The inter-relationship between delirium and dementia: the importance of delirium prevention

Abstract

Delirium and dementia are two frequent causes of cognitive impairment among older adults and have a distinct, complex and interconnected relationship. Delirium is an acute confusional state characterized by inattention, cognitive dysfunction and an altered level of consciousness, whereas dementia is an insidious, chronic and progressive loss of a previously acquired cognitive ability. People with dementia have a higher risk of developing delirium than the general population, and the occurrence of delirium is an independent risk factor for subsequent development of dementia. Furthermore, delirium in individuals with dementia can accelerate the trajectory of the underlying cognitive decline. Delirium prevention strategies can reduce the incidence of delirium and associated adverse outcomes, including falls and functional decline. Therefore, delirium might represent a modifiable risk factor for dementia, and interventions that prevent or minimize delirium might also reduce or prevent long-term cognitive impairment. Additionally, understanding the pathophysiology of delirium and the connection between delirium and dementia might ultimately lead to additional treatments for both conditions. In this Review, we explore mechanisms that might be common to both delirium and dementia by reviewing evidence on shared biomarkers, and we discuss the importance of delirium recognition and prevention in people with dementia.

Fig. 1. A hypothetical model for the inter-relationship between delirium and dementia and potential opportunities for prevention.

a,b | In the setting of precipitating factors, such as hypoxia, metabolic abnormalities, medications, infection or surgery, and in the presence of an existing vulnerability, such as Alzheimer disease (AD) or other neurodegenerative pathology, cerebrovascular disease, or injury, delirium (green) can occur. Alternatively, owing to the presence of resilience factors, such as cognitive reserve, or the implementation of prevention strategies (grey) to minimize one or more modifiable delirium risk factors, delirium does not occur (red). c | The development of delirium and subsequent neuroinflammation might then result in the acceleration of underlying neurodegenerative pathology. Alternatively, in individuals without underlying neurodegenerative pathology, delirium might be associated with neuronal injury, with ‘de novo’ mechanisms leading to dementia.