A study shows that one year of aerobic exercise can improve memory function in patients with amnestic mild cognitive impairment (MCI), who experience memory loss and are at high risk for Alzheimer’s disease.

In the US, 11% of the population over the age of 65 has Alzheimer’s disease, and there are about 5.4 million people living with Alzheimer's-related memory impairment. About 10% per year of those with mild cognitive impairment progress to Alzheimer’s disease.

Aerobic exercise is known to improve cardiorespiratory and cognitive function in older adults with and without MCI, although the mechanisms of cognitive improvement are not understood.

This study suggested that aerobic exercise improves brain vascular function, leading to brain function improvement. Specifically, researchers suggest that memory improvement is due to increased blood flow to the Anterior Cingulate Cortex (ACC) area of the brain, which increases with aerobic exercise.

The study used Magnetic Resonance Imaging (MRI) to measure resting cerebral blood flow (CBF) in 30 patients with amnestic MCI.

Half of the participants were assigned to perform aerobic exercise, and the others to perform non-aerobic stretching. Both groups were age, gender, education and Body Mass Index matched. They underwent training for one year.

The aerobic exercise group was trained to maintain their heart rate (HR) within 55-65% of max HR during exercise. The stretch group performed upper and lower body stretching and maintained their HR below 55% of max HR.

Both groups began training at 30 minutes per session, 3 sessions per week. Exercise frequency and duration were gradually increased to 4-5 sessions per week at 40-50 minutes per session over a period of 6 months, and maintained at that level for another 6 months.

Memory function was assessed using a standard paragraph recall task, and resting CBF was measured at the start and end of training using arterial spin labeling (ASL) MRI.

After one year of training, cardiorespiratory fitness was significantly improved in the exercise group, while there was no change for the stretch group.

Similarly, memory performance improved significantly in the aerobic exercise group, while the stretch group did not show improvement.

Pre and post training CBF increases were shown in the brain regions ACC, the medial frontal gyrus (MFG), and the inferior frontal gyrus in the aerobic group.

The ACC and MFG represent a critical node in working memory, involved in monitoring of memory and allocation of attention supporting memory.

Increase in CBF in the ACC shown in this study is in line with findings of previous studies, which demonstrated aerobic exercise induced CBF increase in the ACC brain region in cognitively normal older adults.