Aerobic Exercise Increases the Size of the Hippocampus in Seniors

Why is this interesting? To help understand, a little background is necessary. The hippocampus sits deep inside the brain in the medial temporal lobe, and has an important role in long-term and other types of memory formation, including spatial navigation. After middle age the hippocampus starts to shrink, and this has been shown to be associated with loss of memory and an increased risk of dementia. Researchers at the universities of Pittsburgh, Illinois, and Ohio State and rice University wanted to see if aerobic exercise would help seniors counteract age-related hippocampal shrinkage and improve spatial memory. The published the results of their study online in the Proceedings of the National Academy of Sciences.

Volunteers in their mid-60s without dementia were recruited and randomly allocated to one of two groups: one group began an exercise regime walking round a track for 40 min a day, three days a week; the other group did stretching exercises three times a week. All 120 participants had magnetic resonance images at baseline and after six and 12 months. Spatial memory tests were done at the same intervals. Blood was taken for analysis of the brain-derived neurotrophic factor (BDNF), which is known to be involved in learning and memory.

The aerobic exercise group had on average increases in volume of the left and right hippocampus of 2.12% and 1.97%, respectively, at the end of the one-year study. The same regions in the stretching exercises group decreased in volume by 1.40 and 1.43%, respectively. Thus aerobic exercise effectively reversed age-related loss in hippocampal volume by 1 to 2 years. The volumes of other areas of the brain (e.g. the caudate nucleus and thalamus) were unaffected by exercise.

The increased hippocampal volume in the aerobic exercise subjects was associated with raised serum levels of BDNF. However, the study fell short of showing a group affect on memory using the spatial memory test; both groups showed significant improvements, both in accuracy and speed. Although analysis showed that higher aerobic fitness at baseline and at the end of the study was associated with better individual spatial memory scores, there was no significant difference between the average scores of the two groups. The principal researcher suggests this is probably a statistical artifact due to large individual differences within the groups; when subjects with larger hipper campaign were selected, they had better memory performance, both at baseline and at the end of the study.

This study shows that it's possible to overcome the age-related reduction in hippocampal volume with moderate aerobic exercise, and it's likely that this will be associated with improvement in at least one type of memory. Surely this is enough to encourage aerobic exercise for baby boomers as they enter their senior years!