This document reviews the association between delirium and dementia in elderly people. It discusses delirium and dementia diagnosis, dementia as a risk factor for delirium, and delirium as a risk factor for dementia. Dementia increases the risk of delirium by 2-5 times. Patients with dementia who experience delirium have worse outcomes, including higher mortality and institutionalization rates. Delirium may also cause permanent neuronal damage and lead to the development or worsening of dementia.

1. REVIEW OF ASSOCIATION BETWEEN DELIRIUM AND DEMENTIA
IN ELDERLY PEOPLE
Rita Pereira2, Sónia Martins1,2, Lia Fernandes1,2,3
1Center for Health Technology and Services Research/CINTESIS and 2Faculty of Medicine, University of Porto.
3Clinic of Psychiatry and Mental Health, CHSJ, Porto - Portugal
RESULTSBACKGROUND
REFERENCES
METHODS
This is a narrative literature
review of recent articles,
particularly of systematic
reviews, published in electronic-
based journals and focused on
the relationship between
delirium and dementia.
This review will describe and
discuss the state of the art about
this specific topic, considering
the following topics:
 Delirium and dementia:
differential diagnosis
 Dementia as a risk factor for
delirium
 Delirium as a risk factor for
dementia.
AIM
DISCUSSION AND CONCLUSION
Copyright © 2017, Rita Pereira, Sónia Martins, Lia Fernandes Contact: Lia Fernandes lfernandes@med.up.ptNo potential conflict of interest.
Delirium is a neuropsychiatric
syndrome, characterised by an
acute change in mental status
with a fluctuating course of
symptoms [1], that affects
almost 50% of people aged 65
years or older, admitted to
hospital [1-2].
Delirium is associated with
negative outcomes, including
increased risk of mortality,
cognitive decline [1].
In 50% of the cases, the cause of
delirium is multifactorial,
resulting from a complex inter-
relationship between several
predisposing factors (e.g.
dementia) in highly vulnerable
patients that are exposed to
precipitating factors (e.g.
infections) [1-3].
There is an interrelation between
delirium and dementia. Delirium
could be a marker of
vulnerability to dementia, might
unmask dementia, or might
itself leads to dementia [4].
This review aims to highlight
the association between
delirium and dementia in
elderly people, focusing on
diagnosis, pathophysiology,
prevention, and management.
DEMENTIAAS A RISK FACTOR FOR DELIRIUM
Several studies [7-14] identified cognitive impairment and dementia as important risk factors for delirium, increasing
its risk by two to five times, associated with worse outcomes (Table 2).
Table 2 – Studies about dementia as risk factor for delirium and dementia
The underlying brain vulnerability of these patients with dementia may predispose to the development of delirium, as
a consequence of insults related to the acute medical disease, medication or environmental factors. The systemic
inflammatory insult triggers a cholinergic depletion, which seems to lead to the development of acute cognitive
deficits. In the presence of neurodegenerative disease, the cholinergic inhibition is reduced, resulting in an
exaggerated inflammatory cascade that furthers delirium [7-14].
DELIRIUM AS A RISK FACTOR FOR DEMENTIA
Delirium may cause permanent neuronal damage, which may lead to the development or worsening of a pre-existing
dementia [15-22].
Table 2 – Studies about dementia as risk factor for delirium and dementia
Delirium and dementia frequently coexist, which
could challenge differential diagnosis. Several
studies identified delirium in patients with
baseline cognitive impairment and/or dementia.
The prevalence ranges from 22 to 89% in both
hospital and community settings [5-6].
Distinguishing both conditions can be difficult
since these two syndromes have substantial
overlapping features. However, several signs and
symptoms can be used to distinguish delirium
from dementia [1, 4-6]. Most prominently, the
onset of delirium is typically abrupt with a
duration of hours to days, while the onset of
dementia is insidious and progressive, over
months to years. In delirium, attention and level of
consciousness are reduced and fluctuating. In
dementia, these cognitive domains typically
remain intact until the advanced stages (Table 1).
The identification of risk factors for delirium, specifically pre-existing cognitive impairment or dementia, in elderly
people admitted to hospital is essential to the implementation of preventive strategies that may contribute to the
decrease of delirium rates. This is based on the results of the follow-up studies demonstrating that patients with
dementia who develop delirium have worse outomes than those with dementia alone, in particular with higher rates of
hopitalization readmission, mortality, institutionalisation and worsening of cognitive decline.
DELIRIUM DEMENTIA
Onset Abrupt Insidious
Duration Hours, days, months Months to years
Course Fluctuating Chronic, progressive
(except for DLB)
Attention Impaired Normal
(except in severe dementia)
Consciousness Altered Alert
Memory Impaired Impaired
Speech Incoherent, slow, or rapid Coherent (anomia or aphasia
may occur)
Thinking Disorganized or incoherent Impoverished and vague
Cause Underlying medical condition,
substance intoxication,
iatrogenic event
Underlying neurological
process
Studies Main findings
Koster et al 2013 [7]
A new risk model was constructed with the following risk factors: a higher Euroscore, older age (≥70 years), cognitive
impairment, number of comorbidities, history of delirium, alcohol use and type of surgery
Bo et al 2009 [8] Acute geriatric ward hospitalization is associated with less incident delirium among older medical inpatients
Rudolph et al 2009 [9]
Multivariable analysis identified 4 variables independently associated with delirium: prior stroke or transient ischemic attack,
Mini Mental State Examination score, abnormal serum albumin, and the Geriatric Depression Scale.
Kalisvaart et al 2006 [10] Cognitive impairment, age, and type of admission are important risk factors for delirium in this surgical population.
Wilson et al 2005 [11] Pre-admission cognitive deterioration and depression were identified as risk factors for developing subsequent delirium.
O’Keeffe et al 1996 [12]
Delirium was associated with increased of length of stay, decreased activity of daily living function, and nursing home even after
controlling for dementia
Pompei et al 1994 [13] Dementia has been identified as a risk factor for delirium in medical, surgical and psychiatric patients.
Inouye et al 1993 [14]
Four independent baseline risk factors for delirium were identified: vision impairment; severe illness; cognitive impairment and a
high blood urea nitrogen/creatinine ratio
Main findings
Cognitive function and
ageing study 2014 [15]
Study-defined delirium was associated with a new dementia diagnosis at two years and death, even after adjustment for acute illness severity
BRA IN-ICU 2013 [16] A longer duration of delirium in the hospital was associated with worse global cognition and executive function scores at 3 and 12 months
Gross et al 2012 [17] Delirium is highly prevalent among persons with Alzheimer Disease who are hospitalized and is associated with an increased rate of
cognitive deterioration that is maintained for up to 5 years
Saczynski et al 2012 [18] Delirium is associated with a significant decline in cognitive ability during the first year after cardiac surgery, with a trajectory characterized
by an initial decline and prolonged impairment.
Vantaa 85+ 2012 [19] Delirium is a strong risk factor for incident dementia and cognitive decline in the oldest-old
Fong et al 2009 [20] Delirium can accelerate the trajectory of cognitive decline in patients with Alzheimer disease
Bickel et al 2008 [21] Delirium predicts a future cognitive decline with an increased risk of dementia
Lundstrom et al 2003 [22] Delirium in nondemented femoral neck fracture patients is associated with the development of dementia and a higher mortality
DELIRIUM AND DEMENTIA: DIFFERENTIAL DIAGNOSIS
Table 1- Differential diagnoses of delirium and dementia
References
This work is supported by FCT Post-Doctoral fellowship (SFRH/BPD/103306/2014), by FEDER through the operation POCI-01-0145-FEDER-
007746 funded by the Programa Operacional Competitividade e Internacionalização – COMPETE2020 and by National Funds through FCT -
Fundação para a Ciência e a Tecnologia within CINTESIS, R&D Unit (reference UID/IC/4255/2013)
[1] Inouye et al. The Lancet, 2014, 383(9920), 911-922. [2]
Barbara et al. Clinical Medicine, 2014, 14(2):192–5 [3] Ryan et al.
BMJ Open 2013;3:e001772. [4] Tamara et al. Lancet Neurol 2015;
14: 823–32; [5] Fick et al. J Am Geriatr Soc 50:1723-1732,
2002.[6] Fick et al. J Gerontol Nurs, 2009 Mar;35(3):30-8; [7]
Koster et al. Eur J Cardiovasc Nurs 2013; 12: 284–92; [8] Bo et al.
Am J Geriatr Psychiatry 2009; 17: 760–68; [9] Rudolph et al.
Circulation 2009; 119: 229–36; [10] Kalisvaart et al. J Am Geriatr
Soc 2006; 54: 817–22; [11] Wilson et al. Int J Geriatr Psychiatry
2005; 20: 154–59; [12] O’Keeff et al. Age Ageing 1996; 25: 317–
21; [13] Pompei et al. J Am Geriatr Soc 1994; 42: 809–15; [14]
Inouye et al. Ann Intern Med 1993;119: 474–81; [15] Davis et al.
BMC Geriatr 2014; 14: 87; [16] Pandharipande et al. N Engl J
Med 2013; 369: 1306–16; [17] Gross et al. Arch Intern Med 2012;
172: 1324–31; [18] Saczynski et al. N Engl J Med 2012; 367: 30–
39; [19] Davis et al. Brain 2012; 135: 2809–16; [20] Fong et al.
Neurology 2009; 72: 1570–75; [21] Bickel et al. Dement Geriatr
Cogn Disord 2008; 26: 26–31; [22] Lundstrom et al. J Am Geriatr
Soc 2003; 51: 1002–06