Brain cells and their connections degenerate as we age; aerobic exercise sparks new growth to optimize brain function
If your brain isn’t actively growing, then it’s dying. Exercise is one of the few ways to counter the process of aging because it slows down the natural decline of the stress threshold.
Starting at about age forty, we lose on average five percent of our overall brain volume per decade, up until about age seventy, when any number of conditions can accelerate the process. According to psychiatrist and researcher Dr. John Ratey, people who stay involved and active as they age can slow down the degeneration.
What scientists have discovered
As we age, neurons in the brain get worn down from cellular stress. Synapses erode and eventually sever the connections. With the decrease in activity, the dendrites physically shrink back and wither. Losing a signal here or there isn’t such a big deal at first, because the brain is designed to compensate by rerouting information around dead patches in the network and recruiting other areas to help with trafficking. However, if the synaptic decay outpaces the new construction, that’s when you start to notice problems with mental or physical function, ranging from Alzheimer’s to Parkinson’s disease (depending on where the degeneration occurs).
As the synaptic activity decreases and dendrites retract, the capillaries feeding the brain shrink back as well, restricting blood flow. It can work the other way around too: if capillaries shrink back because you don’t get your blood pumping often enough, the dendrites follow suit. Either way, it’s a killer — without the oxygen, fuel, fertilizer, and repair molecules carried by the bloodstream, cells die.
Levels of nurturing neurotrophins — such as brain-growth factor (VEGF) — trail off as you age too, and production of the neurotransmitter dopamine slows down, undermining motor function as well as motivation. Meanwhile, the hippocampus is getting fewer and fewer new neurons to work with.
How does exercise prevent this deterioration?
Exercise sparks connections and growth among your brain’s cell networks: it increases blood volume, regulates fuel, and encourages neuronal activity and neurogenesis. Because the aging brain is more vulnerable to damage, anything you do to strengthen it has a more pronounced effect than it would on a young adult.
That’s not to say starting early isn’t important. If you have a better, stronger, more connected brain going over the hill, it will surely be more resilient and resist neuronal breakdown that much longer.
Exercise is preventive medicine as well as an antidote
A particularly important effect of exercise for older adults is that it rallies dopamine, which diminishes with age. This is a critical neurotransmitter in the context of aging because it’s the major signal bearer of the reward and motivation systems. Apathy can become a defining characteristic for older folks, and it’s particularly important to watch for when people move into retirement communities and nursing homes. Even in the best and homiest facilities, depression and a lack of motivation can set in as people feel they’re just waiting to die.
A research study led by neuroscientist Arthur Kramer at the University of Illinois was conducted to see if exercise caused structural changes in the brain in sedentary people ranging in ages from 60-79. MRI scans before and after the 6 month study showed that those with improved fitness had an increase in brain volume in the frontal and temporal lobes. The major implication is that exercise not only keeps the brain from rotting, but it also reverses the cell deterioration associated with aging. Read more about the study.