‘Mild cognitive impairment’ describes a state characterised by impair brain function that is not severe enough to be classified as dementia. Memory issues are a common feature of mild cognitive impairment. It is believed that much of memory function is the domain ofpart of the brain known as the hippocampus (there are two of these, one on each side of the brain).

A study published this week found that a 6-month programme of aerobic exercise (two, hour-long walks each week) in women aged 70-80 with mild cognitive impairment led toenlargement of the hippocampi [1]. Resistance training did not have this effect. Unfortunately, there was evidence that this did not necessarily translate into improved brain performance. In fact, enlargement of the size of the hippocampal size was found to be associated with worse performance on some measures of memory and learning.

However, this is one study, and it’s worth putting it in the context of other research. In a previous study, older adults took three, 40-minute walks each week. Others engaged in ‘stretching and toning’ activities [2]. All study subjects were assessed in a range of ways including memory, levels of ‘brain derived neurotropic factor’ (a substance that stimulates new brain cell development and brain cell communication), as well as the size of a part of the brain known as the hippocampus (which is involved in memory function). Compared to the ‘control’ group, those who engaged in regular walking experienced an increase in volume of the hippocampi, but also saw improvements in memory function. Levels ofbrain derived neurotropic factor rose, too.

In yet another study, a group of sedentary individuals aged 59 – 80 had their brain function assessed [3]. As with the previous study, individuals engaged in either walking (40 minutes, three times a week) or stretching and toning exercises. Study subjects were reassessed after 6 and 12 months.

Assessment took more than one form. One test employed was ‘functional magnetic resonance imaging’ (fMRI). This tests brain activity. One part of the brain the researchers were particularly interested in is known as the ‘default mode network’. This part of the brain in most active when individuals are inwardly focused, but becomes naturally more quiet once someone has to focus on their external environment for some reason.

At the end of the study (12 months), compared to those who had been stretching and toning, those on the walking regime saw, on average, an increase in the default mode network connectivity. They also saw increased activity in another part of the brain (known as the ‘fronto-executive network’) which assists individuals perform complex tasks.

Crucially, though, the walkers did on a range of cognitive tests too, especially those that are sometimes referred to as ‘executive control tasks’ (e.g. planning, scheduling, dealing with ambiguity and multi-tasking). It is these skills, by the way, that do tend to suffer when we age.

As a whole, the evidence suggests the regular walking is good for brain function in adults. Some of the benefits may come from the activity itself. However, I wonder whether at least some of the effect is as a result of factors related to the activity (such as being in natural sunlight).

Whatever the precise mechanism, I think getting out for walks (for those who are able) represents a very doable and sustainable activity that stands to enhance mental functioning and quality of life. No special equipment required. And it’s free, too.

References:

1. ten Brinke LF, et al. Aerobic exercise increases hippocampal volume in older women with probable mild cognitive impairment: a 6-month randomised controlled trial. British Journal of Sports Medicine, 2014; DOI: 10.1136/bjsports-2013-093184

2. Erickson KI, et al. Exercise training increases size of hippocampus and improves memory. Proc Natl Acad Sci USA. 2011;108(7):3017-22

3. Voss MW, et al. Plasticity of brain networks in a randomized intervention trial of exercise training in older adults. Frontier in Aging Neuroscience doi: 10.3389/fnagi.2010.00032