Preventing Delirium among Older Adults with Dementia

Donna M. Fick, PhD, GCNS-BC, Associate Professor of Nursing, School of Nursing, Pennsylvania State University, University Park, PA, USA.
Ann Kolanowski, PhD, RN, FAAN, Elouise Ross Eberly Professor of Nursing, School of Nursing, Pennsylvania State University, University Park, PA, USA.

Delirium superimposed on dementia (DSD) is common, is associated with poor clinical and economic outcomes, and occurs across all settings of care. In this article, we briefly review outcomes of DSD, propose the idea of cognitive reserve as a possible mechanism for interventions that prevent and manage DSD, and present the evidence for delirium interventions. We conclude with implications for practice and suggest web-based resources for supporting best practices in the care of persons with DSD.
Key words: delirium, dementia, prevention, interventions, cognitive reserve.

Introduction
Delirium in persons with dementia is common, is associated with poor clinical and economic outcomes, and occurs across all settings of care. Delirium is superimposed on a dementia when an acute change in mental status (characterized by a fluctuating course, inattention, and either disorganized thinking or an altered level of consciousness) occurs in a patient with pre-existing dementia.¹ The pathogenesis of delirium is poorly understood, but is known to share several common features with dementia.²

The main risk factor for delirium is dementia. Delirium occurs in over half of hospitalized older adults with dementia and substantially worsens outcomes in a population already burdened with physical and mental losses.^2-4 In this article, we briefly review outcomes of delirium superimposed on dementia (DSD) and present the evidence and mechanisms for interventions to prevent and manage DSD. We conclude with implications for practice and web-based resources for best practices in the care of persons with DSD.

Outcomes of Delirium Superimposed on Dementia
Delirium often occurs in the hospital setting, but may occur even more frequently in community-living persons with dementia (PWD).³ The prevalence of DSD ranges from 22 to 89% in both hospital and community settings.⁴ Delirium superimposed on dementia accelerates the trajectory of functional decline and results in prolonged hospitalization, rehospitalization, premature placement in long-term care, death, and increased costs.^5-10 A recent US study found that the 1-year health care costs attributable to delirium varied from US$16,303 to US$64,421 per patient, with the national burden ranging from US$38 billion to US$152 billion each year.¹¹

Cognitive Reserve as a Mechanism for Preventing Delirium Superimposed on Dementia
While it has not yet been fully tested in delirium trials, one possible mechanism for delirium prevention in dementia may be the enhancement of cognitive reserve. Interventions that have the strongest links to improving cognitive reserve in PWD include physical activity, challenging mental activities, social interaction, and avoidance of anticholinergic and inappropriate medications. Most of the research on cognitive reserve has focused on its association with risk for dementia.¹³ Dementia and delirium, however, share common clinical, metabolic, and cellular mechanisms that lead to reduced cognitive reserve, suggesting that they may represent points along a continuum.²

The enhancement of cognitive reserve is a mechanism that may modify risk for the clinical expression of brain disease. Cognitive reserve includes both passive and active brain processes that are protective of disease manifestation. Brain size and synapse density prior to disease onset¹² and life-long engagement in mentally stimulating activities such as formal educational and complex occupational and leisure activities¹³ may explain why individuals with the same