What Is the Prevalence of Hallucinations and Delusions Associated With Dementia-related Psychosis?

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Hello. This presentation will highlight the prevalence of dementia-related hallucinations and delusions across the various dementia types.

I’m Dr. Ara Khachaturian, a senior research fellow at the National Supercomputing Institute of the University of Nevada in Las Vegas.

Please note that this disease-awareness, non-CME program is intended only for healthcare professionals involved in the management of people with dementia-related hallucinations and delusions. It is sponsored by Acadia Pharmaceuticals Inc., and I’m presenting on behalf of Acadia as a paid consultant. This presentation is not meant to discuss specific treatment options for dementia-related psychosis.

Dementia is a syndrome: It is a recognizable constellation of symptoms and signs that may reflect any of several underlying pathogenetic processes or causes that affect the structural and functional integrity of the brain.1

Dementia is common in older adults in the United States, with approximately 7.9 million people living with dementia, of whom 3.95 million carry a diagnosis of at least 1 type of dementia.1-3

The most common type of dementia in the United States is Alzheimer’s disease.1-4 Vascular dementia is the next most common, followed by dementia with Lewy bodies and Parkinson’s dementia.6,7 Frontotemporal dementia is the most rare. It occurs in about 1% of all individuals with dementia in the United States.2

It is interesting to note that, while we tend to think about prevalence rates in terms of individual dementia types, postmortem pathology data from 2 large databases indicate that more than half of individuals with dementia had mixed neuropathologies.8 In the study shown here, Brenowitz and colleagues examined data from the National Alzheimer’s Coordinating Center, or NACC, and the Adult Changes in Thought, or ACT, study and found a large degree of overlap in Alzheimer’s disease neuropathologic change, Lewy body disease, and vascular brain injury in both samples, regardless of age at death.8 More than half of individuals with dementia—or 59% of NACC participants and 68% of ACT participants—had mixed neuropathologies, defined as Alzheimer’s disease neuropathologic change plus Lewy body disease or vascular brain injury.8

According to a survey, the prevalence of dementia increases as people age. These data are from the 2015 National Health and Aging Trends Study, or NHATS, a longitudinal US population-based survey of community-dwelling individuals aged 65 years and older who were considered to have probable dementia, according to the NHATS dementia classification. Per this classification, participants must have met at least 1 of the following criteria: 1) had a diagnosis of dementia or Alzheimer’s disease; 2) met the AD8 criteria (administered to proxy) if there was no diagnosis reported; and 3) had scores at least 1.5 standard deviations below the mean of self-respondents in at least 2 of the following domains: orientation, memory, or executive functioning.9

When we take a closer look at the most common type of dementia—Alzheimer’s dementia—the number of older people with this disease is projected to nearly triple from 4.7 million to 13.8 million by 2050.4,10 The growing number of new cases represents a key challenge for society: How do we manage the care of people with dementia? The answer to this question becomes more complex when we consider that dementia is more than cognition.

Neuropsychiatric symptoms are a common feature across the dementias, and their onset can occur at various times in the course of illness. These symptoms include delusions, hallucinations, agitation/aggression, dysphoria, anxiety, euphoria, apathy, disinhibition, irritability/lability, and aberrant motor activity.11

Among older people with dementia living in long-term care facilities, 79% have at least 1 clinically significant neuropsychiatric symptom, which is defined as having a Neuropsychiatric Inventory—or NPI—score of 4 or higher.12 Among older community-dwelling adults with dementia, the cumulative 5-year prevalence of at least 1 neuropsychiatric symptom is 97%.13

A study by Jost and colleagues that examined individuals with Alzheimer’s disease specifically documented the onset times of frequently occurring psychiatric symptoms. Some of these, such as depression, paranoia, and anxiety, occurred early in the course of the disease, as in before the diagnosis of dementia. On the other hand, symptoms, such as irritability, hallucinations and delusions, and agitation and aggression, were documented within 2 years, on average, after the diagnosis.14

When we look specifically at the symptoms of hallucinations and delusions, we find that they are prevalent across the dementias. We have seen previously how the number of individuals with various dementias adds up to approximately 7.9 million. Although the rates of hallucinations and delusions vary based on dementia type, approximately 2.4 million people in the United States have dementia-related hallucinations and delusions.15-29 The prevalence rates of hallucinations and delusions by dementia type are shown here. As healthcare professionals, it is important to be able to identify hallucinations and delusions in our patients with dementia.

A hallucination is a perception-like experience that occurs without an external stimulus and is sensory in nature. Patients may see, hear, smell, taste, or feel something that is not there.30,31

A delusion is a false, fixed belief despite evidence to the contrary. For example, a patient may think that a family member is stealing from him or her or that the police are following him or her. A suspicious delusion is sometimes referred to as paranoia.30,31

Ballard and colleagues estimated the frequency and phenomenology of hallucinations and delusions in 124 people aged 65 years or older diagnosed with mild or moderate dementia of any type.23 The most common hallucinations, with a frequency of more than 5% to 20% were second-person auditory hallucinations, visual hallucinations of animals or insects, and visual hallucinations of relatives in the house.23 The most common delusions, with a frequency of more than 20% to 25%, were delusions of reference, theft or possessions being hidden, and strangers in the house.23

Dementia-related hallucinations and delusions occur episodically and may persist. The same study by Ballard and colleagues found that most older adults with dementia experienced psychotic symptoms 2 to 6 times per week.23

A study of 181 patients with Alzheimer’s disease found that hallucinations and delusions were episodic, meaning that they tended to come and go over time, such that cross-sectional observations of the frequency of symptoms ranging from 12% to 25% at any visit tended to underestimate the 1-year frequency rate of 36% in this population.32

Although the persistence of hallucinations and delusions beyond 3 months was mostly below 30%, in some studies, hallucinations persisted beyond 3 months in up to 52% of patients, and delusions persisted for that period in up to 82% of patients.33

In a study of community-dwelling adults aged 65 years or older, 408 people with newly identified dementia were followed for up to 5 years.13 The proportion of older adults with newly identified dementia who experienced hallucinations or delusions approximately doubled over 5 years.13 The point prevalence of hallucinations increased from 10% at baseline to 19% to 24% at all subsequent visits, with an overall 5-year period prevalence of hallucinations of approximately 40%.13 The point prevalence of delusions increased from 18% at baseline to 34% to 38% during the last 3 follow-up visits. Approximately 60% of patients experienced delusions at some point during the 5-year period.13

In people with dementia-related hallucinations and delusions, the association between these symptoms and episodes of aggression is complex. Some studies have found that delusions and—to a lesser degree—hallucinations may be associated with aggression in Alzheimer’s dementia.22,34,35

In a study of 270 outpatients with probable Alzheimer’s disease by Gilley et al, at baseline, hallucinations were reported in 99 participants and delusions in 128 participants. The presence of delusions increased the relative risk of physical aggression 2.8-fold after controlling for dementia severity and previous episodes of aggression. However, hallucinations did not increase the relative risk of physical aggression in this study.34

In a cross-sectional study of the relationship between psychiatric syndromes and dementia severity, 1155 people diagnosed with probable Alzheimer’s disease were assessed using multiple established scales, and 468 were found to have had hallucinations or delusions. In moderate or severe stages of Alzheimer’s disease, hallucinations and delusions were associated with an increased odds of aggression.22

In another cross-sectional study of more than 100,000 nursing home residents across 5 states, Leonard and colleagues sought to identify modifiable characteristics, including hallucinations and delusions, associated with physical or verbal aggression in residents aged 60 years or older with dementia. Among these residents, 7120 were reported to have been aggressive in the week prior to their annual comprehensive health assessment, of whom 1002 had hallucinations or delusions. The presence of hallucinations and delusions significantly increased the odds of physical aggression among nursing home residents with dementia after adjusting for potential confounders, such as age, gender, and severity of cognitive impairment. Depression had the highest odds of physical aggression.35

In conclusion, hallucinations and delusions are prevalent across the dementias, and the onset of these and other neuropsychiatric symptoms can occur at various times in the course of the illness. Symptoms of dementia-related hallucinations and delusions occur episodically, and the nature and duration of episodes vary between patients and across dementia types. Hallucinations and delusions may be associated with the risk of aggression in some patients with dementia, although more research is needed to better understand the potential relationship.

Thank you again for joining me for this presentation.


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University of Nevada, Las Vegas
Las Vegas, NV

Faculty Insights

There is a substantial need to increase society’s awareness of the neuropsychiatric symptoms of dementia.

–Ara S. Khachaturian, PhD