Delirium and Its Relation to Cognitive Decline
Understanding Delirium as a Predictive Measure
Delirium has been utilized as a predictive measure for cognitive decline. However, recent research indicates that this correlation only holds true when delirium arises from the same pathological processes observed in classic dementia.
The Pathological Basis of Classic Dementia
Classic dementia is characterized by distinct pathological substrates, including amyloid plaques and neurofibrillary tangles. Amyloid plaques consist mainly of aggregated beta-amyloid proteins, derived from the amyloid precursor protein. Neurofibrillary tangles are formed by tau proteins, which play a crucial role in maintaining neuronal structure. Under normal circumstances, tau functions effectively when phosphate molecules are attached. However, when tau becomes over-phosphorylated, it results in tangles that cause protein dysfunction. Additionally, vascular lesions and Lewy bodies, which are protein aggregates in the brain, are also common indicators of classic dementia.
The Nature of Delirium
In contrast, delirium represents an acute brain dysfunction that significantly impairs mental processes, affecting at least 20% of elderly patients. This condition can stem from various causes, including infections, inflammation, or dehydration, and is not always tied to neurological issues. Previous studies have sought to determine whether a history of delirium could predict an inevitable increase in cognitive decline. However, the underlying pathology of delirium remains unclear, with possibilities that it may be independent of or interrelated to classic dementia processes.
Research on Delirium and Cognitive Decline
Currently, prior episodes of delirium are being considered as a predictive method for accelerated cognitive decline, though the relationship between the two is not fully understood. To investigate this association, Davis et al. conducted a study aimed at determining whether accelerated cognitive decline linked to delirium is independent of classic dementia-related factors.
Study Methodology and Findings
The researchers conducted three unselected population-based cohort studies, analyzing neuropathological autopsy data from 987 brain donors collected between January 1, 1985, and December 31, 2011, from prior dementia-delirium-related studies in Europe. The investigation focused on the presence of tangles, plaques, vascular lesions, and Lewy bodies in patients who experienced delirium, cognitive regression, or both.
The findings revealed that individuals who experienced delirium followed by cognitive decline had initially developed delirium due to the same pathological processes associated with classic dementia. Conversely, those who experienced delirium without subsequent cognitive decline had their condition triggered by factors not assessed in this study.
Conclusion
This study conclusively demonstrates that cognitive decline is only exacerbated by delirium when the delirium is linked to the pathologies of classic dementia.
Written By: Unaisa Bhayat, M.D. Candidate