Armed with exercise in the fight against dementia

People are always asking what they can do to protect themselves against Alzheimer’s disease and related dementias.  Concern over the risk of these ailments is evident in the tremendous success of super foods, super supplements, and mind games, all claiming to preserve mental acuity into old age.  Persuasive findings from several recent studies add to a growing body of literature suggesting that physical activity may be especially effective in the fight against dementia.

Brain imaging from a new study in Neurology revealed that seniors who are physically active have less atrophy (shrinkage) than their more sedentary peers. The integrity of their white matter was also superior, meaning that the “wiring” that connects brain regions was healthier.  These folks were in their 70s, so the grueling activities associated with these benefits were things like walking several times a week.  Interestingly, none of these same benefits were seen with mental exercises. While there may certainly be benefit to some of the mind games currently flooding the market, the promising advertising claims appear way ahead of the scientific evidence.

Just days ago, the journal Stroke published evidence that a physically active lifestyle significantly reduces the risk for cognitive impairments and vascular dementia. Vascular dementia is caused by reduced or obstructed blood flow in the brain, and limits the oxygen and nutrients reaching brain cells.  Depending on where blood flow is reduced, symptoms may include confusion, disorientation, and problems with memory or attention.  The relationship between physical activity and reduced dementia risk in this study was robust, even after accounting for education level, age, and other risk factors for dementia.

The strength of these two studies lies in their numbers (both had over 600 participants), but they are limited in that they can only demonstrate associations.  It could simply be that people with healthier brains are more likely to remain active, rather than that activity causes these benefits to the brain. Herein lies the power of intervention studies.

In a 2011 study, Erickson et al. recruited 120 older adults and randomly assigned half of them to a stretching and toning program and half to an aerobic exercise program that consisted of moderate-intensity walking of up to 40 min. at a time.  Six and 12-month follow-ups showed that aerobic exercise physically increased the size of the hippocampus.  This region shrinks in late adulthood, even in those without dementia.  This volume loss impairs memory and increases the likelihood of developing dementia. The people in this study who walked effectively reversed the age-related loss of hippocampal volume by 1 to 2 years.

I think the most powerful message here is that it is never too late.  Some of these participants started walking in their late 70s and early 80s, and their brains physically changed as a result of moving their bodies.  Never mind the reduced cholesterol and blood pressure that undoubtedly came with this exercise…regions of their brain actually grew because they were walking!  Now, there is always a need for more large-scale, controlled interventions, but the science is consistently exposing exercise as a neuroprotective factor—helping to defend against deterioration in the brain.

People are always asking what they can do to protect themselves against Alzheimer’s disease and related dementias.  It seems to me that at least one answer is pretty clear.

Exercise: free Ritalin with no side effects

A lucrative black market now exists for the unprescribed use of stimulant drugs. It’s been in the news quite a bit lately, so I figured it an apt launching point for this blog. It appears the practice of taking ADHD medicines as “study aids” has infiltrated undergraduate student bodies and is trickling down to high schools. Some physicians have even gone so far as to prescribe these medicines “off-label” (meaning for those without any attentional disorders) to low-income children who are struggling to keep up with their peers in school. This appeared in a recent New York Times article, and the Colbert Report did a pretty great satire on the sheer lunacy of what he terms “meducation.”

I don’t want to get too caught up in the ethics or politics of this trend (I’m aware of several students and at least one friend who “supplement” with stimulants), but suffice it to say that I think it’s a slippery and dangerous slope. These drugs stimulate our central nervous systems and can have rather unpredictable effects on neurotransmitters. Some have to be placed on sleep medicines to counteract the medicine’s effects at night, and others grow depressed. There’s a reason these drugs are not available over the counter.

The thing is, who doesn’t want to be more focused and efficient with their time? What student wouldn’t love to be able to party all week and effortlessly pull off an all-nighter before acing an exam? (I’m not implying that works!) We are all busy people who’d jump at the chance to get just a little bit more done in a little less time….to be able to absorb a little bit more of what we read, to be a little more alert during that unending conference, to concentrate a little bit better on writing that report. Here’s where exercise comes in.

The feeling that you are simply a bit more “on” after a workout isn’t just in your head. errr, bad pun. Actually, that’s exactly where it is—in your head. There are very real changes that occur in response to a single bout of exercise. In this context, most people will immediately think of endorphins. Endorphins (from endogenous + morphine) are certainly released with exercise, but they have a greater impact on mood, pleasure, and pain than your ability to focus or concentrate. so, for another post!

It turns out that the systems targeted by ADD/ADHD drugs are the very same ones naturally affected by a single bout of exercise. The psychostimulants used to treat attentional disorders typically work by increasing the availability of certain neurotransmitters, most notably dopamine and norepinephrine. Likewise, a single burst of physical activity elevates the brain’s dopamine, norepinephrine, and serotonin levels. These chemicals all have an impact on our focus and attention. They serve to increase alertness and reduce our urges to seek out new mental stimulations (like that incessant pull to check Facebook just one more time). Exercise also releases epinephrine, which helps mobilize glucose (the brain’s sole source of energy), and may further enhance the availability of the neurotransmitters just mentioned.

The research (both in kids and adults) confirms these benefits of exercise on our mental performance. After exercise, subjects are able to respond more quickly and accurately to cognitive tests that challenge attention and inhibitory control. In “real life,” these lab tasks could translate to being able to tune out distractions at work or home and concentrating on getting the task at hand out of your hands. Studies that have actually measured electrical activity at the surface of the brain (using EEG) have found, again and again, that a single bout of exercise boosts markers of attentional processes. These EEG markers essentially show that more cortical resources are allocated to a given task after exercise than before, and that they’re allocated more quickly. Researchers have observed these changes in response to everything from maximal cycling bouts to a mere 20-minute stroll on the treadmill.

Increased blood flow to the brain during exercise may also explain how exercise induces these immediate cognitive benefits. More precisely, it is the nutrients (namely glucose and oxygen) carried by this blood flow that’s thought to boost our thinking. The animal research strongly supports this, but it’s much trickier to measure cerebral blood flow in response to exercise in us. I’m actually involved in a study at UMD, spearheaded by Dr. Carson Smith, that will try to do precisely that. In a nutshell, functional MRI will be used to try and compare cerebral blood flow before and after volunteers ride a stationary bike. I’ll let you know what we learn!

So, why don’t any of these stories make the news? Maybe, if exercise came in a little round pill.