Physical activities may not protect against underlying markers for Alzheimer's disease

While participating in physical activities such as bike riding, dancing, walking and gardening and mentally stimulating activities such as crosswords and reading may reduce the risk of Alzheimer's disease, they may not do so by affecting the underlying markers for the disease, according to a study published in the June 10, 2015, online issue of Neurology®, the medical journal of the American Academy of Neurology.

"While a lifelong history of physical and mental activity may support better memory and thinking performance, this relationship may possibly be separate from any protection against the markers of Alzheimer's disease in the brain," said study author Keith A. Johnson, MD, with Harvard Medical School and Massachusetts General Hospital in Boston.

The study involved 186 people with an average age of 74 who were free of memory and thinking problems. Participants reported their physical and mental activity levels over their lives as well as current mental activities. They also wore pedometers for seven days to track current physical activity. The participants had PET and MRI scans to measure the amount of amyloid-beta deposits in the brain, which occurs with Alzheimer's disease. The scans also measured the brain's metabolism and whether the hippocampus area of the brain was shrinking, also signs of Alzheimer's. In addition, participants took tests of their thinking and mental abilities.

The study found that participants who took part in stimulating cognitive activities had significantly higher IQ and better cognitive performance compared those who did not take part in mentally stimulating activities very often. There was no relationship between frequent mental or physical activity and any of the markers of Alzheimer's disease in the brain.

"This suggests that sustaining a lifetime of intellectual engagement may help preserve cognitive function into old age," said Johnson. "In addition, our findings should not discourage people from engaging in physically and mentally stimulating activities, as they have been shown in numerous studies to generally offer many brain benefits," said Johnson.

Johnson noted that the study was limited because it did not follow the participants over a long period, but asked them to remember their activities from the past. He said studies that follow people's activities over time are needed to further test the findings.