Hippocampal and amygdalar atrophy are predictive of dementia in the cognitively intact elderly, Dutch researchers reported.
The investigators studied 511 community residents aged 60–90 years and free of dementia at baseline. The objective of the study, conducted by Dr. Tom den Heijer of Erasmus Medical Center in Rotterdam, the Netherlands, and his colleagues, was to assess whether atrophy of the hippocampus and amygdala was present before the onset of dementia. All of the participants were part of The Rotterdam Study, a prospective, population-based study launched in 1990.
In the current investigation, volumetric assessment of the hippocampus and amygdala was evaluated by MRI. The investigators also performed extensive neuropsychological testing and questioned participants about daily memory problems (Arch. Gen. Psychiatry 2006;63:57–62).
During a mean follow-up of 6 years, 35 of the participants developed dementia, 26 of whom were diagnosed with Alzheimer's disease. The investigators found that those participants who developed dementia had much smaller hippocampal and amygdalar volumes at baseline than did those without incident dementia.
Furthermore, they found that volume reduction at baseline was inversely associated with time until the onset of dementia. This was true “even in persons without memory complaints or low cognitive performance at baseline,” the investigators reported.
Dr. den Heijer and his colleagues said that MRI findings have been validated by previous autopsy studies of brain tissue showing neuronal loss and Alzheimer's disease.
Decreases in hippocampal and amygdalar volumes of 5%–17% were found, depending on how far in advance of dementia the MRI was done. For individuals with Alzheimer's disease, Dr. den Heijer's team found reductions ranging from 25% to 40%, a range that suggests that the atrophy rate accelerates in patients with Alzheimer's disease.
The investigators concluded that “structural imaging can help identify people at high risk for developing dementia, even before they have any memory complaints or measurable cognitive impairment.” They hastened to add, however, that most people with atrophy failed to develop dementia, even after 6 years.