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.