Leg strength is a good indicator of over all health. This fact is the basis for widely used simple health assessment:
Now a study suggests that leg strength may also be a good measure of cognitive aging. From the abstract:
Objectives: We aimed to test whether muscle fitness (measured by leg power) could predict cognitive change in a healthy older population over a 10-year time interval, how this performed alongside other predictors of cognitive ageing, and whether this effect was confounded by factors shared by twins. In addition, we investigated whether differences in leg power were predictive of differences in brain structure and function after 12 years of follow-up in identical twin pairs. Methods: A total of 324 healthy female twins (average age at baseline 55, range 43-73) performed the Cambridge Neuropsychological Test Automated Battery (CANTAB) at two time points 10 years apart. Linear regression modelling was used to assess the relationships between baseline leg power, physical activity and subsequent cognitive change, adjusting comprehensively for baseline covariates (including heart disease, diabetes, blood pressure, fasting blood glucose, lipids, diet, body habitus, smoking and alcohol habits, reading IQ, socioeconomic status and birthweight). A discordant twin approach was used to adjust for factors shared by twins. A subset of monozygotic pairs then underwent magnetic resonance imaging. The relationship between muscle fitness and brain structure and function was assessed using linear regression modelling and paired t tests. Results: A striking protective relationship was found between muscle fitness (leg power) and both 10-year cognitive change [fully adjusted model standardised β-coefficient (Stdβ) = 0.174, p = 0.002] and subsequent total grey matter (Stdβ = 0.362, p = 0.005). These effects were robust in discordant twin analyses, where within-pair difference in physical fitness was also predictive of within-pair difference in lateral ventricle size. There was a weak independent effect of self-reported physical activity. Conclusion: Leg power predicts both cognitive ageing and global brain structure, despite controlling for common genetics and early life environment shared by twins. Interventions targeted to improve leg power in the long term may help reach a universal goal of healthy cognitive ageing.
You can find a popular account here.
Myelination is the process of forming fatty sheaths around neurons, allowing them to transmit messages faster.
Now, a paper in Nature, reports the existence of activity-dependent myelination, a previous unknown form of brain plasticity. Here is the abstract:
“The synapse is the focus of experimental research and theory on the cellular mechanisms of nervous system plasticity and learning, but recent research is expanding the consideration of plasticity into new mechanisms beyond the synapse, notably including the possibility that conduction velocity could be modifiable through changes in myelin to optimize the timing of information transmission through neural circuits. This concept emerges from a confluence of brain imaging that reveals changes in white matter in the human brain during learning, together with cellular studies showing that the process of myelination can be influenced by action potential firing in axons. This Opinion article summarizes the new research on activity-dependent myelination, explores the possible implications of these studies and outlines the potential for new research.”
As I have pointed out before, there is reason to be skeptical of oversimplified versions of the ten thousand hour rule. Talent is a real phenomenon and it does contribute to performance. Having said that, I think we can learn a lot from studying the intense training regimes of high performers. The lessons learned may have broad applicability for education.
At the other extreme is the five hour rule:
(hat tip to BoingBoing)
Nature, perhaps the world’s most prestigious science journal has published “Meta-analysis of the heritability of human traits based on fifty years of twin studies.” Here is the abstract:
“Despite a century of research on complex traits in humans, the relative importance and specific nature of the influences of genes and environment on human traits remain controversial. We report a meta-analysis of twin correlations and reported variance components for 17,804 traits from 2,748 publications including 14,558,903 partly dependent twin pairs, virtually all published twin studies of complex traits. Estimates of heritability cluster strongly within functional domains, and across all traits the reported heritability is 49%. For a majority (69%) of traits, the observed twin correlations are consistent with a simple and parsimonious model where twin resemblance is solely due to additive genetic variation. The data are inconsistent with substantial influences from shared environment or non-additive genetic variation. This study provides the most comprehensive analysis of the causes of individual differences in human traits thus far and will guide future gene-mapping efforts.”
A post by Dr. Greger explores international differences in Alzheimer’s disease:
“The rates of dementia differ greatly around the world, from the lowest rates in Africa, India, and South Asia, to the highest rates in Western Europe and especially North America. Is it all just genetics? Well, the incidence of dementia and Alzheimer’s disease is significantly lower for Africans in Nigeria than for African Americans in Indianapolis, for example—up to five times lower.”
He notes that:
“Alzheimer’s rates of Japanese-Americans living in the U.S. are closer to that of Americans than to Japanese. When people move from their homeland to the United States, Alzheimer’s rates can increase dramatically. Therefore, when Africans or Asians live in the United States and adopt a Western diet, their increase in Alzheimer’s risk suggests that it’s not genetics.”
But read the whole thing.
You can see a map of Alzheimer’s/dementia deaths by country here.
This article in The Atlantic examines why so many writers are also runners:
“Writers, like runners, often like the idea of their pursuit more so than the difficult work. The appeal of a running regimen is how the miles not only condition the body, but free up a space for the creative mind.”
The claim here is, of course, anecdotal. Author Nick Ripatrazone gives us no statistics, we do not really know what percentage of writers are also runners. However, as readers of this blog know, I believe there is evidence for the cognitive benefits of exercise.
I abandoned running some years ago, because of the damage it was doing to my body. I am however, a committed walker on a 10,000 step a day plan. On most days I spend an hour walking on the treadmill, practicing foreign languages (currently Japanese and Hindi) and listening to podcasts.