"We used an objective, gold-standard measure of fitness which hadn't been assessed in Alzheimer's patients yet, cardiorespiratory fitness, or VO2 peak, where we basically measure how much work someone is capable of doing," Burns explained.
Participants walked on a treadmill while their oxygen consumption was measured. "At their peak, how much oxygen they're consuming is a measure of how physically fit they are," Burns said.
MRI scans measured brain atrophy.
The VO2 peak was slightly lower in people with Alzheimer's compared to controls. And individuals with Alzheimer's who were less physically fit had quadruple the amount of brain shrinkage compared to normal older adults.
"The people with higher fitness levels had larger brains, and there was a strong correlation between the two," Burns explained. "We're limited because of the study design, but it could suggest that maintaining fitness may have a beneficial effect on the Alzheimer's disease process."
"We didn't find fitness to be associated clearly with cognitive performance, but that may be, because we need to study more people or the cognitive performance measures may not be sensitive enough," he added.
The study pointed to three possible explanations for the relationship: cardiorespiratory fitness affects brain atrophy related to Alzheimer's disease; the Alzheimer's disease process affects fitness; or some other, as-yet-unknown factor underlies both Alzheimer's-related brain atrophy and physical fitness.
"We're designing a study where we try to establish the cause and effect," Burns said. "Can we use exercise to enhance fitness in Alzheimer's disease and, by doing that, will it affect disease progression?"
The Alzheimer's Association's Maintain Your Brain program
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