As the incidence of dementia is rapidly increasing around the world, especially in developing countries, it has become one of the most important health and social challenges facing humanity. This volume has reviewed research on social and psychological factors that could moderate the development of dementia in late life through social connection. This last chapter reviews psychosocial interventions connected with various aspects of social connection or lack thereof, such as social networks, social relationships, social engagement, loneliness, and sense of belonging, to examine interventions and their key factors that have shown efficacy in enhancing the moderators. It also introduces three evidence-based components that can be adopted in strategies and policies that aim to reduce the modifiable risks of dementia.

The global population is growing older, and aging and its associated health conditions are challenging individuals, families, and societies. Social isolation has been recognized as a health risk, especially for older adults. More recently, its adverse effects on cognitive and brain health have been reported. On the other hand, various social activities and social networks have been found to have beneficial effects on behavioral as well as brain functions in older adults. It has been difficult, however, to comprehend the full extent and impact of such activities and networks on health, partly due to the complexity of social interactions and human relationships as well as the multilayered aging processes.

South Korea is experiencing the fastest aging of its population in world history, and its dementia population has grown swiftly in the past three decades. This chapter proposes the country’s significance as a case of interest for understanding global population aging and the associated increasing dementia population. A brief history of South Korea, transforming from an agricultural society to a major industrialized nation in less than half a century, demonstrates how major societal changes accompanying industrial development and modernization in a relatively short period have shaped the population aging of a country and its older adults’ risks for dementia. Studies of cognitive aging among elderly Koreans have found greater effects of education on cognitive performance compared to their counterparts in developed countries. As the role of formal education in cognitive development and its moderating effects on neurodegeneration have been found consistently, lack of education has significant consequences on the prevalence of dementia in elderly Koreans, especially women. This has important implications for global aging and dementia epidemiology, as the current increase in the global dementia population is most concentrated in developing countries.

While social disconnection has been consistently perceived as a threat to human beings, objective and subjective social disconnectedness have been associated with poor physical well-being and a higher mortality rate. These factors are equivalent to or more significant than other well-known risk factors, such as smoking. Although mild to severe loneliness persists across the lifespan, correlates of loneliness show age differences, and loneliness affects late-life depression and accelerates the rate of physiological decline with age. In many societies, older adults undergo a transition in social life after retirement or bereavement, leading in many cases to social isolation, which may result in loneliness. This chapter reviews the effects of social isolation on late-life psychological health, focusing on the role of perceived isolation, also known as loneliness. It also discusses multiple risk factors contributing to loneliness, which can be described in terms of trait and state loneliness. Lastly, it notes that not all social connections are beneficial for all when discussing gender differences in social networks.

Sources of resilience against neurodegenerative diseases, such as cognitive reserve, have been identified as modifiable factors that can prevent the manifestation of clinical dementia. A recent trend in dementia research has employed the concepts of reserve and resilience in the context of a lifespan to develop a life course approach, which integrates the risks of dementia and provides prevention strategies throughout life. This chapter introduces the life course approach to understanding dementia, which is a scientific discipline based on the span of life involving biology, psychology, and the social sciences in a single integrated causal structure to provide a framework to organize the multifactorial process involved in human aging and dementia. The cognitive reserve hypothesis and essential studies validating the theory are introduced; these report the moderating effects of literacy and formal education in dementia manifestation. Brain maintenance, another important component in understanding the resistance to brain aging and neurodegenerative diseases, is also discussed. Lastly, the chapter proposes a hypothetical pathway model to help understand the complex interaction between social relation and brain aging underlying the moderation that could either reduce or increase the risks of dementia.

A growing body of evidence suggests a strong link between how individuals maintain an enriched social network and their brain health. Both the quantity and quality of social networks provide abundant social connections. Through persistent social interactions, individuals’ neurocognitive health appears to benefit from cognitively stimulating activity as well as social support. By utilizing various neuroimaging methods, researchers have found that maintaining an enriched social network is likely to lead to better neural functioning that could delay or counter the effects of neuropathological progression in late life. This chapter reviews studies examining the relationship between social network characteristics and neurocognitive health. The studies highlight that social connectedness and brain functioning have reciprocal effects. It also discusses whether larger and cohesively connected social networks lead to a healthier brain and better cognitive function, as well as the moderators of this association.