A Dutch study has found that those diagnosed with mild cognitive impairment (MCI) have a fourfold increased risk of developing dementia or Alzheimer’s disease (AD), and that stroke and other vascular damage are important risk factors.
The results of the study are published in a supplement to the Journal of Alzheimer’s Disease.
“Mild cognitive impairment has been identified as the transitional stage between normal aging and dementia,” said M. Arfan Ikram, M.D., Ph.D., a neuroepidemiologist at Erasmus University Medical Center (Rotterdam).
“Identifying persons at a higher risk of dementia could postpone or even prevent dementia by timely targeting modifiable risk factors.”
Unlike a clinical trial, the long-term, large-scale population-based study is an observational cohort study focusing on the general population, instead of persons referred to a memory clinic. It began in 1990, when almost 8,000 inhabitants of Rotterdam aged 55 years or older agreed to participate in the study.
Ten years later, another 3,000 individuals were added. Participants undergo home interviews and examinations every four years.
Several risk factors including older age, positive APOE-ɛ4 status, low total cholesterol levels, and stroke, as well as specific brain imaging data, were associated with an increased risk of developing MCI.
“This important prospective study adds to the accumulating evidence that strokes, presumably related to so called ‘vascular’ risk factors, also contribute to the appearance of dementia in Alzheimer’s disease,” said neurologist Amos D. Korczyn, M.D., of Tel Aviv University, guest editor of the supplement.
“The findings complement other emerging research that suggests middle-aged people should minimize their vascular risk factors,” he said.
“It should be remembered that delaying the onset of dementia by five years will reduce the prevalence of the disease by half. And of course, since there is no cure for AD, prevention is the best approach at present,” Korczyn said.
To be diagnosed with MCI in the study, individuals were required to meet three criteria: a self-reported awareness of having problems with memory or everyday functioning; deficits detected on a battery of cognitive tests; and no evidence of dementia.
They were categorized into those with memory problems (amnestic MCI) and those with normal memory (non-amnestic MCI).
Of 4,198 persons found to be eligible for the study, almost 10 percent were diagnosed with MCI. Of these, 163 had amnestic MCI and 254 had non-amnestic MCI. The risk of dementia was especially high for people with memory problems.
Similar results were observed regarding the risk for Alzheimer’s disease. Those with MCI also faced a somewhat higher risk of death.
The research team investigated possible determinants of MCI, considering factors such as age, APOE-ɛ status, waist circumference, hypertension, diabetes mellitus, total and HDL-cholesterol levels, smoking, and stroke.
Only older age, being an APOE-ɛ4 carrier, low total cholesterol levels, and stroke at baseline were associated with developing MCI.
Having the APOE-ɛ4 genotype and smoking were related only to amnestic MCI.
When the investigators analyzed MRI studies of the brain, they found that participants with MCI, particularly those with non-amnestic MCI, had larger white matter lesion volumes and worse microstructural integrity of normal-appearing white matter compared to controls.
They were also three times more likely than controls to have cavities in the basal ganglia or white matter. MCI was not associated with total brain volume, hippocampal volume, or cerebral microbleeds.
“Our results suggest that accumulating vascular damage plays a role in both amnestic and non-amnestic MCI,” said Ikram.
Researchers believe timely targeting of modifiable vascular risk factors, such as cholesterol levels, and stopping smoking, may help prevent MCI and dementia.
Source: IOS Press