The Association Between Loneliness and Inflammation: Findings From an Older Adult Sample

Psychological and neurobiological mechanisms involved in the relationship between loneliness and cognitive decline in older adults

Loneliness, among older adults, is one of the risk factors for developing dementia. Still, little is known about the neurobiological and psychological conditions that link loneliness to cognitive decline. The current study investigated several research aims: First, it sought to identify neurobiological and psychological pathways that may account for the relationship between loneliness and decline across several cognitive domains. These pathways included depressive symptoms, total gray matter volume, and conditional analyses of pro-inflammatory cytokines and brain-derived neurotrophic factor (BDNF) expression. Second, it examined loneliness as a predictor of mild cognitive impairment (MCI) and Alzheimer's disease (AD). Third, it sought to determine whether the relationship between loneliness and cognitive decline is sex-specific in older adults. Longitudinal data were collected from 2130 Rush Memory and Aging Project participants. Participants underwent annual cognitive and psychological assessments and neuroimaging procedures every year. BDNF gene expression was measured in the dorsolateral prefrontal cortex, cytokines were measured in serum, and the final consensus clinical diagnosis was identified at the time of death. All linear mixed and multinomial logistic regression models controlled for age at baseline, education, sex, and APOE genotype. Participants were largely women (73 %), and Caucasian (93 %). The average education was 14.93 (SD = 3.34). The average age at baseline was 80.05 (SD = 7.57). Results showed that gray matter volume and depressive symptoms partially mediated the relationship between loneliness and cognitive decline. There was a significant interaction between loneliness and BDNF expression in relation to cognitive decline. Higher levels of BDNF expression was associated with slower decline in semantic memory and visuospatial ability. Finally, the current study also established that higher levels of loneliness was positively associated with the incidence of AD and other dementias. The present findings support the growing literature, which tends to show that the consequence of loneliness goes beyond the feeling of being isolated. Loneliness may induce physiological changes in our brains, leading to cognitive decline. Future research can explore a wide range of biological and psychological expressions of loneliness to clarify how loneliness relates to dementia.

Remotely-administered resilience and self-compassion intervention targeting loneliness and stress in older adults: a single-case experimental design

OBJECTIVES

Loneliness and chronic stress are prevalent issues for older adults that have been linked to adverse health outcomes. We conducted a remote resilience and self-compassion intervention targeting loneliness and chronic stress.

METHODS

This study utilized a multiple-phase-change single-case experimental design with three consecutive 6-week phases: control, intervention, follow-up. Assessments and biomarker collection (blood pressure, inflammation, sleep actigraphy) were conducted at each phase. Participants completed a 6-week remotely-administered resilience and self-compassion intervention using techniques from cognitive behavioral therapy and resilience training. Repeated measures ANOVAs were conducted over the 12-week period from control (week 0) to intervention completion (week 12) and over the 18-week period from control (week 0) to follow-up (week 18) in supplemental analyses.

RESULTS

Participants reported a reduction in stress (p < 0.001; ηp2 = 0.15), depression (p =  0.02; ηp2 = 0.08), and loneliness (p = 0.003; ηp2 = 0.18), and an increase in self-compassion (p  =  0.01; ηp2 = 0.13) from control to intervention completion (weeks 0-12). Post-hoc tests revealed that stress reduced significantly during the intervention phase (weeks 6-12) and loneliness reduced significantly during the control phase (weeks 0-6). Some improvements in blood pressure, inflammation, and sleep quality were noted in a subsample of participants.

CONCLUSION

Findings indicate that our remote resilience and self-compassion intervention for older adults targeting loneliness and chronic stress was efficacious.

The Association of Loneliness with Diabetes Is Mediated by Physical Activity and BMI but Not Diet Quality

Loneliness is considered a predictor of poor health through numerous pathways. Mediators of this association has not been extensively explored. The study objective was to determine if diet quality and physical activity are parallel mediators with body mass index (BMI) as the third mediator in the association of loneliness with diabetes. The sample, middle-aged and older African American and White adults, 36-77 years, participated in the second follow-up wave of the prospective Healthy Aging in Neighborhoods of Diversity across the Life Span study, 2013-2017. Loneliness was measured by the UCLA 3-item loneliness scale. Participants were categorized as not diabetic, pre-diabetic, or diabetic based on fasting blood glucose, self-reports, or taking medication for diabetes. The Mean Healthy Eating Index-2010 score was calculated from two 24 h dietary recalls collected using the USDA automated multiple pass method. Physical activity was derived from the Baecke questionnaire. The Hayes PROCESS macro, model #80, was used to perform the mediational analysis. Covariates were age, sex at birth, race, income, alcohol intake, and education. Loneliness was inversely and significantly associated with diet quality and physical activity. The only significant indirect path was loneliness > physical activity > BMI > diabetes. Better understanding of modifiable lifestyle behaviors when developing interventions may improve mental health, thereby improving health.

Older adults' self-reported prospective memory lapses in everyday life: Connections to inflammation and gender

OBJECTIVE

Limited research has focused on the association between inflammatory markers and features of subjective cognitive functioning among older adults. The present work examined links between inflammation and a specific subjective cognitive report: prospective memory (PM), or our memory for future intentions, such as attending an appointment or taking medication.

METHOD

We assessed self-reported PM lapses using a two-week ecological momentary assessment (EMA) diary protocol via smartphone as well as levels of blood-based inflammation among 231 dementia-free older adults (70-90 years, 66% women) enrolled in the Einstein Aging Study.

RESULTS

Overall, PM lapses were largely unrelated to inflammatory markers. However, a significant gender difference was observed in the link between basal levels of interleukin (IL)-8 and PM lapses: higher levels of basal IL-8 were associated with more PM lapses among men (estimate = 0.98, 95%CI: [0.43, 1.53], p < .001) but not women (estimate = -0.03, 95%CI: [-0.45, 0.39], p = .826). No other significant relationships between PM lapses and basal or stimulated (ex vivo) cytokine levels (IL-1β, IL-4, IL-6, IL-8, IL-10, tumor necrosis factor-alpha [TNF-α]) or C-reactive protein (CRP) emerged.

CONCLUSION

Elevated levels of IL-8 in older men may possibly be an early indicator of neurodegeneration that relates to PM performance. Future studies should continue to examine PM and inflammation across genders to identify possible mechanisms through which these constructs may indicate neurodegeneration and dementia risk.

Sex-specific impacts of social isolation on loneliness, depressive symptoms, cognitive impairment, and biomarkers: Results from the social environment and biomarker of aging study

OBJECTIVES

To investigate sex-specific associations between social isolation and psychological outcomes and biomarkers among community-dwelling middle-aged and older adults using a nationally representative population-based cohort study.

METHODS

Data from 757 participants from the Social Environment and Biomarkers of Aging Study (SEBAS) were retrieved for analysis, and all participants were stratified by sex. The associations between social isolation and psychological outcomes (loneliness, depressive symptoms, and cognitive impairment) at the 4-year follow-up were examined by multivariate logistic regression models, and associations between social isolation and biomarkers at the 4-year follow-up were examined by multivariate generalized linear models (GLMs).

RESULTS

For men, social isolation was not associated with the development of loneliness. However, being married (adjusted odds ratio (aOR) 0.32 [95% confidence interval (CI) 0.13-0.74], p<0.001) was associated with a lower risk of loneliness, indicating potential protective effects of marriage for men. On the other hand, social isolation was associated with a 2-fold higher risk of loneliness in women (aOR 2.26 [1.01-5.09], p<0.001). Social isolation was not associated with depressive symptoms after adjusting for other demographics. For men, being married (aOR 0.51 [0.26-0.99], p<0.05) or having good self-reported health (aOR 0.44 [0.21-0.92], p<0.05) was protective against depressive symptoms. For women, only good self-reported health (aOR 0.30 [0.13-0.70], p<0.01) provided protective effects against depressive symptoms. Similarly, other demographic factors (being married and having a higher educational level) but not social isolation were associated with lower risks of cognitive impairment. No significant associations were noted between social isolation and selected biomarkers.

CONCLUSIONS

Sex-different associations between social isolation and loneliness were noted; the effects of demographic factors, such as being married, self-reported health status, and high education levels, on subsequent loneliness, depression, and cognitive function were also sex-different. Further intervention studies are needed to explore sex-specific approaches to deal with the interplay of social isolation, loneliness, psychological outcomes and other demographic factors.

Relationships between Interpersonal Goals and Loneliness in Older Adults: A Cross-Sectional Study

Loneliness is linked to many physiological and psychological issues and disproportionately affects older adults. Interpersonal goals (compassion and self-image) are essential to interpersonal relationships; however, how they relate to loneliness in older adults is unknown. We investigated the impact of interpersonal goals on loneliness using the Ecosystem-Egosystem Theory of Social Motivation. This study, adopting a descriptive cross-sectional correlational design, used data from the 2016 Health and Retirement Study. Participants (n = 3212) included people aged >65 years (mean age: 75; female: 60.1%). We performed exploratory factor analysis with principal axis factoring and varimax rotation to examine the suitability of compassionate and self-image goals as separate factors. The complex samples general linear model was used to assess the relationship between loneliness and interpersonal goals. Interpersonal goals were significantly negatively associated with loneliness. Respondents with higher compassion and self-image goals reported lower loneliness levels. Our results contribute to understanding how interpersonal goals relate to loneliness in older adults. These initial findings warrant further investigation.

Palmatine ameliorates LPS-induced HT-22 cells and mouse models of depression by regulating apoptosis and oxidative stress

Depression is one of the most common neuropsychiatric disorders that is characterized by low mood, lack of motivation, slow thinking, and recurrent suicidal thoughts. The mechanism of action of palmatine in depression has been rarely reported and remains unclear. The present study examined the neuroprotective effects of palmatine on lipopolysaccharide (LPS)-induced oxidative stress, apoptosis, and depression-like behavior. In this study, cell apoptosis was evaluated by CCK-8, flow cytometry, and Hoechst 33258 staining in LPS-induced HT-22 cells. Meanwhile, reactive oxygen species (ROS) and mitochondrial membrane potential were detected in vitro. In vivo, we investigated depressive-like behaviors in mice by an open field test (OFT) and elevated plus-maze test (EPM). Additionally, the levels of superoxide dismutases (SOD), TNF-α, IL-1β, and IL-6 were detected by enzyme-linked immunosorbent assay. The hematoxylin-eosin staining and TUNEL staining were used to evaluate the pathology of the hippocampus. The expression of Nrf2/HO-1 and BAX/Bcl-2 pathways in the hippocampus were assessed by Western blot analysis. Palmatine could significantly reduce apoptosis and ROS levels, and improve mitochondrial damage. Moreover, palmatine significantly improves movement time and central square crossing time in OFT, and improves open arms and movement time in EMP. And the levels of SOD, TNF-α, IL-1β, and IL-6 were significantly decreased after palmatine treatment. More importantly, palmatine improved neuronal apoptosis in the hippocampus, and depression through BAX/Bcl-2 and Nrf2/HO-1 signaling pathways. We provide evidence that palmatine further alleviates the depressive-like behavior of LPS-induced by improving apoptosis and oxidative stress.

Affective Neuroscience of Loneliness: Potential Mechanisms underlying the Association between Perceived Social Isolation, Health, and Well-Being

Loneliness, or the subjective feeling of social isolation, is an important social determinant of health. Loneliness is associated with poor physical health, including higher rates of cardiovascular disease and dementia, faster cognitive decline, and increased risk of mortality, as well as disruptions in mental health, including higher levels of depression, anxiety, and negative affect. Theoretical accounts suggest loneliness is a complex cognitive and emotional state characterized by increased levels of inflammation and affective disruptions. This review examines affective neuroscience research on social isolation in animals and loneliness in humans to better understand the relationship between perceptions of social isolation and the brain. Loneliness associated increases in inflammation and neural changes consistent with increased sensitivity to social threat and disrupted emotion regulation suggest interventions targeting maladaptive social cognitions may be especially effective. Work in animal models suggests the neural changes associated with social isolation may be reversible. Therefore, ameliorating loneliness may be an actionable social determinant of health target. However, more research is needed to understand how loneliness impacts healthy aging, explore the role of inflammation as a potential mechanism in humans, and determine the best time to deliver interventions to improve physical health, mental health, and well-being across a diverse array of populations.