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Understanding Twins
Listen Up, Women! Super Strong Legs Make Super Strong Brains
Is this just headline hype or is it the real deal?
Posted January 23, 2016
Walking up the fifty or so steep steps to the top of our garden this morning made the muscles in the backs of my legs ache briefly. Not good, I thought, having recently read the waterfall of reports on a recent study published by Dr. Claire Steves and her colleagues at Kings College, London. Her group have been studying twins for many years, and they recently published an article in Gerontology ("Kicking Back Cognitive Ageing: Leg Power Predicts Cognitive Ageing after Ten Years in Older Female Twins") that has been reported numerous times in the UK press, including the Guardian and the UK Huffington Post.
The researchers assessed 324 healthy women twins (with a mean age of 55 at the start of the study) on two occasions; at the beginning and end of a ten year period. Cognitive abilities including learning, memory, and problem solving were assessed using a large computerized battery of tests. In addition they measured many physical attributes, including leg power, at the beginning and end of the study. MRI brain scans were also carried out at the close of the study so they could see if twins who had better physical strength and/or less cognitive deterioration over the ten years had less loss of brain gray matter (the layer of neurons that make up the cortex).
The take-home message that their results suggest is this: In older healthy women, greater leg explosive power (LEP—‘as if performing an emergency stop in a car’) is significantly correlated with less age related cognitive decline, and this is reflected by MRI measures of the brain’s gray matter at the end of the study. Of course the reports in the press and on TV simpify this complex study enormously, and if you read these popular reports you might think that the study was carried out on 324 identical twins. That would have been very newsworthy as identical twins have the same genetic makeup and thus any differences with respect to cognitive decline and brain structure between the twins in each pair would indicate that it was due to non-genetic, environmental factors. But if you read the original article it is clear that only 127 of the twins were identical (monozygotic, MZ) and 197 were non-identical (dizygotic, DZ). The MRI brain scans were carried out on a small subsample of this larger group, just 20 pairs of twins, including both MZ and DZ . It is always wise to go to the source of reports in the popular press before you embark on a programme of lifestyle changes.
In this case, while the popular press headlines and reports of this study are designed to make the reader think they are more dramatic and conclusive than they are, and you’d better get out there and start exercises to strengthen your legs, in this case this doesn’t matter too much because the original study has a very well described methodology, elegant and appropriate statistics, and has been published in a respected peer review journal. In the scientific article the researchers do not claim that they have found the golden egg, but more modestly that (i) they have produced results that support other studies where physical activity is related to better cognitive function in older people, and (ii) that much more research is needed to discover why lower limb power might be the best measure of physical activity in this type of study where correlations with cognitive decline over time are looked at. This is exactly how science is meant to work; hypotheses are tested, findings are published, new studies are designed to replicate or extend the previous studies, and on it goes.
I previously posted a blog on this site that suggested that dancing was good for the brain ('Dance so there is a Tomorrow,' February, 2013). Other studies suggest Suduko is great, and on it goes. Reading Psychology Today articles and more importantly thinking about them is almost certainly another activity that will add to your chances of hanging on to your cognitive capabilities as you age, and even perhaps keeping more of those neurons in action for longer. Personally I’m assuming that writing articles and books (especially novels as they get the creative bits of the mind firing!) will assist me into a good old age. Likewise, the more physical activity we do, the better, and I am betting in a totally non-scientific way that being active in body and mind for as long as possible will never be proven to be a bad thing for our brains. Of course physical activity that involves utilizing slack muscle groups and puts strain on tendons you didn’t know you had must be planned and worked towards gradually; the plethora of sports injuries even in elite sports people demonstrate how easy it is to damage our body. Not so, I think, for mental activity. To my knowedge there is no research that suggests that you can damage your brain by pushing your thinking to new heights. The “tired” brain you feel at the end of eight hours of straining over a difficult essay is more likely to be a tired body: a headache from frowning, tense muscles from sitting too long without moving, a need for more food and sleep which both body and brain require. But you probably won’t be at risk of “straining” your gray matter or your memory-loving hippocampus by too much mental concentration on a very challenging and new task. It is often said that the brain is like a muscle in that we must “use it or lose it,” but the brain is not a muscle and it cannot be strained (although I stand to be corrected when research proves otherwise). The flavor of that quip is fine though; indeed we would be wise to use our brain if we don’t want our cognitive abiities to deteriorate too much, too fast.
Keeping up the motivation to continually challenge your cognitive capabilities can be as difficult as keeping up those physical exercises when what you really want to do is plop down in front of the TV and watch another episode of the same comfortable series you watch every week (and within moderation there is nothing wrong with a bit of plopping out). But the best way to keep up those more challenging and health-giving physical and cognitive activities is to enjoy them, so the more pleasurable ways you can come up with to keep active and keep thinking, the better. That’s why so many people love research that tells us dancing is good for body and brain! Encourage your kids too, whether it is dancing or cycling, cross-words or writing. Another wise saying that research probably supports: It’s never too early or too late to start.
And then of course there is the food we eat and what that does to our body and cognitive abilities… That’s a whole other story with even more popular press hype and real science to get our heads around. At least reading the real science about diet will get you thinking, and we know that that has to be good!
