Diverse and sustained social activities may boost cognitive performance and slow the decline in brain health associated with ageing, suggest the findings of a large international study, published online in the Journal of Epidemiology & Community Health.
Regularly engaging in 3 or more of these activities, and including volunteering and sports club membership among them, seem to be particularly effective at helping to keep minds sharp, the findings indicate.
The global prevalence of dementia, which is preceded by cognitive impairment, is estimated to affect nearly 153 million people by 2050, point out the researchers. While several studies have looked at the association between social activities and both cognitive function and dementia, the findings have been inconsistent, they add.
This might be down to small sample sizes, limited geographic diversity, and differences in the definitions and measurements used for social activity and cognitive outcomes, they suggest.
In a bid to overcome some of these issues, the researchers drew on pooled long term data from 5 nationally representative surveys spanning 24 countries.
These surveys were: the US Health and Retirement Study (HRS, waves 10-15, 2010-21); the English Longitudinal Study of Ageing (ELSA, waves 4-9, 2008-19); the China Health and Retirement Longitudinal Study (CHARLS, waves 1-4, 2011-18); the Mexican Health and Ageing Study (MHAS, waves 3-5, 2012-18); and the Survey of Health, Ageing, and Retirement in Europe (SHARE, waves 4-8, 2011-20).
Participants in each wave were asked about the type and number of social activities they engaged in, and their cognitive performance was assessed at each wave using tests of memory and executive function.
The test results produced a z score of global cognitive function, with higher z scores indicative of better cognitive performance.
In all, 57,793 participants were included in the study. Their average age ranged from 57 to 73, and they were tracked for an average of 6 years.
Analysis of the pooled cognitive z-scores showed that those who engaged in social activities had significantly higher scores than those who didn't, with scores rising in tandem with the number of social activities.
Engaging in at least 3 of these seemed to afford the greatest level of protection against impairments in memory and executive function: those who did this had higher yearly cognitive z-scores during the tracking period than those who engaged in none.
Volunteering and sports club membership were associated with a lower risk of cognitive decline across all 5 groups, while attending training courses and taking care of children were significantly associated with higher cognitive z-scores year on year.
But active involvement in political, community, church, and religious groups wasn't consistently associated with cognitive enhancement.
Further analysis indicated that the positive associations between social activities and cognitive function were stronger among women, those aged 60+, those with higher levels of education, those who weren't depressed, those who lived alone, those of normal weight, those living in rural areas, and those who smoked and/or drank alcohol.
This is an observational study, so can't establish cause and effect. And the researchers acknowledge various limitations to their findings. These include the lack of standardisation across the 5 surveys, only partial adjustment for potentially influential factors, and the focus on the quantity of social activities, to the exclusion of quality, motivation, and experience, all of which may be equally important, they suggest.
It's not entirely clear how social activities might protect against cognitive decline, but there are several plausible explanations, say the researchers.
These include the 'use it or lose it' hypothesis, which proposes that sustained engagement in cognitively stimulating activities may enhance neural plasticity and strengthen synaptic connections.
A higher level of education is also thought to enhance neural efficiency and compensatory capacity, increasing resilience to the neuropathological changes associated with ageing, while participation in meaningful social activities may promote psychological wellbeing. This in turn may modulate neuroendocrine function and lessen the detrimental effects of chronic stress on hippocampal structure and function, say the researchers.
"Collectively, these findings suggest that social activities may operate as a multidimensional protective factor against cognitive deterioration in older adults," they write.
"These results underscore the importance of developing and implementing targeted interventions aimed at promoting diverse and sustained social engagement among older adults as a viable strategy to mitigate the risk of age-related cognitive decline," they conclude.
