In December, one of my blogs focused on research linking walking with relatively protection from dementia in later life. As I pointed out in the blog, so-called ‘epidemiological’ studies of this nature are good for discerning associations between things, but can’t be used to determine that one thing is actually causing another. In other words, walking may be associated with a reduced risk of dementia, but that does not mean that walking protect against dementia.
To demonstrate ‘causality’, what we generally need is ‘intervention’ studies. Essentially, these are studies where individuals are randomly assigned to the treatment or strategy being tested, or a ‘placebo’ (supposedly inactive) treatment. This week saw the publication of an intervention study which assessed the effect of exercise on the structure and function of the brain in older adults over the period of a year .
In this study, half of the study subjects took aerobic exercise in the form of three, 40-minute walks each week. The others engaged in ‘stretching and toning’ activity.
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 hippocampus (the control group saw a small reduction in volume of this brain structure).
- Higher levels of brain derived neurotropic factor.
- Improved memory.
This study provides good evidence that exercise can lead to improved brain function (and is not just linked with it). What is more, this study shows that even quite low-intensity activity of relatively short duration can have benefit here.
1. Erickson KI, et al. Exercise training increases size of hippocampus and improves memory. PNAS 31 January 2011 [epub ahead of print]