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Oken BS, Kaplan J, Klee D, Gallegos AM. Contributions of loneliness to cognitive impairment and dementia in older adults are independent of other risk factors and Alzheimer's pathology: a narrative review. Front Hum Neurosci 2024; 18:1380002. [PMID: 38873650 PMCID: PMC11169707 DOI: 10.3389/fnhum.2024.1380002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Accepted: 05/20/2024] [Indexed: 06/15/2024] Open
Abstract
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.
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Affiliation(s)
- Barry S. Oken
- Department of Neurology, Oregon Health and Science University, Portland, OR, United States
- Department of Behavioral Neuroscience, Oregon Health and Science University, Portland, OR, United States
| | - Josh Kaplan
- Department of Neurology, Oregon Health and Science University, Portland, OR, United States
| | - Daniel Klee
- Department of Neurology, Oregon Health and Science University, Portland, OR, United States
| | - Autumn M. Gallegos
- Department of Psychiatry, University of Rochester Medical Center, Rochester, NY, United States
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Stafford J, Dekhtyar S, Welmer AK, Vetrano DL, Grande G, Laukka EJ, Marseglia A, Moulton V, Mansfield R, Liu Y, Ning K, Wolf-Ostermann K, Brodaty H, Samtani S, Ikram MA, Melis R, Rymaszewska J, Szcześniak D, Di Gessa G, Richards M, Davis D, Patalay P, Maddock J. 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. THE LANCET. HEALTHY LONGEVITY 2024; 5:e356-e369. [PMID: 38705153 DOI: 10.1016/s2666-7568(24)00046-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Revised: 03/11/2024] [Accepted: 03/11/2024] [Indexed: 05/07/2024] Open
Abstract
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.
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Affiliation(s)
- Jean Stafford
- MRC Unit for Lifelong Health and Ageing at UCL, Faculty of Population Health Sciences, University College London, London, UK.
| | - Serhiy Dekhtyar
- Aging Research Center, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet and Stockholm University, Stockholm, Sweden
| | - Anna-Karin Welmer
- Aging Research Center, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet and Stockholm University, Stockholm, Sweden; Division of Physiotherapy, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, Stockholm, Sweden; Women's Health and Allied Health Professionals Theme, Medical Unit, Medical Psychology, Karolinska University Hospital, Stockholm, Sweden; Stockholm Gerontology Research Centre, Stockholm, Sweden
| | - Davide L Vetrano
- Aging Research Center, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet and Stockholm University, Stockholm, Sweden
| | - Giulia Grande
- Aging Research Center, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet and Stockholm University, Stockholm, Sweden
| | - Erika J Laukka
- Aging Research Center, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet and Stockholm University, Stockholm, Sweden; Stockholm Gerontology Research Centre, Stockholm, Sweden
| | - Anna Marseglia
- Division of Clinical Geriatrics, Center for Alzheimer Research, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, Stockholm, Sweden
| | - Vanessa Moulton
- Centre for Longitudinal Studies, UCL Institute of Education, University College London, London, UK
| | - Rosie Mansfield
- Centre for Longitudinal Studies, UCL Institute of Education, University College London, London, UK
| | - Yiwen Liu
- MRC Unit for Lifelong Health and Ageing at UCL, Faculty of Population Health Sciences, University College London, London, UK
| | - Ke Ning
- Division of Community Medicine and Public Health Practice, School of Public Health, University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China
| | - Karin Wolf-Ostermann
- Institute for Public Health and Nursing Research, University of Bremen, Bremen, Germany; Leibniz Science Campus Digital Public Health, Bremen, Germany
| | - Henry Brodaty
- Centre for Healthy Brain Ageing, Discipline of Psychiatry and Mental Health, Faculty of Medicine and Health, UNSW Sydney, Sydney, NSW, Australia
| | - Suraj Samtani
- Centre for Healthy Brain Ageing, Discipline of Psychiatry and Mental Health, Faculty of Medicine and Health, UNSW Sydney, Sydney, NSW, Australia
| | | | - René Melis
- Department of Geriatric Medicine, Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, Netherlands
| | - Joanna Rymaszewska
- Department of Clinical Neuroscience, Faculty of Medicine, Wrocław University of Science and Technology, Wrocław, Poland
| | - Dorota Szcześniak
- Division of Psychotherapy and Somatic Medicine, Department of Psychiatry, Wrocław Medical University, Wrocław, Poland
| | - Giorgio Di Gessa
- UCL Research Department of Epidemiology & Public Health, Institute of Epidemiology & Health Care, University College London, London, UK
| | - Marcus Richards
- MRC Unit for Lifelong Health and Ageing at UCL, Faculty of Population Health Sciences, University College London, London, UK
| | - Daniel Davis
- MRC Unit for Lifelong Health and Ageing at UCL, Faculty of Population Health Sciences, University College London, London, UK
| | - Praveetha Patalay
- MRC Unit for Lifelong Health and Ageing at UCL, Faculty of Population Health Sciences, University College London, London, UK; Centre for Longitudinal Studies, UCL Institute of Education, University College London, London, UK
| | - Jane Maddock
- MRC Unit for Lifelong Health and Ageing at UCL, Faculty of Population Health Sciences, University College London, London, UK
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Lynch M, Em Arpawong T, Beam CR. Associations Between Longitudinal Loneliness, DNA Methylation Age Acceleration, and Cognitive Functioning. J Gerontol B Psychol Sci Soc Sci 2023; 78:2045-2059. [PMID: 37718577 PMCID: PMC10699733 DOI: 10.1093/geronb/gbad128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Indexed: 09/19/2023] Open
Abstract
OBJECTIVES Loneliness may influence aging biomarkers related to cognitive functioning, for example, through accelerated DNA methylation (DNAm) aging. METHODS In the present study, we tested whether six common DNAm age acceleration measures mediated the effects of baseline loneliness and five different longitudinal loneliness trajectories on general cognitive ability, immediate memory recall, delayed memory recall, and processing speed in 1,814 older adults in the Health and Retirement Study. RESULTS We found that baseline loneliness and individuals who belong to the highest loneliness trajectories had poorer general cognitive ability and memory scores. Only DNAm age acceleration measures that index physiological comorbidities, unhealthy lifestyle factors (e.g., smoking), and mortality risk-mediated effects of baseline loneliness on general cognitive ability and memory functioning but not processing speed. These same DNAm measures mediated effects of the moderate-but-declining loneliness trajectory on cognitive functioning. Additionally, immediate and delayed memory scores were mediated by GrimAge Accel in the lowest and two highest loneliness trajectory groups. Total and mediated effects of loneliness on cognitive functioning outcomes were mainly accounted for by demographic, social, psychological, and physiological covariates, most notably self-rated health, depressive symptomatology, objective social isolation, and body mass index. DISCUSSION Current findings suggest that DNAm biomarkers of aging, particularly GrimAge Accel, have promise for explaining the prospective association between loneliness and cognitive functioning outcomes.
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Affiliation(s)
- Morgan Lynch
- Department of Psychology, University of Southern California, Los Angeles, California, USA
| | - Thalida Em Arpawong
- Davis School of Gerontology, University of Southern California, Los Angeles, California, USA
| | - Christopher R Beam
- Department of Psychology, University of Southern California, Los Angeles, California, USA
- Davis School of Gerontology, University of Southern California, Los Angeles, California, USA
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Affective Neuroscience of Loneliness: Potential Mechanisms underlying the Association between Perceived Social Isolation, Health, and Well-Being. JOURNAL OF PSYCHIATRY AND BRAIN SCIENCE 2022; 7:e220011. [PMID: 36778655 PMCID: PMC9910279 DOI: 10.20900/jpbs.20220011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
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.
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