Being more socially active in your 50s and 60s predicts a lower risk of developing dementia later on, finds a new UCL-led study.
The longitudinal study, published in PLOS Medicine, reports the most robust evidence to date that social contact earlier in life could play an important role in staving off dementia.
“Dementia is a major global health challenge, with one million people expected to have dementia in the UK by 2021, but we also know that one in three cases are potentially preventable,” said the study’s lead author, Dr. Andrew Sommerlad (UCL Psychiatry).
“Here we’ve found that social contact, in middle age and late life, appears to lower the risk of dementia.
This finding could feed into strategies to reduce everyone’s risk of developing dementia, adding yet another reason to promote connected communities and find ways to reduce isolation and loneliness.”
The research team used data from the Whitehall II study, tracking 10,228 participants who had been asked on six occasions between 1985 and 2013 about their frequency of social contact with friends and relatives.
The same participants also completed cognitive testing from 1997 onwards, and researchers referred to the study subjects’ electronic health records up until 2017 to see if they were ever diagnosed with dementia.
For the analysis, the research team focused on the relationships between social contact at age 50, 60 and 70, and subsequent incidence of dementia, and whether social contact was linked to cognitive decline, after accounting for other factors such as education, employment, marital status and socioeconomic status.
The researchers found that increased social contact at age 60 is associated with a significantly lower risk of developing dementia later in life.
The analysis showed that someone who saw friends almost daily at age 60 was 12% less likely to develop dementia than someone who only saw one or two friends every few months.
They found similarly strong associations between social contact at ages 50 and 70 and subsequent dementia; while those associations did not reach statistical significance, the researchers say that social contact at any age may well have a similar impact on reducing dementia risk.
Social contact in mid to late life was similarly correlated with general cognitive measures.
Previous studies have found a link between social contact and dementia risk, but they did not have such long follow-up times, so they could not rule out the possibility that the beginnings of cognitive decline may have been causing people to see fewer people, rather than the other way around.
The long follow-up in the present study strengthens the evidence that social engagement could protect people from dementia in the long run.
The researchers say there are a few explanations for how social contact could reduce dementia risk.
“People who are socially engaged are exercising cognitive skills such as memory and language, which may help them to develop cognitive reserve – while it may not stop their brains from changing, cognitive reserve could help people cope better with the effects of age and delay any symptoms of dementia,” said senior author Professor Gill Livingston (UCL Psychiatry).
“Spending more time with friends could also be good for mental wellbeing, and may correlate with being physically active, both of which can also reduce the risk of developing dementia,” added Professor Livingston, who previously led a major international study outlining the lifecourse factors that affect dementia risk.
The researchers were supported by Wellcome and the National Institute for Health Research UCLH Biomedical Research Centre, while the Whitehall II study is supported by the US National Institutes of Health, UK Medical Research Council and the British Heart Foundation.
The study was conducted by researchers in UCL Psychiatry, UCL Epidemiology & Public Health, Camden & Islington NHS Foundation Trust and Inserm.
Dr. Kalpa Kharicha, Head of Innovation, Policy and Research at the Campaign to End Loneliness, said:
“We welcome these findings that show the benefits of frequent social contact in late/middle age on dementia risk.
As we found in our Be More Us Campaign, almost half of UK adults say that their busy lives stop them from connecting with other people.
It’s important we make changes to our daily lives to ensure we take the time to connect with others.
We need more awareness of the benefits that social wellbeing and connectedness can have to tackle social isolation, loneliness and reduce dementia risk.”
Fiona Carragher, Chief Policy and Research Officer at Alzheimer’s Society, said:
“There are many factors to consider before we can confirm for definite whether social isolation is a risk factor or an early sign of the condition – but this study is a step in the right direction.
We are proud of supporting work which helps us understand the condition better – it is only through research that we can understand true causes of dementia and how best to prevent it.
“As the number of people in the UK with dementia is set to rise to one million by 2021, we must do what we can to reduce our risk – so along with reducing your alcohol intake and stopping smoking, we encourage people across the country to get out into the sunshine, and do something active with family and friends.
“The Government’s recent emphasis on health prevention is a welcome opportunity to reduce the risk of dementia across society.
We now need to see Ministers prioritise better support initiatives to help people reduce the risk of dementia, and look forward to seeing this when the results of the Green Paper on Prevention are published later in the year.”
Studies of social network and dementia have looked at a number of social network variables including marital status, living arrangement, number of children, frequency of contacts and satisfaction.
Close social ties has been measured by frequency of contact with friends and relatives and resultant satisfactions.[22] Social engagement has also been measured in capturing external social activities including attending religious services, going to a museum, participation in activities or groups outside home, part time or full time job.[24]
One of the studies was done in a cohort of women in California[23] and another in Japanese-American men in Hawaii.[22]
The rest of the studies reviewed included elderly urban populations of both sexes [Table 1] without previous diagnosis of dementia in Germany, France, Sweden, and the United States of America. The heterogeneity of reviewed studies in cognitive tests and social network measures makes precise comparison of results difficult to some extent.
Table 1
Observational longitudinal studies of the association between social network and dementia[6]
| Study | n | Age at baseline | Social network | Follow-up years | Reported associations |
|---|---|---|---|---|---|
| Bickel and Cooper et al.[15] | 422 | >65 | Social relations, social support, marital status | 5-8 | Being single or widow with increased risk of dementia |
| Fabrigoule et al.[16] | 2040 | >65 | Cultural, productive, and social activities | 3 | Traveling, odd jobs, knitting or gardening with decreased risk of dementia |
| Helmer et al.[17] | 3675 | >65 | Marital status, social network (social ties and satisfaction), number of activities | 5 | Never married with increased risk of dementia and Alzheimer disease, no association with social network and leisure activities |
| Fratiglioni et al.[18] | 1203 | >75 | Marital status, living arrangement, social ties | 3 | Single, living alone or no satisfying feeling with increased dementia, poor and limited social network with increased dementia |
| Scarmeas et al.[19] | 1172 | >65 | 13 selected activities (physical, cultural, recreational and social) | 1-7 Mean 2.9 | Single activity and factor scores (intellectual, physical and social) with decreased risk ofAlzheimer disease, higher leisure activity score with decreased risk |
| Wang et al.[20] | 732 | >75 | Mental, social, recreational, productive and physical activities, frequency of participation | 6 | Frequent engagement in mental, social, and productive activities was inversely related to dementia incidence |
| Karp et al.[21] | 776 | >75 | The leisure activities were grouped into 29 main types of activities. A mental, social, and physical component score was assigned to each of the 29 activities. | 3 | Having high overall scores on all 3 components was associated with significantly lower risks of dementia |
| Single activities scoring high in more than one component had a substantial social component | |||||
| Saczynski et al.[22] | 222 Japanese-American men | Had follow up in both midlife and late life | Marital status, living arrangement, participation in social, political, or community groups number of face-to-face or telephone contacts with close friends per month and the existence of a confidant relationship | Midlife: average of 27.5 years before dementia diagnosis Late life: average of 4.5 years before dementia diagnosis | Lowest late-life social engagement group had a significantly higher risk of dementia Findings were similar when subtypes of dementia (Alzheimer’s disease and vascular dementia) were examined (data not shown) No association between midlife social engagement and risk of dementia |
| Crooks et al.[23] | 2249 women | >78 | Lubben Social Network Scale: active social network, perceived support network and perceived confidant network. Noted frequency of social contact | 5 | Larger social networks and daily social contact have a protective influence on cognitive function among elderly women |
Eight longitudinal cohort studies [Table 1] reported an inverse relation between the level of late-life social contacts or engagement and the risk of dementia/Alzheimer disease.[15–23]
One study[24] looked at possible clinicopathological correlates of social networks measures in subjects developing dementia.
It linked social networks to several measures of Alzheimer disease pathology (a global measure based on modified Bielschowsky silver stain, amyloid load, and the density of neurofibrillary tangles) with several cognitive domains.
Cognitive function was inversely related to all measures of disease pathology, indicating lower function at more severe levels of pathology. Social network size modified the association between pathology and cognitive function in this study, especially for measures of semantic memory and working memory.
The effects were strongest for neurofibrillary tangle pathology.
Even at more severe levels of global disease pathology, cognitive function remained higher for participants with larger network sizes.[24]
The authors speculated that the disease pathology modifying effects of social networks may be explained by trophic effects on brain substrates that are common to socialization and cognition, development of alternate brain networks, or that social networks could be a marker for other healthy behaviors.
One longitudinal study[21] did not find midlife social engagement to be related to dementia risk but late life social engagement had a positive association to dementia.
This was not consistent with the result seen in an earlier case control study[24] which revealed a significant negative association between extensive psychosocial networks even at age thirty with diagnosis of dementia decades later.
Only one study that we reviewed noted a lack of association between social networks and dementia[17] though it did show a positive association to marital status.
Interestingly a study on cognitive decline in a Taiwanese cohort[26] showed no association between social network or support measures at home.
This was despite a social structure where elderly persons often live with their children, and social interaction is likely to be more family-centered than in western countries.
Data from Taiwan seems to suggest that participation in social activities outside the family may have a bigger impact on cognitive function than social contacts with family or non-relatives.
These findings could arise in part as social ties can impose significant emotional demands or involve negative interactions
The results may also be specific to Asian settings, where extra-family social support structures are generally thought to be strong and may not be measured adequately by the frequency of contact with specific individuals, especially family members.[23]
In contrast to the previous study, no associations were seen in Chinese[27] and Canadian[28] cohorts between social activities outside the family and risk of developing cognitive decline. It is therefore still unclear how social activities vs. social support may play a role in preventing cognitive decline in different societies.
Data from longitudinal studies of social networks and dementia so far are has been consistent in showing a protective effect of social networks on dementia.
There are no randomized controlled trails that have looked at the protective effect of social networks on dementia (though this may not be possible to do over a short period) and all studies so far have been from western cohorts.
CAVEATS AND POTENTIAL MECHANISMS FOR THE COGNITIVE BENEFICIAL EFFECTS OF SOCIAL NETWORKS
Cognitive reserve hypothesis
Robert Katzman proposed that individuals with higher educational levels are more resistant to the effects of dementia as a result of improved cognitive reserve due to increased neuronal synaptic complexity. A similar explanation has been proposed to explain the cognitive risk modifying effects of social networks.[24]
A significant burden of dementia in the world is vascular dementia.[29] Vascular risk factors are directly involved in the pathogenesis and progression of these dementias in addition to their involvement in Alzheimer’s dementia.[30]
Cerebrovascular disorders could also promote earlier clinical expression of dementias by reducing cognitive reserve. Social, mental, and physical activities could act via their positive effects on the cardiovascular system and help prevent the progression of dementias.
Social networks as a marker for healthier lifestyle
Neurobiological mechanisms underlying these epidemiological effects are unknown. Subjects with more social engagement could also be self-selecting, with high-ability individuals leading intellectually and socially active lives, which allows the possibilities that residual confounding (the effect of an unmeasured factor) and/or reverse causality (incipient decline affecting the seeking of cognitive stimulation) may explain these associations.[31]
A life course approach to cognitive function would postulate that both biological and psychosocial factors operating in early life may be important.[32]
Social network could be a marker for early life protective factors such as education or it may help maintain the cognitive benefits of education later in life as adjustment for the psychosocial network neutralized the otherwise protective effect of education for dementia of any type and for possible vascular dementia in a case control study.[25] T
hose with larger social networks are also thought be less depressed which also is associated with cognitive decline and dementia. However, the association of social networks with reduced risk of dementia shown in recent studies remains significant even after these confounding effects are taken into consideration.[6,24]
Cultural factors influencing social networks and health
A conceptual model of cascading casual process beginning with the larger social and cultural context that determines the social network structure and characteristics of network ties has been proposed.[5]
Social networks may affect health by operating through five main mechanisms; social support, social influence, social engagement, person-to-person contact and access to material resources and goods which affect health through behavioral, psychological and physiological pathways.
There is now an increasing appreciation of psychological and behavioral intermediate mechanisms through which social networks may affect final biological pathways by disease modification.[33]
Persons living in joint families have larger social networks than in nuclear families. Significant network size differences were shown between joint family males and nuclear family males and females, a patriarchal joint family having a positive impact on aging in terms of gender.
Being an older male in a joint family results in high social involvement.[7] This shows the importance of understanding the social roles and their embededness[34] in the social context as it can lead to differing amount of social involvement.
The type of family structure, the number of social interactions and the social role these interactions play are unanswered in these present studies. Some studies on cognitive aging[33] have shown that the number of social relationships do not affect cognitive decline as much as the quality of relationships.
The quality of relationships and their role in development of dementia has yet to be investigated. These could be captured by variables like changes in the economic and social roles, degree of personal vs. nonpersonal contact (e.g.: use of telephone, internet, etc). These questions also make the cultural context of the recent findings on dementia and social network relevant to keep in mind.
Neurobiological aspects of social cognition
Social cognition is defined as the perception of others, the perception of self and interpersonal knowledge.
The basic cognitive processes in social cognition involve the perception, a social stimulus (the self, other people or the interaction of the two) in varying degrees of complexity. Later stages of elaboration integrate basic perceptions with contextual knowledge and finally involve representations of possible responses to the situation.[35]
A highly social animal engages many perceptual and cognitive systems including vision, audition, speed of processing, episodic memory and attribution of mental states.[36,37]
Deficits in any of these systems that are commonly seen with age could lead to poor social functioning and confound the effects of social networks in the development of dementia. This makes the involvement of a single social module that is more vulnerable in dementia less likely.
In the neuroscience literature two sets of findings, one at a macroscopic level, the other at a microscopic level suggest that the primate brain might contain neural systems specialized for processing socially relevant information.
Selective lesions of the monkey amygdala result in more subtle impairments which appear to impair disproportionately impact those behaviors normally elicited by social cues with abnormal emotional reactivity in social situations being a common occurrence.[38]
At the level of single neurons, neurophysiological studies in non-human primates have shown that single neurons in the monkey inferotemporal cortex respond relatively selectively to the sight of faces, modulate their response preferentially with specific information about faces, such as their identity, social status or emotional expression and are modulated by viewing complex scenes of social interaction and specific features of faces that can signal social information, such as gaze direction.[38,39]
Several developmental disorders including autism spectrum disorders, schizophrenia, behavioral variant frontotemporal dementia (FTD) and Parkinson’s disease have impaired ability to maintain social ties.[39,41] Studies converge on a set of neural structures that are presumed to mediate our perception and interpretation of the social meaning of other people.
These include higher-order visual cortices in the temporal lobe, amygdale and orbitofrontal cortex, and additional cortical regions, such as the left prefrontal and right parietal cortices, these have been implicated in maintaining self vs. non-self thoughts, feelings and other aspects of normal social functioning including episodic and semantic memory.[38]
Damage to these areas by progressive degenerative disorders or neurodevelopmental abnormalities are thought to mediate poor social functioning in these conditions. In contrast to FTD, Alzheimer disease often spares social functioning until late in its course, damaging instead a posterior hippocampal-cingulo temporal-parietal network involved in episodic memory retrieval.[42]
The present epidemiological work on the role of social networks and dementia do not always take the varieties of pathological variations seen in dementia like Alzheimer dementia, vascular dementia, and frontotemporal dementia into consideration.
In animal studies, environmental complexity and richness (argued to be the equivalent of a rich social environment in a human context) prevent cognitive decline,[43] decrease amyloid load,[44] and promote neurogenesis.[45]
Enriched transgenic mice expressing amyloid precursor protein (APP), presenilin1 (PS1) and APP X PS1 perform significantly better in cognitive tests than their standard-housed counterparts after five to seven months of enrichment housing and maintain the same level of performance as wild-type controls kept in standard cages.[46]
In the animal models of neurodegenerative diseases it is still unclear at what time period from dementia the interventions are most effective or if they are protective towards development of dementia.
Social networks as a stress reduction mechanism
Active individuals with more frequent contacts and integration have more opportunities for social engagement and positive emotional states.
This could potentially lead to lower stress, though there is a counter argument to be made for the role of stressful relationships in society.
The stress response and levels of associated hormones, which have been linked to brain function,[2] have been postulated to be modified by social engagement.
Over weeks, months, or years, exposure to increased secretion of stress hormones can result in allostatic load and its pathophysiologic consequences.
Most common allostatic responses involve the sympathetic nervous systems and the hypothalamic-pituitary-adrenal axis.[47]
Aged subjects showing a significant increase in cortisol levels with years and with high current basal cortisol levels were impaired on tasks measuring explicit memory and selective attention when compared to aged subjects presenting either decreasing cortisol levels with years or increasing cortisol levels with moderate current basal cortisol levels.[48]
Assessments of declarative and spatial memory have shown individual differences in brain aging concomitant with atrophy of the hippocampus and progressive elevation of cortisol.[49] Social interactions have been shown as having stress buffering property in the aged and improving functional outcome.[50]
More information:PLOS Medicine (2019). DOI: 10.1371/journal.pmed.1002862
Journal information: PLoS Medicine
Provided by University College London
