If you want to keep your brain healthy as you age, exercise your body. That, in essence, is the conclusion of four clinical trials, the results of which were reported at the Alzheimer's Association International Conference in Vancouver, British Columbia, early last month.
The most ambitious study, of 120 sedentary senior citizens, was conducted at the University of Pittsburgh. Walking for exercise slows the memory loss associated with Alzheimer's, report researchers headed by psychology professor Kirk Erickson, Ph.D.
One group of seniors in the study walked for 30 to 45 minutes three days a week. The other just stretched and toned.
After a year, the walkers increased the size of their hippocampus, the region of the brain associated with memory, by 2 percent, as measured with MRIs. Most Alzheimer's patients suffer significant shrinking of the hippocampus.
The Pitt researchers also found growth in the prefrontal cortex, the region of the brain associated with decision making and related activities psychologists call executive function. The more fit the patient, the larger the growth in the prefrontal cortex.
"I would say this is pretty dramatic," Mr. Erickson said. "This is only after one year of exercise and moderate intensity at that."
Though it's clear moderate exercise can reduce the risk of cognitive impairment in older adults, very little is known yet about why exercise is good for brain health, or, what, exactly, is the relationship between a larger hippocampus and better memory, he said.
In a six-month study of women ages 70 to 80, researchers at the University of British Columbia in Vancouver found that walking and resistance training (lifting weights) improved significantly performance on the Stroop Test, which measures a person's ability to sustain attention with and without interference. It's commonly used to measure the brain's vitality and flexibility. Only the weight lifters had positive changes in the brain regions associated with memory.
"Twice-weekly resistance training is a promising strategy to alter the trajectory of cognitive decline in seniors with MCI [mild cognitive impairment]," said Teresa Liu-Ambrose, Ph.D., who supervised the graduate students who conducted the study.
In a separate yearlong study of 155 women ages 65-75, UBC researchers also found that weight lifting and walking maintained cognitive function. Those who functioned at a higher level at the start of the clinical trial improved more than those with lower cognitive function, which was not the result the researchers were expecting.
A Japanese study over a year of 47 seniors ages 65 to 93 found that those who exercised for 90 minutes a day improved significantly their ability to use language.
"These latest studies show that resistance training is emerging as particularly valuable for older adults," said William Thies, chief medical and scientific officer for the Alzheimer's Association.
Having trouble walking could be a sign of a decline of cognitive function, concluded "gait analysis" studies reported at the Alzheimer's Association conference.
Seniors walk slower, their pace and the lengths of the steps they take varies more as their cognitive function declines, according to a Swiss study of 1,153 seniors with an average age of 77.
"Those with Alzheimer's dementia walked slower than those with MCI, who in turn walked slower than those who were cognitively healthy," said Stephanie A. Bridenbaugh, M.D., of the Basel Mobility Center, who led the study.
A Dutch study of 1,232 people age 49 and older found that the speed with which seniors process information is associated with the rhythm aspect of gait; executive function is associated with pace and variability, and fine motor speed is associated with how well seniors perform a tandem walk (where the heel of the front foot is placed directly touching the toes of the back foot). These researchers did not find any association between gait and memory.
These studies don't break a lot of new ground, said Carol Schramke, a neuropsychologist with the Neuromuscular Center at Allegheny General Hospital, North Side.
"We've always talked about people who can't walk and chew gum at the same time," Dr. Schramke said.
The gait studies are like the buzz a few years ago that indicated a deterioration in the sense of smell can be a warning sign for Alzheimer's, she said.
Though helpful as indicators, gait studies and smell tests can't replace a comprehensive neuropsychological assessment to diagnose a patient's cognitive status, Dr. Schramke said.
"None of these things are perfect, but they're all pieces of the puzzle," she said.