In this presentation, we will summarise the observational and interventional evidence linking social participation with dementia risk, the potential mechanisms, and consider what this evidence means for future clinical and policy interventions.

Social participation encompasses several concepts including social activity, contact and support. International observational study evidence finds people who participate less socially in mid or late-life have increased risk of developing dementia. More social contact and less loneliness are consistently associated with less dementia risk in studies with long and short follow-up. However, this is not true of perceived social support.

People who participate socially in late life may be able to do so because they are cognitively intact, so some studies limit their analyses to those without dementia over 10 years before follow-up or consider social participation trajectories. Within social activities, studies use heterogenous definitions, some including individual activities such as crosswords as social activity, and others requiring group activities and some cognitively stimulating activities. Those with shorter follow-up periods find social activity is more protective, suggesting part of the effect is reverse causality.

The postulated mechanisms for social participation’s effects include increasing cognitive reserve, which provides resilience to neuropathological damage, and improved brain maintenance related to a healthier lifestyle, lower stress response, reduced cellular ageing and inflammatory response. The relationship between social participation, depression and hearing is complex with each reinforcing the other and each being associated with dementia.

It is difficult to trial the effect of increasing social participation which might need unacceptable, impractical and long-term interventions (in line with findings that married compared to single people have lower dementia risk). Facilitator-led social group interventions have been small and short with inconsistent effects on cognition.

Overall, the increasing, consistent and biologically plausible evidence that social participation reduces dementia risk means that interventions should begin to be included within dementia prevention guidelines and considered in policy. Public health policy should be an important component through promoting participation in those at risk and improving the accessibility of buildings and cities. This should be targeted at those who are more isolated, and this is closely linked with socio-economic deprivation.