CHICAGO – An active lifestyle positively influences brain volume in older adults with or without Alzheimer’s disease, a magnetic resonance imaging study revealed.
Among 876 individuals, the average gray matter volume was 663 mL in those with an active lifestyle, compared with 628 mL in those with an inactive lifestyle. That equates to a significant 5% difference (P value less than .05).
“That is a large number difference when you consider the tremendous biologic forces that have to be at work for gray matter volume to decrease,” lead author Dr. Cyrus Raji said in a press briefing at the annual meeting of the Radiological Society of North America.
Prior research has looked at the influence of individual lifestyle factors such as obesity or walking on brain structure, but not a variety of activities, as was done in the current study. Improving lifestyle could reduce the risk for Alzheimer’s disease by 50%, resulting in 1.1 million fewer cases in the United States, said Dr. Raji, a radiology resident at the University of California, Los Angeles.
“In the United States, the lack of physical activity is the No. 1 most powerful lifestyle factor, contributing to 21% of cases of Alzheimer’s disease,” he said. “Worldwide, it is the third most powerful risk factor after low educational attainment and smoking.”
To determine how lifestyle influences brain structure, the investigators used MRI scans and clinical data collected over 20 years from 876 individuals enrolled at four sites in the Cardiovascular Health Study. The Minnesota Leisure Time Physical Activity Questionnaire was used to assess caloric expenditure during 15 different aerobic activities: swimming, hiking, aerobics, jogging, tennis, racquetball, walking, gardening, mowing, raking, golfing, bicycling, dancing, calisthenics, and riding an exercise bike. A technique called voxel-based morphologywas used to quantify the amount of brain matter in the MRI scans.
The participants expended an average of 1,093 kcal/week. Overall, 42% were men, 88% were white, and about 25% had been diagnosed with Alzheimer’s disease or mild cognitive impairment (MCI). The cohort was largely overweight, with an average body mass index of 27 kg/m. Their average age was 78 years.
The analysis controlled for head size; age; gender; body mass index, which has been related to brain structure and atrophy; small vessel ischemic disease, which reflects processes like diabetes and hypertension that can affect the brain; Alzheimer’s or mild cognitive impairment (MCI) status; and study site.
The most active participants burned an average of 3,434 kcal/week, compared with 348 kcal/week in the least active participants.
There was larger bilateral gray matter volume in the cingulate gyrus, hippocampus, and temporal lobes – areas responsible for memory and learning – among individuals who burned the most calories per week, compared with those who burned the fewest, Dr. Raji said.
“That means the areas of the brain that are benefiting the most from this active lifestyle are also the areas affected in Alzheimer’s disease and are also responsible for cognition,” he explained.
The same findings were observed in participants with Alzheimer’s disease or MCI. “People with Alzheimer’s who were more physically active in our study weren’t cured, but they had less deterioration in their brain matter volume, compared with the sedentary individuals,” said Dr. Raji, who described the study as one of the largest voxel-based imaging studies of humans ever done.
Press briefing moderator Dr. Candice A. Johnstone of the Medical College of Wisconsin in Milwaukee said in an interview that what’s unique about the study is that it shows that physical activity actually changes brain volume and that this benefit can be obtained through a variety of activities. This is especially important when counseling patients who may have difficulty walking.
What the study fails to address, however, is whether an active lifestyle will have an impact on the symptoms of Alzheimer’s or MCI. “Whether physical activity can significantly alter the course remains to be seen,” she said. “It may be that people with changes in brain volume may be more likely to have [fewer] symptoms because their brain’s actively working to enhance those areas, but that’s the subject of future research. We do not know that.”
By Patrice Wendling