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Delirium increases cognitive decline in dementia

Cognitive decline was greater among individuals with delirium and pathologic processes of dementia than those with delirium or dementia individually, according to recent findings.

“Although delirium is now established as a strong predictor of cognitive decline in older adults, whether it accounts for additional, interrelated, or unexplained pathologic injury that contributes to dementia has not previously been examined,” Daniel H. J. Davis, PhD, MRCP, of the University of Cambridge, and colleagues wrote. “It is possible that when dementia follows delirium it has a different pathologic profile compared with dementia that develops without delirium. Therefore, understanding how delirium affects the evolution of dementia in the context of a particular burden of pathologic findings may offer new insights into independent mechanisms that explain cognitive decline after delirium.”

To examine associations between delirium and cognitive decline in late life, researchers analyzed harmonized data from three observational studies for 987 individual brain donors. Studies had a median follow-up of 5.2 years until death. Mean age at death was 90 years.

Overall, 279 participants had delirium and of these, 75% were women.

Six years before death, study participants had a mean Mini-Mental State Examination (MMSE) score of 24.7 points.

Participants with delirium had poorer initial MMSE scores, compared with those without delirium (–2.8 points; 95% CI, –4.5 to –1; P < .001).

Cognitive decline attributable to delirium accounted for –0.37 MMSE points per year (P < .001).

Cognitive decline attributable to pathologic processes of dementia accounted for –0.39 MMSE points per year (P < .001).

The combination of delirium and pathologic processes of dementia caused the greatest cognitive decline, with an additional –0.16 MMSE points per year (P = .01).

Analysis indicated MMSE scores among participants with delirium and pathologic processes of dementia declined by 0.72 points per year more than those without the disorders.

“The findings in this study highlight that cognitive decline after delirium is not simply acceleration of underlying dementia pathologic processes; rather, there is a synergistic effect of delirium and dementia on the rate of cognitive decline,” Tamara G. Fong, MD, PhD, of Harvard Medical School, and colleagues wrote in an accompanying editorial. “Identifying preventable factors that lead to neuronal injury in delirium and pharmacologic and nonpharmacologic strategies to target such factors is critical. This study, by showing the potential for delirium mediating its effects on cognitive decline independent of classic dementia pathologic processes, lays the important foundation for this future work.” – by Amanda Oldt

Disclosure: Davis and Fong report no relevant financial disclosures. Please see the study for a full list of relevant financial disclosures.