A study by Tanis Ferman, PhD and colleagues at Mayo Clinic assessed the progression from mild cognitive impairment (MCI) to different forms of dementia. 337 people with mild cognitive impairment were followed for an average of five years with annual formal neurocognitive assessment. 116 did not progress to dementia; 49 progressed to dementia with Lewy bodies (DLB) and 162 progressed to Alzheimer’s disease (AD); 10 developed other forms of dementia.
Non-amnestic (non-memory) MCI progressed to DLB at a rate of 20 precent a year and to AD at a rate of two percent per year. Amnestic MCI progressed to AD at a rate of 17 percent per year and to DLB at a rate of two percent per year.
Patients with non-amnestic MCI were more likely to develop DLB than AD. Of those who progressed to DLB, 88 percent had mild impairment in one or both of two cognitive domains: attention or visuospatial skills. Although memory impairment was present in about a fourth of the MCI cohort who developed DLB, these patients also had attention and /or visuospatial deficits. Visual hallucinations were not seen at the MCI stage of DLB, but excessive daytime sleepiness, a history of dream enactment behavior during sleep and mild motor symptoms were common. Nearly all who progressed to Alzheimer’s had deficits in memory and no other cognitive domain.
Of those who came to autopsy, 76 percent of the clinically diagnosed DLB group had diffuse or transitional Lewy body disease (confirming the DLB diagnosis), while 80 percent of the clinically diagnosed AD group who came to autopsy had evidence of amyloid plaques and neurofibrillary tangles of AD. This research suggests that individuals with non-amnestic MCI (either attention or visuospatial difficulty) are 10 times more likely to progress to DLB, while individuals with amnestic MCI are more likely to develop AD.
This study was published in Neurology on February 12, 2013. Funding for the study was provided by the National Institutes of Health, the Mangurian Foundation and the Robert and Clarice Smith and Abigail Van Buren Alzheimer’s Disease Research Program.
Citation: Ferman TJ, Smith GE, Kantarci K, Boeve BF, Pankratz VS, Dickson DW, Graff-Radford NR, Wszolek Z, Van Gerpen J, Uitti R, Pedraza O, Murray ME, Aakre J, Parisi J, Knopman DS, Petersen RC. Nonamnestic mild cognitive impairment progresses to dementia with Lewy bodies. Neurology. 2013 Dec 3;81(23):2032-8.