Visual hallucinations are a core feature of dementia with Lewy bodies, occurring in 32 to 85 percent of autopsy-confirmed cases. Individuals with Alzheimer’s disease also experience hallucinations, though to a lesser degree and typically later in the course of the disease. New research reveals the onset of visual hallucinations within 5 years of developing dementia increases the odds of pathology-confirmed Lewy body disease 4-5 times over Alzheimer’s disease.
Research led by Tanis J. Ferman, Ph.D., associate professor at Mayo Clinic in Jacksonville, FL, studied brain tissue samples of autopsied individuals with a well-documented history of dementia, and who had died within the last 3 years. This included 41individuals with autopsy-confirmed pathologic Lewy body disease (LBD), 70 individuals with autopsy-confirmed Alzheimer’s disease (AD) and 14 individuals with Alzheimer’s disease and amygdala-predominant Lewy bodies (AD-ALB). Samples were also categorized by density of Alzheimer’s and/or Lewy body pathology using Braak staging. Questionnaires were sent to the next-of-kin, to learn at what age the person’s dementia started and the approximate onset of any visual hallucinations, misperceptions and misidentification of family members during the life of the person with dementia.
People in the LBD group lived with dementia for fewer years than the AD and AD-ALB groups, with an average of 9 years, compared to 11 and 14 years, while the estimated age of onset did not differ between the groups. Although there was no difference in the presence or absence of visual hallucinations among any of the groups in this study sample, the point of hallucination onset was earlier in the dementia course in LBD than AD or AD-ALB. There was no difference noted in the types of visual hallucinations experience, with people and animals being the most common hallucinated images in all three groups.
Using logistic regression modeling, researchers determined that if visual hallucinations developed at any time during dementia, the likelihood of pathology-confirmed LBD was 1.5 to 2 times greater than Alzheimer’s. Even more strikingly, if the hallucinations began within the first 5 years of dementia, that likelihood of autopsy-confirmed LBD was 4 to 5 times higher than AD or AD-ALB. Earlier onset of visual hallucinations was associated with greater Lewy body density in the LBD group and greater density of neurofibrillary tangles of Alzheimer’s disease in the AD/ALB groups.
Visual misperceptions occurred across all 3 diagnostic groups, while family misidentification was disproportionally more common in the AD-ALB group. A common type of family misidentifications in LBD is called Capgras syndrome, the belief that a relative is a duplicate or imposter. In Alzheimer’s disease, it is more common that the person believes that one relative is actually a different relative, such as an adult child mistaken for a parent. As with visual hallucinations, in LBD there was a significantly earlier onset of misperceptions and family misidentifications compared to AD and AD-ALB.
This research provides insights into the importance of the timing of visual hallucinations, misperceptions and family misidentification in the differential diagnosis of dementia. In particular, the development of visual hallucinations within the first 5 years of the dementia, is more likely to represent Lewy body dementia than Alzheimer’s disease. This has implications for a clinician’s ability to accurately diagnose these conditions earlier in the disease course.
This study was first published in Parkinsonism and Related Disorders in February, 2013. Authors in this paper who are on the Lewy Body Dementia Association’s Scientific Advisory Council include Tanis J. Ferman, Ph.D. and Dennis W. Dickson, M.D.