The study analyzed 223 patients with dementia, who were seen at an outpatient memory clinic and diagnosed with AD or VaD. Participants were evaluated by a team of dementia specialists and underwent neuropsychological testing, appropriate brain scans, and necessary blood tests.
What the researchers found is that dementia patients thought to be suffering from either AD or VaD could be sorted into distinct, very nuanced clinical profiles. Using latent class analysis, the researchers were able to identify four distinct groups:
- Moderate/mixed dementia group
- Mild/mixed dementia group
- Dysexecutive group with significant impairment in multitasking
- Amnestic group with profound memory loss
Follow-up analyses comparing these four groups on neuropsychological measures that delved deeper into the process and errors produced on neuropsychological tests showed that the dysexecutive group exhibited marked difficulty sustaining attention and concentration. The moderate/mixed group evidenced pronounced and greater impairment on language-related tests compared to other neuropsychological abilities. Amnestic patients were clearly distinguished by severe memory problems, but less impaired on other neuropsychological tests. Mild/mixed patients exhibited milder memory deficits that were intermediary between the amnestic and moderate/mixed groups.
"Through this study we were able to determine that these two common forms of dementia are not wholly separate," said David J. Libon, PhD, the study's lead investigator and a professor in the Department of Neurology. "These shared characteristics should be taken into consideration both in the development of future AD and VaD diagnostic guidelines and in selecting patients for newly emerging medicine designed to treat dementia". Libon went on to say that the heterogeneity seen in this research could be one reason why virtually all clinical trials designed to treat Alzheimer's disease and related conditions have been so disappointing.
In addition to Dr. Libon, the study's research team consisted of: Deborah Drabick, PhD, and Tania Giovannetti, PhD, both from the Department of Psychology at Temple University; Catherine Price, PhD, Department of Clinical and Health Psychology, University of Florida; Mark Bondi, PhD, and Lisa Delano-Wood, PhD, both from the Department of Psychiatry, University of California San Diego and the Psychology Service VA San Diego Healthcare System; Melissa Lamar, PhD, Department of Psychiatry, University of Illinois; Daniel Nation, PhD, Department of Psychology, University of Southern California; Rhoda Au, PhD, Department of Neurology, Boston University and the Framingham Heart Study; Rod Swenson, PhD, Department of Neuroscience, North Dakota Medical School; Laura Brennan, PhD, Joel Eppig, BA, and Christine Nieves, BA, all three from the Department of Neurology at Drexel University College of Medicine; and Kathryn Devlin, BA, Department of Psychology at Temple University.