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 [1].
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.
References:
1. Erickson KI, et al. Exercise training increases size of hippocampus and improves memory. PNAS 31 January 2011 [epub ahead of print]
It isn’t walking weather for my age group so instead I lie on my back on my bed and throw my legs into the air above my head and sort of peddle. I do this for about three-quarters of an hour with very short breaks when I get short of breath. Would this be considered an exercise to improve the structure and function of my brain.
I have been going to a warm pool for about a year now as I cannot walk for long distances with my legs I simply ride my little suspension device up and down the pool for about 30 minutes three times a week
Could this be of benifit the same as walking
My BP is within normal limits now
Hi Audrey. What age group are you? I’ll be 56 in March. If you’re getting out of breath from your exercise, it’s doing you good. Or is the position that you’re lying in compressing your diaphragm and making it harder for you to breathe?
I go for a walk after every meal, whatever the weather. I have a treat when I get back so that I have something to look forward to while I’m walking. I don’t care about the calories in my treat. I’m walking to improve the insulin sensitivity of my muscles, not lose weight (although I am losing weight and I am getting slimmer).
Nigel Kinbrum: Lucky old you. I have been on an almost totally protein diet for three months and haven’t lost an ounce. I shall be 81 at the end of March and used to walk everywhere, play tennis, swim and dance all night.
Something has to give, dammit. Your point about compressing my diaphragm is well taken – I made a point of looking out for it but am pleased to tell you I am breathless from exercise.
Thank you for pointing out that association is not causation. Unfortunately, it seems a common mistake, perhaps even repeated in this article.
To jump from “walking improves something” to “walking causes something” is to make the same error.
For example, walking may cause deep breathing. Deep breathing will press on a vein behind the breast bone, pushing lymph fluid into the circulatory system.
To test which, walking or deep breathing “causes” the improvement, one group should do deep breathing but no other exercise while the other group walks.
Deep breathing also oxygenates the blood.
Then there are secondary effects. It has been shown that those who sit for extended periods of time do worse than those who get up for a brief period and sit back down. If walking takes time away from extended sitting, it may be that just getting up provides much of the benefit.
What I am trying to point out, is that correlation is not causation, and that causation may often be multiple interrelated factors. Or even some accidental co-factor, to be discovered later.
Ted
ps: does walking to and from the pub count?