mortality in normative aging cohorts. However, to confirm efficacy requires a long-term and costly approach as time to the event of morbidity and mortality can be decades. While this could be circumvented using sensitive biomarkers of aging, current molecular, physiological, and digital endpoints require further validation. In this review, we discuss how collecting real-world evidence (RWE) by obtaining health data that is amenable for collection from large heterogeneous populations in a real-world setting can help speed up validation of geroprotective interventions. Further, we propose inclusion of quality of life (QoL) data as a biomarker of aging and candidate endpoint for geroscience clinical trials to aid in distinguishing healthy from unhealthy aging. We highlight how QoL assays can aid in accelerating data collection in studies gathering RWE on the geroprotective effects of repurposed drugs to support utilization within healthy longevity medicine. Finally, we summarize key metrics to consider when implementing QoL assays in studies, and present the short-form 36 (SF-36) as the most well-suited candidate endpoint.

Investigating Biological Pathways Underpinning the Longitudinal Association Between Loneliness and Cognitive Impairment

BACKGROUND

Loneliness precedes the onset of cognitive impairment (CI) in older adults. Although the mechanisms through which loneliness "gets under the skin" to influence the risk of developing CI have been conceptually proposed, they are rarely empirically examined. The Evolutionary Theory of Loneliness posits that loneliness as a stressor could cause dysregulations in multiple physiological systems. The current study investigated whether inflammatory, cardiovascular, and kidney biomarkers mediate the longitudinal association between loneliness and CI.

METHODS

Cross-lagged panel models were used to examine the hypothesized relationships, using 2006, 2010, and 2014 waves of data from the Health and Retirement Study (N = 7,037). Loneliness was measured with the 3-item UCLA loneliness scale. CI was assessed with the modified telephone interview for cognitive status. Biomarkers included HbA1C, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, C-reactive protein, and Cystatin C. Using a stepwise model-building approach, first, the model included only loneliness, CI, and biomarker variables; then, sociodemographic covariates were added; lastly, health status were controlled for.

RESULTS

In unadjusted and partially adjusted models, loneliness was associated with higher odds of worse cognitive status in an 8-year follow-up. Only HbA1C mediated the longitudinal association between loneliness and CI. However, after further controlling for health status, all associations became nonsignificant.

CONCLUSIONS

Examining a large number of participants and linking a limited number of biological markers with cognition and loneliness longitudinally, our empirical data did not support theoretical propositions, highlighting the critical importance of controlling for confounders in future studies examining longitudinal mediational relationships underlying loneliness and CI.

Loneliness, positive, negative and disorganised Schizotypy before and during the COVID-19 pandemic

Loneliness is common in psychosis and occurs along a continuum. Here we investigate inter-relationships between loneliness, three-dimensional schizotypy, and depressive symptoms before and during the COVID-19 pandemic.

The sample included 507 university students (48.3% participated before and 51.7% during the COVID-19 pandemic) who completed the Multidimensional Schizotypy Scale-Brief, the Counseling Center Assessment of Psychological Symptoms depression scale and the University of California, Los Angeles Loneliness Scale. Schizotypy and depression scores were regressed onto loneliness individually and in multiple regressions.

The cohorts did not differ in any of the schizotypy domains (all p > .29). Depressive symptoms (p = .05) and loneliness (p = .006) were higher during the pandemic than before. Across cohorts, loneliness was significantly associated with positive (β = 0.23, p < .001), negative (β = 0.44, p < .001), and disorganised schizotypy (β = 0.44, p < .001), and with depression (β = 0.72, p < .001). Schizotypy together explained a significant amount of variance in loneliness (R² = 0.26), with significant associations with positive (β = −0.09, p = .047), negative (β = 0.31, p < .001) and disorganised schizotypy (β = 0.34, p < .001). When depression was included (β = 0.69, p < .001), only positive (β = −0.09, p = .008) and negative schizotypy (β = 0.22, p < .001) significantly predicted loneliness.

When all schizotypy dimensions and depression were considered together, only negative schizotypy and depression significantly predicted loneliness. Loneliness and depressive symptoms were higher during the pandemic, but this did not relate to cohort differences in schizotypy.

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Loneliness is uniquely associated with negative schizotypy and depression, but not disorganised schizotypy.

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Certain aspects of positive schizotypy may protect against loneliness.

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Loneliness and depressive symptoms were higher in students during the COVID-19 pandemic than before.

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Cohorts of students assessed before and during the pandemic showed similar levels of schizotypy.

The effect of social relationships on cognitive decline in older adults: an updated systematic review and meta-analysis of longitudinal cohort studies

Background

A previous meta-analysis (Kuiper et al., 2016) has shown that multiple aspects of social relationships are associated with cognitive decline in older adults. Yet, results indicated possible bias in estimations of statistical effects due to the heterogeneity of study design and measurements. We have updated this meta-analysis adding all relevant publications from 2012 to 2020 and performed a cumulative meta-analysis to map the evolution of this growing field of research (+80% of studies from 2012-2020 compared to the period considered in the previous meta-analysis).

Methods

Scopus and Web of Science were searched for longitudinal cohort studies examining structural, functional and combined effects of social relationships. We combined Odds Ratios (OR) with 95% confidence intervals (CI) using random effects meta-analysis and assessed sources of heterogeneity and the likelihood of publication bias. The risk of bias was evaluated with the Quality of Prognosis Studies in Systematic Reviews (QUIPS) tool.

Results

The review was prospectively registered on PROSPERO (ID: CRD42019130667). We identified 34 new articles published in 2012-2020. Poor social relationships were associated with cognitive decline with increasing precision of estimates compared to previously reviewed studies [(for structural, 17 articles, OR: 1.11; 95% CI: 1.08; 1.14) (for functional, 16 articles, OR: 1.12; 95% CI: 1.05; 1.20) (for combined, 5 articles, OR: 1.15; 95% CI: 1.06; 1.24)]. Meta-regression, risk and subgroup analyses showed that the precision of estimations improved in recent studies mostly due to increased sample sizes.

Conclusions

Our cumulative meta-analysis would confirm that multiple aspects of social relationships are associated with cognitive decline. Yet, there is still evidence of publication bias and relevant information on study design is often missing, which could lead to an over-estimation of their statistical effects.

Supplementary Information

The online version contains supplementary material available at (10.1186/s12889-022-12567-5).

Is Loneliness a Cause or Consequence of Dementia? A Public Health Analysis of the Literature

Loneliness has been reframed from a 'social problem of old age' into a major public health problem. This transformation has been generated by findings from observational studies of a relationship between loneliness and a range of negative health outcomes including dementia. From a public health perspective, key to evaluating the relationship between loneliness and dementia is examining how studies define and measure loneliness, the exposure variable, and dementia the outcome. If we are not consistently measuring these then building a body of evidence for the negative health outcomes of loneliness is problematic. Three key criteria had to meet for studies to be included in our analysis. To test the proposition that loneliness is a cause of dementia we only included longitudinal studies. For inclusion studies had to measure loneliness at baseline, have samples free of dementia and assess dementia at follow up (specified as a minimum of 12 months). We identified 11 papers published between 2000 and 2018 that meet these criteria. These studies included seven different countries and only one was specifically focused upon dementia: all other studies were cohort studies focused upon ageing and health and wellbeing. There was extensive heterogeneity in how studies measured loneliness and dementia and in the use of co-variates. Loneliness was measured by either self-rating scales (n = 8) or scales (n = 3). Dementia was assessed by clinical tests (n = 5), diagnostic/screening tools (n = 3), cognitive function tests (n = 1), and self-reported doctor diagnosis (n = 2). Substantial variation in loneliness prevalence (range 5-20%) and dementia incidence (5-30 per 1000 person years at risk). Six studies did not report a statistically significant relationship between loneliness and dementia. Significant excess risk of dementia among those who were lonely ranged from 15% to 64%. None of these studies are directly comparable as four different loneliness and dementia measures were used. We suggest that the evidence to support a relationship between loneliness and dementia is inconclusive largely because of methodological limitations of existing studies. If we wish to develop this evidence base, then using a consistent set of loneliness and dementia outcome measures in major longitudinal studies would be of benefit.