The concept of cognitive reserve (CR) explains individual differences in susceptibility to age-related brain changes and Alzheimer's disease (AD) pathology. CR can be categorized into brain reserve, which refers to actual differences in brain structure that may increase tolerance to pathology, and cognitive reserve, which refers to individual differences in how tasks are performed. Epidemiological studies suggest that educational and occupational attainment, as well as leisure activities, can increase CR. Higher levels of education and occupational attainment are associated with a reduced risk of developing AD, while engaging in more leisure activities is linked to a lower risk of dementia. Neuroimaging studies using resting regional cerebral blood flow (rCBF) have shown that individuals with higher CR tolerate more AD pathology, as evidenced by more advanced AD-related changes in brain regions such as the parietotemporal area. Functional imaging studies have also explored the neural mechanisms underlying CR, suggesting that it may involve neural reserve and neural compensation. Neural reserve refers to the resilience of pre-existing cognitive networks, while neural compensation involves the recruitment of alternative cognitive resources. The clinical implications of CR include the need to consider it in diagnostic formulations and clinical trials, as higher CR is associated with more rapid cognitive decline in AD patients. Additionally, CR can influence the effectiveness of treatments, as the rate of decline may be different in patients with higher and lower CR. Finally, the concept of CR supports the idea that interventions in later life can impart reserve, slow cognitive decline, and promote healthy aging. However, controlled studies are needed to translate these findings into practical interventions.The concept of cognitive reserve (CR) explains individual differences in susceptibility to age-related brain changes and Alzheimer's disease (AD) pathology. CR can be categorized into brain reserve, which refers to actual differences in brain structure that may increase tolerance to pathology, and cognitive reserve, which refers to individual differences in how tasks are performed. Epidemiological studies suggest that educational and occupational attainment, as well as leisure activities, can increase CR. Higher levels of education and occupational attainment are associated with a reduced risk of developing AD, while engaging in more leisure activities is linked to a lower risk of dementia. Neuroimaging studies using resting regional cerebral blood flow (rCBF) have shown that individuals with higher CR tolerate more AD pathology, as evidenced by more advanced AD-related changes in brain regions such as the parietotemporal area. Functional imaging studies have also explored the neural mechanisms underlying CR, suggesting that it may involve neural reserve and neural compensation. Neural reserve refers to the resilience of pre-existing cognitive networks, while neural compensation involves the recruitment of alternative cognitive resources. The clinical implications of CR include the need to consider it in diagnostic formulations and clinical trials, as higher CR is associated with more rapid cognitive decline in AD patients. Additionally, CR can influence the effectiveness of treatments, as the rate of decline may be different in patients with higher and lower CR. Finally, the concept of CR supports the idea that interventions in later life can impart reserve, slow cognitive decline, and promote healthy aging. However, controlled studies are needed to translate these findings into practical interventions.