S2E2. More Risk Factors

Ugh. Just what we needed: more things that increase the likelihood of our developing dementia.   😦

The upside of this, though, is that more and more research is being done and we’re moving towards getting a handle on what’s really going on in our brains as we age. And since forewarned is forearmed, this is a good thing, right?

The list of risk factors was already pretty extensive before the most recent studies came out: age, head injury, smoking, excessive drinking, high cholesterol, diabetes, high blood pressure, insomnia, air pollution, obesity, depression, social isolation, lack of physical activity, strokes, hearing loss and lack of education, to name those at the top of the list.

Here’s one I just learned about last week: infectious diseases. The suggestion has been around since Alzheimer’s was first identified, but it was considered a fringe theory and relegated to a backwater of research. Now it’s receiving more attention.

The identified possible culprits are herpes, Lyme disease, and gingivitis. Each is able to cross the blood-brain barrier and invoke immune responses and inflammation which leave beta amyloid and tau proteins as by-products of the process. Those chemicals, in turn, form the plaques and tangles associated with dementia.

It made me wonder if, in a decade, we won’t be looking at having had COVID as a risk factor. After all, symptoms of COVID include brain fog and loss of taste and smell, all of which are brain functions.

Apparently, though, COVID does not cross the blood-brain barrier, so it’s mechanism of action must be different from the others. It’s been suggested that it might weaken the barrier enough to let other microbes cross which then triggers the immune response. The research is ongoing. 

But infections aren’t the only newly-identified risk factors. It now appears that having cataracts is correlated with developing dementia, too.

In this case, it isn’t immediately apparent what the connection might be. How can having a cloudy lens in your eye impair cognitive performance?

Two possible pathways are suggested. First, having difficulty seeing might lead to more social isolation (e.g., not driving at night to be with friends). Alternatively, when your lenses are clouded, less light passes through them. This results in a drop in overall electrical stimulation to your brain.

These two ideas are roughly the same as those proposed for why hearing loss is a risk factor: (1) difficulty following conversations leads to withdrawal and social isolation and (2) reduced auditory stimulation leads to an overall decline in brain activity.

What do I make of all this? To me, there seems to be an overarching pattern here: whatever reduces brain activity increases the risk for developing dementia. Conversely, things you do that stimulate brain activity are protective.

If this is the case, then we can see why having cataract surgery, wearing hearing aids, listening to music, exercising, social engagement, reading books and learning new skills are all protective.

It really looks like we might be looking at a “use it or lose it” scenario. Or more accurately, “use it or lose it faster” because we will all experience declines in our cognitive performance as we age, so the goal is to slow down that process in order to live a long, healthy life and then die before we meet the criteria for dementia.

But this stimulation theory does not, of course, explain everything. Another group of risk factors appears to involve the ability to pump a steady supply of well-oxygenated blood to the brain. Just this past month, a study was released correlating higher resting heart rate with an increased risk of dementia. It’s no wonder that behaviors that are heart-healthy are also brain-healthy. 

I’m seeing a third cluster that centers around the process of removing debris from your brain. It appears you need to provide the chemical building blocks your brain needs to clean up the mess left after an immune response has been triggered. This cluster includes doing things that can prevent the debris from forming in the first place, like managing stress and providing the opportunity for your brain’s maintenance system to do its job, i.e., getting a good nights sleep.

Given just this much information, it’s beginning to look a lot like dementia isn’t usually caused by just one thing. It’s more likely that it’s born of a lifetime of insults, from an assortment of causes whose effects lie latent for years and then emerge as we get older and reduce our daily activity level and the cognitive stimulation that comes with it. 

I’m starting to see something take shape out of this great fog of all we don’t yet know about dementia. True…it’s just a few broad brush strokes…but it’s beginning to make some sense.

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