Why is delirium more frequent in the elderly?

Area of Science:

• Neuroscience
• Gerontology
• Pathophysiology

Background:

• Delirium is more common in the elderly due to age-related declines in brain function.
• Reduced functional reserve in aging brains struggles to meet heightened metabolic demands during stress.

Purpose of the Study:

• To review age-related changes affecting brain functional reserve and complex mental activities.
• To explore how diminished connectivity and other factors contribute to delirium in the elderly.

Main Methods:

• Literature review of aging-related changes impacting cognitive function and brain reserve.
• Analysis of factors contributing to delirium, including synaptic loss and neuroinflammation.

Main Results:

• Aging compromises functional reserve through reduced neuronal/synaptic density and impaired connectivity, particularly affecting association systems and cholinergic fibers.
• Factors like micro-angiopathy, increased blood-brain barrier permeability, and immune system changes exacerbate neuronal damage.
• Developmental increases in functional reserve enhance resilience in youth, while residual reserve aids recovery in the elderly.

Conclusions:

• Brain functional reserve is a key determinant of delirium risk, intensity, and recovery.
• Age-dependent structural brain changes significantly impact functional reserve, elevating delirium risk in older individuals.
• Understanding functional reserve is crucial for addressing delirium across the lifespan.