Higher levels of physical fitness may preserve brain volume in the early clinical stages of Alzheimer's disease, new study findings suggest.
"In normal aging, physical fitness appears to mitigate functional and structural age-related brain changes," Dr. Jeffrey M. Burns and colleagues write in the July 15 issue of Neurology. "Whether this is observed in Alzheimer's disease is not known."
To investigate, Dr. Burns at the University of Kansas School of Medicine in Kansas City and his associates determined peak oxygen consumption (VO2-peak) as a measure of cardiorespiratory fitness in a cohort of 57 patients with early-stage Alzheimer's disease and 64 control subjects without dementia. Brain volume was determined by MRI.
As measured by symptom-limited graded treadmill testing, VO2-peak was "modestly" higher in the control group (38.1 vs 34.7 mL/kg/min, p = 0.002), their report indicates.
In the Alzheimer group, VO2-peak was significantly associated with whole brain volume (p < 0.001). The association remained after controlling for age, sex, severity of dementia, physical activity, and physical frailty.
Although whole brain volume was associated with global cognitive performance and Mini-Mental State Examination score in the dementia group, the investigators observed no significant association between dementia severity and VO2-peak.
There were no significant associations between VO2-peak and brain volume or cognitive performance in the control group.
"Our data are consistent with, but do not establish, cardiorespiratory fitness as a moderating factor in neurodegeneration," the investigators maintain. It's also possible, they say, that a common underlying disease-related process may impact both brain atrophy and cardiorespiratory fitness in subjects with early Alzheimer's disease.
Even though they could not determine causation, Dr. Burns told Reuters Health that he "definitely" would encourage physicians to recommend appropriate physical exercise to patients with Alzheimer disease.
"I recommend that all my Alzheimer's patients stay both physically and mentally active, even though proof is lacking that these activities clearly influence disease progression," he said. "There are exercise benefits for general health as well as for depressive symptoms that can be achieved with physical exercise in people with dementia."
"There are two important points that motivate research like ours," he continued. "First, we need proof that exercise and physical fitness cause a modification of the disease process and then determine what mechanism is mediating that effect."
"Second, if exercise is a disease-modifying therapy for AD, we are doing a very poor job of fully utilizing it as a therapy. Thus, more evidence is necessary to demonstrate this, which in turn will stimulate the development of programs and delivery systems that will encourage people with dementia to exercise and, more importantly, sustain that behavior."
With those goals in mind, Dr. Burns' group will continue to follow this same cohort over two years to see how fitness predicts change over time in cognition and brain structure.
"We are also planning a large randomized controlled trial of various types of exercise in AD to assess the cause-and-effect relationship of exercise (and enhanced cardiorespiratory fitness) on AD progression," Dr. Burns said.
Neurology 2008;71:210-216
