Social connectedness and cognitive decline

Abstract

Cognitive impairment is a growing public health concern that affects millions of people worldwide. Alzheimer's disease and related dementia, which represent a leading cause of cognitive decline among older adults, has a high financial burden. Approximately US$1·3 trillion is spent on Alzheimer's disease and related dementia every year worldwide.1WHOGlobal status report on the public health response to dementia.https://www.who.int/publications/i/item/9789240033245Date: Sept 1, 2021Date accessed: September 5, 2022Google Scholar Although there are more than 100 clinical trials of pharmaceutical agents for Alzheimer's disease and related dementia, no effective treatment exists.2Cummings J Lee G Zhong K Fonseca J Taghva K Alzheimer's disease drug development pipeline: 2021.Alzheimers Dement (N Y). 2021; 7e12179Google Scholar In response to the absence of effective pharmaceutical treatment, researchers are investigating non-pharmaceutical pathways leading to cognitive decline in later life. Social connectedness, a broad concept that encapsulates the structure, function, and quality of personal relationships, is a potential universal remedy for cognitive impairment.3Piolatto M Bianchi F Rota M et al.The effect of social relationships on cognitive decline in older adults: an updated systematic review and meta-analysis of longitudinal cohort studies.BMC Public Health. 2022; 22: 278Crossref PubMed Scopus (5) Google Scholar, 4Kelly ME Duff H Kelly S et al.The impact of social activities, social networks, social support and social relationships on the cognitive functioning of healthy older adults: a systematic review.Syst Rev. 2017; 6: 259Crossref PubMed Scopus (288) Google Scholar According to scholars across the medical, social, and psychological sciences, social connectedness most likely works through multiple mechanisms to influence the decline of cognitive function in later life. It has been argued that people who consistently engage in a diversity of social realms exercise their neuropathways in a way that protects them against the degenerative effects of dementia and other age-related cognitive impairments.5Ellwardt L Van Tilburg TG Aartsen MJ The mix matters: complex personal networks relate to higher cognitive functioning in old age.Soc Sci Med. 2015; 125: 107-115Crossref PubMed Scopus (63) Google Scholar, 6Perry BL Roth AR Peng S Risacher SL Saykin AJ Apostolova LG Social networks and cognitive reserve: network structure moderates the association between amygdalar volume and cognitive outcomes.J Gerontol Psychol Sci Soc Sci. 2022; 77: 1490-1500Crossref PubMed Scopus (3) Google Scholar At the same time, evidence also suggests that supportive social relationships buffer against otherwise cognitively damaging life stressors.4Kelly ME Duff H Kelly S et al.The impact of social activities, social networks, social support and social relationships on the cognitive functioning of healthy older adults: a systematic review.Syst Rev. 2017; 6: 259Crossref PubMed Scopus (288) Google Scholar Suraj Samtani and colleagues leverage a large-scale database to build on a wide body of research looking at the association between social connection and cognitive decline.7Samtani S Mahalingam G Lam BCP et al.Associations between social connectedness and cognition: a global collaborative population-based cohort study.Lancet Healthy Longev. 2022; (published online Oct 20.)https://S2666-7568(22)00199-4Summary Full Text Full Text PDF PubMed Google Scholar Using harmonised longitudinal data from 13 studies, the authors conducted a meta-analysis and reported that some—but not all—measures of social connection are linked to future rates of cognitive decline. For instance, they reported that participants who lived with others had slower cognitive decline (ie, in global cognition, memory, and language) than did participants who lived alone. These findings were robust across model specifications. Monthly engagement in community groups and yearly interactions with family and friends, however, were significantly associated with slower global cognitive decline than were never engaging and never interacting, but only in partially adjusted models. Although they hypothesised that the association between social connection markers and cognitive decline would differ by sex, they found minimal support for this claim. In their study, women who were in a relationship or married appeared to have a slower decline in memory than did women who were single or never married, whereas men who were in a relationship or married had faster rates of decline in global cognition during the study period than did men who were single or never married. Aside from relationship status, there were no detectable differences between men and women in this study. The main contribution of their meta-analysis is the inclusion of data on a global range of participants. Whereas previous research on social connectedness and cognition focused largely on participants in either Europe or North America, Samtani and colleagues should be applauded for their collaborative efforts to harmonise a large database from a range of heterogeneous nations. Moreover, they focused specifically on longitudinal studies rather than cross-sectional studies. Understanding the dynamic relationship between social connectedness and cognition adds a nice (although not unprecedented3Piolatto M Bianchi F Rota M et al.The effect of social relationships on cognitive decline in older adults: an updated systematic review and meta-analysis of longitudinal cohort studies.BMC Public Health. 2022; 22: 278Crossref PubMed Scopus (5) Google Scholar) element to their study. As with any empirical analysis, their study is not without limitations. Although Samtani and colleagues impressively analysed data for a range of social connectedness indicators (eg, living arrangement, frequency of social interactions, and community group participation), there are many more nuanced measures that are consistently linked with cognitive impairment and decline. Future research would benefit from including social network data, which casts people in interconnected webs of relationships;6Perry BL Roth AR Peng S Risacher SL Saykin AJ Apostolova LG Social networks and cognitive reserve: network structure moderates the association between amygdalar volume and cognitive outcomes.J Gerontol Psychol Sci Soc Sci. 2022; 77: 1490-1500Crossref PubMed Scopus (3) Google Scholar ecological momentary assessments, which capture real-time data for participants' social lives;8Zhaoyang R Sliwinski MJ Martire LM Katz MJ Scott SB Features of daily social interactions that discriminate between older adults with and without mild cognitive impairment.J Gerontol B Psychol Sci Soc Sci. 2021; (published online Feb 2.)https://doi.org/10.1093/geronb/gbab019Crossref Google Scholar and neighbourhood metrics, such as presence of community centres and other social infrastructures.9Clarke PJ Weuve J Barnes L Evans DA Mendes de Leon CF Cognitive decline and the neighborhood environment.Ann Epidemiol. 2015; 25: 849-854Crossref PubMed Scopus (91) Google Scholar Moreover, Samtani and colleagues were limited to studying the association between baseline measures of social connectedness and cognitive decline, yet social connectedness is known to fluctuate over the life course.10Alwin DF Felmlee DH Kreager DA Social networks and the life course: integrating the development of human lives and social relational networks. Springer International Publishing, Cham2018Crossref Google Scholar, 11Cornwell B Goldman A Laumann EO Homeostasis revisited: patterns of stability and rebalancing in older adults' social lives.J Gerontol B Psychol Sci Soc Sci. 2021; 76: 778-789Crossref PubMed Scopus (13) Google Scholar Although the long-term tracking of participants and changes in their social lives requires considerable time and resources, doing so would help to bolster our understanding of the social mechanisms leading to the development (and ideally prevention) of cognitive decline in later life. I declare no competing interests. Associations between social connections and cognition: a global collaborative individual participant data meta-analysisGood 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. Full-Text PDF Open Access

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