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Posts Tagged ‘aging’

Exercise only preserves the muscles you actually use

January 19th, 2012

It was great to see the big response to the MRI pics I posted a couple of days ago showing the well-preserved leg muscles of a 70-year-old triathlete. Very striking stuff. But let me now offer the following caveat:

This is a figure from a new study from the University of Western Ontario, just posted at Medicine & Science in Sports & Exercise. They analyzed the biceps brachii (arm muscles) of nine young runners (average age 27), nine old non-runners (70), and nine lifelong masters runners (67). They measured the number of functional motor units (i.e. group of muscle fibres activated by a single motor neuron), which typically declines with age. As you can see, the two old groups were pretty much the same, far below the young group.

In contrast, the same researchers studied leg muscles (tibialis anterior) in a similar group of volunteers last year (as I blogged about here) — in that case, the older runners did preserve the number of motor units. What this tells us is that exercise, on its own, doesn’t preserve all the muscles in your body: in the words of the researchers, there’s no “whole body neuroprotective effect,” or at least none that shows up in this relatively small study. It just preserves the muscles you’re using on a regular basis. So that’s still good news for triathletes, but maybe not as good for runners and cyclists!

The incredible unaging triathlete

January 14th, 2012

Here’s a pretty graphic illustration, from a recent paper by Dr. Vonda Wright and her colleagues (hat tip to Laura McIntyre for the forward), of the importance of lifelong physical activity:

It’s from a new study freely available at The Physician and Sportsmedicine that took detailed measurements of 40 masters athletes between the ages of 40 and 81, and found a surprising lack of age-related muscle loss:

This study contradicts the common observation that muscle mass and strength decline as a function of aging alone. Instead, these declines may signal the effect of chronic disuse rather than muscle aging.

 

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Exercise -> serotonin -> antidepressant

November 14th, 2011

It’s well-established that exercise can be a powerful tool against depression (as Gretchen Reynolds wrote about in the New York Times a few months ago). What’s less clear is how and why it might help. A new study in  Medicine & Science in Sports & Exercise, from researchers at the University of Sherbrooke, offers some evidence for the theory that exercise can boost serotonin levels in the brain. This, of course, is pretty much the same as what the most common antidepressants (SSRIs: selective serotonin reuptake inhibitors) do.

The study was pretty straightforward. They had 19 men with an average age of 64 perform a 60-minute bout of exercise at moderate intensity (average HR 129 beats per minute, 68% VO2max). Then they measured several proxies of serotonin production, since it’s very difficult to directly measure neurotransmitters in the brain. The result: levels of tryptophan — the key precursor which is converted into serotonin — roughly doubled.

Is this a surprise? There was previous evidence in studies of rodents and younger humans that exercise boosted tryptophan availability, but it wasn’t clear whether the same effect would occur in older adults. This is particularly important because we become increasingly susceptible to depression as we age, suggesting that some of the mechanisms that help us ward off depression stop working quite as well.

Of course, one of the problems with “prescribing” exercise as a depression treatment (as Reynolds notes) is that once you’re depressed, it can be extremely difficult to summon the motivation needed to maintain a regular exercise program. Still, this study suggests that exercise might help to prevent depression in the first place, particularly as you get older.

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Aging: does the average decline as much as the extremes?

October 24th, 2011

My Jockology column in today’s Globe and Mail takes another look at aging and physical decline:

It’s the chicken-and-egg question of aging: Do we become less active as we get older because our bodies start to break down, or do our bodies start to break down because we allow ourselves to become less active?

For years, it was widely accepted that humans would start getting slower, weaker and more fragile starting in their 30s. But new studies on topics ranging from the cellular mechanisms of aging to the time-defying performances of masters athletes are forcing researchers to question this orthodoxy. It seems increasingly likely that the first signs of decline are more a function of lifestyle than DNA: If you keep using it, you’ll be well into middle age before you start losing it. [READ THE WHOLE ARTICLE...]

One of the studies discussed in the article is this analysis of the finishing times of 900,000 German marathoners and half-marathoners, published last year. The researchers argue that the rate of decline of mid-packers is a better way of judging “natural” aging processes compared to the outliers who set age-group world records. For fun, I plotted the average finishing times of the runners in the German study, and superimposed the curve that you’d get if they declined at the same rate as age-group records. It’s pretty clear that this group of midpackers does decline at a slower rate:

 

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Knee bends make you smarter?

October 5th, 2011

The best way to improve your cognitive function is to… strengthen your quadriceps muscles?! That (sort of) is the message of a new study in the European Journal of Applied Physiology by researchers in Japan.

In brief: they measured cognitive function in a group of 39 older men (average age 69) using the “Mini-Mental State Exam” (MMSE), and compared to results to measures of elbow, knee and ankle strength. They found that knee extensor strength (i.e. quadriceps) was significantly correlated with MMSE scores, but elbow and ankle strength weren’t. To some extent, this isn’t surprising: cognitive decline is often linked to declining ability to carry out everyday tasks, though it’s not entirely clear which is the cause and which is the effect. (Does physical weakness condemn you to sit helplessly in your chair, causing your mental faculties to atrophy? Or is it mental decline that stops you from doing your usual activities, causing your muscles to weaken?)

But this doesn’t explain why knee strength predicted cognitive function while elbow and ankle strength didn’t. One possibility is that the knee is more significant because it’s a larger muscle mass, so it’s more capable of affecting the levels of hormones like insulin-like growth factor 1 circulating in your body, which in turn affect brain health. This is pretty speculative. A simpler possibility is that knee strength is more important to mobility (e.g. getting in and out of chairs) than ankles or elbows. (And a third possibility is that the result is simply a fluke due to small sample size.)

Anyway, this raises the question: can you get smarter by doing deep knee bends? The study tried this, putting 27 of the subjects through a three-month, six-day-a-week home training program involving simple things like sitting in a chair then standing up. The results were a little unclear because the changes were very small after such a light training program — but the increases in MMSE score were indeed correlated (with p<0.05) with increases in knee extensor strength. In other words, those who achieved the biggest gains in knee strength also saw the biggest gains in MMSE score.

So what does this mean? I don’t think it’s anything earth-shatteringly new. To keep your wits about you, you have to stay active; to stay active, you need to have the physical ability to get around. Most previous studies on exercise and cognition have focused on aerobic exercise, which produces very strong effects on the brain. The message here is that you can’t neglect your muscles — particularly the big ones that get you out of your chair and walk you down the street.

The incredible shrinking hippocampus (and how to stop it)

September 27th, 2011

Over the last few years, a bunch of studies have built the case that aerobic exercise does something to keep your brain in good working order as you age — or perhaps more accurately, it does several good things for your brain. Last week, I blogged about a study showing that exercise stimulates the growth of new mitochondria in the brain. In the comments of that post, Seth Leon pointed out another new study — this one in the September issue of Neuropsychology — that links exercise to greater volume of the hippocampus, which in turn improves memory.

I’ve been particularly interested in the hippocampus ever since I wrote this article in The Walrus back in 2009, looking at suggestions that increased use of GPS navigation would lead to decreased volume of the hippocampus, where our direction-finding skills reside. And smaller hippocampi are associated with increased risk of age-related cognitive impairment. One of the researchers I spoke to worried that this is part of larger shift:

But Bohbot sees the decline in spatial thinking as part of a broader shift toward stimulus-response, reward-linked behaviour. The demand for instant gratification, for efficiency at all costs and productivity as the only measure of value — these sound like the laments of the nostalgist in the Age of the Caudate Nucleus. But here, they’re based on neuroscience. “Society is geared in many ways toward shrinking the hippocampus,” she says. “In the next twenty years, I think we’re going to see dementia occurring earlier and earlier.”

I can’t count the number of times I’ve taken wrong turns since writing that article because of my stubborn refusal to use GPS unless absolutely necessary! But I digress…

Anyway, this new study, by researchers at the University of Illinois, looked at a group of 158 sedentary adults between 60 and 80 years old, to look for evidence for the following model:

The basic gist is straightforward: they hypothesize that fitness (as measured by a graded exercise test to exhaustion) predicts hippocampus size, which in turn predicts working memory, which in turn predicts how frequently you forget things. What’s new about this study is that they separately consider age, BMI, sex, physical activity, and education to see if any of them are skewing the results. Here’s what they find:

By and large, the data supports their hypothesis. There are a few wrinkles: for example, age, in addition to affecting fitness, also has a direct effect on hippocampus size. That means no matter how fit you are, your hippocampus is still getting smaller. Also, physical activity (that’s the PASE box) didn’t directly contribute to fitness — but that’s not surprising, because the volunteers had to be sedentary in order to be admitted to the study, so they all had roughly the same (lack of) physical activity.

Bottom line: aerobic fitness is good for the brain — and in particular, it’s good for the hippocampus. So maybe if I get enough exercise, I’ll start letting myself use that GPS navigation system.

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The philosophy of ignoring health journalism

August 11th, 2011

There’s an interesting opinion piece in the New York Times by Notre Dame philosopher Gary Gutting that starts out asking some questions that I find interesting, and then answers them in a way I find ridiculous. The problem statement:

Almost every day I read about a new medical study that says I would be healthier if, for example, I ate more fish, drank red rather than white wine, took enchinacea [sic], or began practicing yoga.   Do such studies represent a significant body of knowledge that I should pay attention to?

Good question, and particularly of interest given that this blog (and a large part of my professional journalistic output) is devoted to parsing and disseminating such studies. Gutting goes on to discuss the difference between observational studies and prospective trials — correlation and causation — and laments that the media chooses to cover so many observational findings. This is a problem, he suggests, because keeping up on the details of all these studies is so time-consuming, and the results are “subject to constant reevaluation as new results come in.” So what’s the solution?

Taking a broader view, it would seem preferable to keep healthy by a method that is simple, reliable and doesn’t require constant revision and fine-tuning.  We do, after all, have such a method available: simply follow the humdrum standard advice we’ve heard all our lives about eating sensibly, exercising regularly, and having recommended medical tests and exams. Doing this and foregoing the endless calibration of our behavior to the latest research results will be far less stressful, make it more likely that we’ll stick to the method, and allow more time for fulfilling pursuits.  From this point of view, the media’s constant updates on the latest observational studies are counterproductive.

Now, I’m certainly not going to argue against “eating sensibly, exercising regularly, and having recommended medical tests and exams.” That’s great advice. But where does he think that advice comes from? Does the great body of ancestral knowledge passed down from our caveman forebears include any guidance on when to start getting prostate exams, or what the pros and cons of regular mammography are? And what is eating “sensibly” — is that eating like people did 50 years ago? 100 ? 10,000? In Europe? Asia? Africa?

The “common sense” behaviours that Gutting suggests following (as opposed to following “the media’s constant updates on the latest observational studies”) aren’t some sort of innate knowledge that we’re all born with. Those behaviours are learned, and constantly evolving as society absorbs and assesses the studies he’s counselling us to ignore. What his argument really boils down to is a recommendation that we should defer to authority — let the experts decide what constitutes “sensible” living, and just do it. Don’t worry about what the studies say, because if they’re convincing enough, the results will eventually find their way into the canonical set of public health recommendations.

This is perfectly reasonable. I know plenty of people who aren’t interested in the gory details of how their bodies work: they just want to be told what to do, and they want the advice to be simple, easy to implement, and relatively unchanging. Fair enough. But there are also many people who are interested in peeking behind the curtains of the public-health-recommendation sausage factory and evaluating the evidence for themselves. If a new study suggests that previous recommendations about, say, salt recommendations are shakier (yes, that’s a pun) than previously thought, they want to know about it and evaluate its significance themselves.

Of course, there’s plenty of terrible health reporting out there. But even good health reporting is often complex and reports on studies than seem to contradict each other. It has to be that way, because health research is complex and often contradictory. We’re complicated animals in a complicated world. If you want a simple, reassuring message that promises to answer all your questions and solve all your problems, your best bet is probably late-night infomercials.

Anyway, back to Gutting. His final message is that it’s simply not worth the hassle of worrying about all the factors that may or may not improve health and prolong life:

We are all going to die sometime, from something.  Even if I find just the right blend of exercise, diet and herbs that saves me from a heart attack at 60, I may have merely ensured that I will die of cancer at 70.

And really, there’s not much I can argue with here. If dying at 60 and dying at 70 are entirely interchangeable to him, then he’s perfectly right not to waste his time worrying about health. But if you ascribe some value to an extra decade of life (or a greater probability thereof), then you might reach a different conclusion.

What it takes to live to 95

August 9th, 2011

I’m a big fan of studies (like this one from a few months ago) that paint exercise as a fountain of youth that will stave off aging. I’m less fond of studies like the one just published in the Journal of the American Geriatrics Society, from the Albert Einstein College of Medicine, that suggest that longevity is in your genes, and nothing you do makes much difference (abstract here, press release here). But what you can you do? Data is what is (or “are what they are,” if you prefer — Audrey!).

The study: researchers interviewed 477 people between the ages of 95 and 112 to find out about their lifestyles way back when they were 70 (which was considered loosely representative of their adult habits): weight, alcohol consumption, smoking, exercise, whether they ate a low-calorie, low-fat or low-salt diet, etc. This data was compared to similar data collected back in the 1970s from several thousand people born around the same time, representing the general population. The punchline:

Overall, people with exceptional longevity did not have healthier habits than the comparison group in terms of BMI, smoking, physical activity, or diet.

Doh! On the other hand, the same research group has found distinct genetic patterns among people who live to be 100, such as one that gives them abnormally high levels of “good” cholesterol. So does this mean our longevity is written in our DNA and we might as well not worry about silly things like exercise and nutrition?

Well, there was one statistically significant difference between the super-agers and the general population: obesity. Being overweight (BMI 25-30) didn’t seem to make a difference, but fewer of the old folks were obese (BMI over 30): 4.5% versus 12.1% in the men, and 9.6% versus 16.% in the women. Still that’s a relatively minor difference.

The more important thing to remember is that this is a study of extreme outliers. So, if the results hold up and are confirmed by other studies, it may tell us that all the broccoli and chin-ups in the world won’t make you live to 100. You need the genes to make it that far. But if you don’t have the genes, then you do need the lifestyle factors to make it as far as possible — after all, there’s no question that factors like exercise and not smoking are linked to longer lifespans. They may not get you to 100, but there’s still a big difference between, say, 65 and 85!

A universal law of decline for running, swimming… and chess?!

July 10th, 2011

Which do you lose first as you get older: speed or endurance? Swimming speed or running speed? Athletic ability or cognitive ability? There have been dozens of studies investigating these questions, often with conflicting results. But all these processes of decline follow the same basic mathematical rules, according new study in the journal Age by researchers in France (press release here; full text freely available here).

The abilities of all living things follow a basic pattern: (1) you start at zero when you’re born; (2) as you get bigger, stronger and more experienced, your abilities increase exponentially; (3) as your body starts to age and wear out, an exponential decline kicks in; (4) you end up back at zero when you die. During your peak years, the balance between the rising and falling exponential curves gives you a brief plateau.

Now, this seems like a fairly bland set of statements. After all, they’re not taking into account loss of muscle mass with aging, and shortening of telomeres, and loss of tendon elasticity and so on. They’re just wrapping all the details into a general curve. And in fact, their argument is even bigger than that: this curve doesn’t just describe your 100-metre dash time. It describes the life of cycle of individual cells; of human beings; and of species in general. They claim.

To explore this theory, the researchers studied the career trajectory of more than 11,200 individual track athletes, swimmers and chess players. Here’s some sample data: track is at the top (Ato Boldon, 100m, blue; Sandie Richards, 400m, red), swimming is middle (Peter van den Hoogenband, 100m free, blue; Martina Marcova; 200m free; black), and chess is the bottom (Jonathan Simon Speelman in blue, Jan Timman in black).

Convinced? Yeah, me neither, to be honest. But statistically, they claim that this model accounts for 91.7% of the variance at the individual level, and 98.5% at the species level. For “species level,” they looked at age-class bests. The data below shows curves for (top) men’s 100m free, women’s 200m free and women’s 400m run; (middle) best chess performance by age; (bottom) men’s marathon. The marathon graph is the most interesting, because it shows the two exponentials — rising and falling — that are added together to produce the model.

So what does this all mean? I’ve got to be honest: I found the paper pretty hard to understand. (Fortunately, the full text is freely available online, so you don’t have to rely on my attempts to decipher it!) I don’t think we’re supposed to look at those graphs and assume that Ato Boldon is going to be either dead or paralyzed when he turns 64. Rather, I think this model is intended to help us understand what the future evolution of sport (and other human capabilities) as a whole might be. As the researchers conclude:

The study of the world records progression and top performances revealed a plateau in a majority of studied events. We extended the studied data and the model to a broader context: the development of physiological performance in the process of ageing. This questions the upcoming evolution of the biphasic pattern presented here: will the phenotypic expansion continue, plateau or decrease? Do we have the ability to maintain our development in a sustainable way?

Good questions — but of course, they don’t know the answers. Let’s see what Usain Bolt does this year and next, then we’ll talk.

[BONUS: Here's a link to the appendix where they list the fitting parameters for the 11,200 careers they analyzed. Interesting tidbit: the average ages of peak performance for different events. E.g. for running: 23.3 for men's 10,000m, 31.6 for men's marathon. That's a big gap!]

Vigorous exercise prevents “silent strokes” in older adults

June 10th, 2011

Just noticed a press release about a study on exercise and brains in older people, reaffirming the well-established idea that there are benefits to more vigorous exercise that you can’t get from mild exercise:

Older people who regularly exercise at a moderate to intense level may be less likely to develop the small brain lesions, sometimes referred to as “silent strokes,” that are the first sign of cerebrovascular disease…”These ‘silent strokes’ are more significant than the name implies, because they have been associated with an increased risk of falls and impaired mobility, memory problems and even dementia, as well as stroke,” said study author Joshua Z. Willey, MD, MS, of Columbia University…

The study involved 1,238 people who had never had a stroke. Participants completed a questionnaire about how often and how intensely they exercised at the beginning of the study and then had MRI scans of their brains an average of six years later, when they were an average of 70 years old.

You can read the press release for more details, but the basic gist is: these lesions are not uncommon (16 percent of participants had them), and those who did moderate to intense exercise were 40 percent less likely to have them than those who did light exercise or no exercise, while controlling for other risk factors like blood pressure, cholesterol and smoking. Just another data point to bear in mind!