White matter hyperintensity volume may predict one-year cognitive decline among healthy persons.
Despite healthy, active lifestyles, many older adults may have silent vascular disease detectable on brain scans that can affect their ability to think, according to research published in the November Archives of Neurology.
“This study shows that silent vascular disease is really common as we get older and it influences our thinking abilities,” said Charles DeCarli, MD, Professor of Neurology in the School of Medicine at the University of California Davis and Director of the UC Davis Alzheimer’s Disease Center. “We’re beginning to realize that vascular disease plays a major role in Alzheimer’s disease—they go together.”
The study findings are based on data from a convenience sample of participants in the Alzheimer’s Disease Neuroimaging Initiative. The initiative assesses individuals who are cognitively normal, those who have mild cognitive impairment (MCI), and those with Alzheimer’s disease using MRI and PET scanning, laboratory testing, and cognitive testing to track changes in their cognitive status. The purpose of the study was to better understand the relationship between white matter hyperintensities and the extent to which they precede, coincide with, or follow short-term changes in cognitive functioning.
A total of 804 participants ages 55 to 90 were recruited from more than 50 research sites throughout the US and Canada. Approximately 200 were cognitively normal, and about 400 had signs of MCI. These participants were followed for three years. An additional 200 participants with Alzheimer’s disease were followed for two years.
All of the participants’ baseline cognitive functioning was established using clinical diagnostic evaluation, including the Mini Mental State Exam (MMSE) and the Alzheimer’s Disease Assessment Scale–Cognitive Subscale (ADAS–Cog). Criteria for the normal group included no evidence of depression, MCI, or dementia. Participants were classified as having MCI if they had a subjective memory complaint or objective memory loss, among other measures. Patients with Alzheimer’s disease met nationally accepted criteria for probable Alzheimer’s disease.
A Correlation Revealed
Participants whose white matter hyperintensities were significantly above average at study entry lost more points each year in cognitive testing than did those whose white matter hyperintensities were average at baseline. Those with MCI or Alzheimer’s disease at baseline had additional declines on their cognitive testing each year, meaning that the presence of white matter hyperintensities and MCI or Alzheimer’s disease together added up to even faster and steeper cognitive decline. Participants who were older at baseline saw faster declines over time in MMSE scores.
An Important Predictor of Cognitive Decline
At the outset of the study, the extent of white matter hyperintensities was associated with greater subsequent declines in global cognition during a one-year period, the researchers reported. “In a model that controlled for baseline age, apolipoprotein E genotype, clinical diagnosis, cardiovascular risks, and other relevant covariates, white matter hyperintensity volume at baseline was significantly associated with greater subsequent declines in global cognition over one year,” the research team wrote. “The finding is significant because it suggests that, even in a sample that was intentionally designed to mimic a clinical trial, with frequent evaluations, short-term follow-up, and a relatively mild profile of cardiovascular risk, white matter disease may be an important predictor of subsequent short-term global cognitive change.”