Cognitive decline is a gradual, heterogeneous process characterized by the reduction in cognitive abilities such as processing speed, memory, and executive function. While some degree of decline is a normal part of aging, the trajectory is not uniform across all cognitive domains. A critical distinction exists between fluid intelligence (), which typically declines starting in early adulthood, and crystallized intelligence (), which remains stable or improves until late midlife.
The 2024 Lancet Commission on dementia prevention identifies nearly half of dementia cases as potentially preventable through modifiable risk factors, underscoring that cognitive trajectory is not solely determined by genetics[1].
Cognitive health is a composite of distinct faculties that age at different rates.
The factor represents the underlying correlation between distinct cognitive tasks. Individuals who perform well in one domain (e.g., verbal ability) tend to perform well in others (e.g., spatial reasoning).
Fluid intelligence involves the ability to solve novel problems, use logic in new situations, and identify patterns independent of acquired knowledge.
Crystallized intelligence represents the ability to use learned knowledge and experience.
The speed at which mental operations are performed is often considered a fundamental bottleneck (Salthouse’s Processing Speed Theory)[3].