BackgroundSocial relationships, which are contingent on access to social networks, promote engagement in social activities and provide access to social support. These social factors have been shown to positively impact health outcomes. In the current systematic review, we offer a comprehensive overview of the impact of social activities, social networks and social support on the cognitive functioning of healthy older adults (50+) and examine the differential effects of aspects of social relationships on various cognitive domains.MethodsWe followed PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) guidelines, and collated data from randomised controlled trials (RCTs), genetic and observational studies. Independent variables of interest included subjective measures of social activities, social networks, and social support, and composite measures of social relationships (CMSR). The primary outcome of interest was cognitive function divided into domains of episodic memory, semantic memory, overall memory ability, working memory, verbal fluency, reasoning, attention, processing speed, visuospatial abilities, overall executive functioning and global cognition.ResultsThirty-nine studies were included in the review; three RCTs, 34 observational studies, and two genetic studies. Evidence suggests a relationship between (1) social activity and global cognition and overall executive functioning, working memory, visuospatial abilities and processing speed but not episodic memory, verbal fluency, reasoning or attention; (2) social networks and global cognition but not episodic memory, attention or processing speed; (3) social support and global cognition and episodic memory but not attention or processing speed; and (4) CMSR and episodic memory and verbal fluency but not global cognition.ConclusionsThe results support prior conclusions that there is an association between social relationships and cognitive function but the exact nature of this association remains unclear. Implications of the findings are discussed and suggestions for future research provided.Systematic review registrationPROSPERO 2012: CRD42012003248.Electronic supplementary materialThe online version of this article (10.1186/s13643-017-0632-2) contains supplementary material, which is available to authorized users.

Purpose: Loneliness is a recognised public-health concern that is traditionally regarded as a unidimensional construct. Theories of loneliness predict the existence of subtypes of loneliness. In this study, latent class analysis (LCA) was used to test for the presence of loneliness subtypes and to examine their association with multiple mental health variables. Methods: A nationally representative sample of US adults (N = 1,839) completed the De Jong Gierveld Loneliness Scale, along with self-report measures of childhood and adulthood trauma, psychological wellbeing, major depression, and generalized anxiety. Results: When treated as a unidimensional construct, 17.1% of US adults aged 18-70 were classified as lonely. However, the LCA results identified four loneliness classes which varied quantitatively and qualitatively: 'low' (52.8%), 'social' (8.2%), 'emotional' (26.6%), and 'social and emotional' (12.4%) loneliness. The 'social and emotional' class were characterised by the highest levels of psychological distress, followed by the 'emotional' class. The 'social' loneliness class had similar mental health scores as the 'low' loneliness class. Childhood and adulthood trauma were independently related to the most distressed loneliness classes. Conclusions: Current findings provide support for the presence of subtypes of loneliness and show that they have unique associations with mental health status. Recognition of these subtypes of loneliness revealed that the number of US adults aged 18-70 experiencing loneliness was twice as high as what was estimated when loneliness was conceptualized as a unidimensional construct. The perceived quality, not the quantity, of interpersonal connections was associated with poor mental health.

The COVID-19 global pandemic and subsequent public health social measures have challenged our social and economic life, with increasing concerns around potentially rising levels of social isolation and loneliness. This paper is based on cross-sectional online survey data (available in 10 languages, from 2 June to 16 November 2020) with 20,398 respondents from 101 different countries. It aims to help increase our understanding of the global risk factors that are associated with social isolation and loneliness, irrespective of culture or country, to support evidence-based policy, services and public health interventions. We found the prevalence of severe loneliness was 21% during COVID-19 with 6% retrospectively reporting severe loneliness prior to the pandemic. A fifth were defined as isolated based on their usual connections, with 13% reporting a substantial increase in isolation during COVID-19. Personal finances and mental health were overarching and consistently cross-cutting predictors of loneliness and social isolation, both before and during the pandemic. With the likelihood of future waves of COVID-19 and related restrictions, it must be a public health priority to address the root causes of loneliness and social isolation and, in particular, address the needs of specific groups such as carers or those living alone.

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