An aging brain is not simply a failing brain.
It’s a changing brain
Some of those changes are expected, natural adaptations over time.
Others are the result of stressors we can actually modify — if we understand them.
Let’s start with what we see clinically. In the clinic, when we follow people from their seventies into their eighties, we notice something interesting: People don’t age at the same speed.
Between about age 70 and 83, the gap widens.
Some brains stay surprisingly sharp.
Others decline rapidly — memory, attention, and even personality seem to shift.
The question is: why?
THREE BIG FORCES
There are three major forces that shape how the brain ages:
- Number one: inflammation.
- Number two: oxidative stress.
- Number three: mitochondrial decline — which is how our cells produce energy. These three are deeply connected. You can think of them as a triangle that either supports the brain, or slowly wears it down.
When you put those three together, you begin to understand why two people of the same age can have very different brain trajectories.
Chronic inflammation — especially from poor metabolic health, poor sleep, and chronic stress — is like a low-grade fire. You don’t always feel it as pain, but it’s there.Over years and decades, that fire changes the way neurons function, and how they talk to each other.
Oxidative stress is the second piece.
When our brain cells burn fuel, they generate reactive byproducts — what people sometimes simply call “free radicals.”
In a healthy system, our antioxidant defenses clean those up.
In an overwhelmed system, that clean-up crew falls behind.
Proteins misfold, membranes are damaged, and over time, this pushes vulnerable neurons closer to failure.
The third piece is mitochondrial decline. Mitochondria are the energy factories of our cells.
Aging mitochondria become less efficient. They produce less energy, and more of those reactive byproducts.
In high-demand areas of the brain — memory, movement, attention — that loss of energy really matters.
GENES VS. ENVIRONMENT
Now, what about genetics?
Yes, genes matter.
We all carry risk factors — for Alzheimer’s disease, for Parkinson’s, for vascular disease
But after about age 70, what we see more and more in the data is this:
Lifestyle and environment begin to compete with, and sometimes outweigh, pure genetics.
Two people with similar genetic risk can end up in completely different places.
One person is physically active, sleeps reasonably well, eats in a way that keeps inflammation lower, and stays socially engaged.
The other is sedentary, isolated, chronically sleep-deprived, and dealing with uncontrolled blood sugar or blood pressure.
They may share genes, but they do not share the same internal chemistry.
I often tell patients:
Your brain lives in the body you give it.
What the body experiences, the brain swims in.
NORMAL VS. NOT NORMAL
Patients and families often ask:
“What’s normal aging, and what’s not?”Some slowing of recall — taking a bit longer to find a name or a word — can be part of normal aging.
But difficulty keeping track of conversations, getting lost in familiar places, or repeating the same question without awareness — those are not “just getting older.”
Those are signals, and we should treat them that way.
In this series, we’ll keep coming back to this idea:
Signals.
The brain doesn’t send us a single, clear alarm bell.
It sends us clusters of subtle signals:
Sleeping worse.
Feeling more apathetic.
Struggling to follow complex instructions.
Needing more help with everyday tasks.
When those signals show up together, it’s time to look deeper.