Throughout every stage of your life, your brain is changing and evolving. From quick learning in your younger years to the wisdom and adaptability of adulthood, each phase reflects a shift in your brain’s structure, function, and connectivity.
Understanding your “brain age” can help shed light on your cognitive health, allowing you to make informed decisions to protect and enhance your brain – and stay sharp in the long run.
We can’t predict how our brains will change over time, but we can use advanced imaging tools – like a complete body scan – to help us prepare and detect conditions that may impact cognitive function.
How Your Brain Changes with Age
Have you ever noticed how children seem to learn and retain new information with ease? That’s because in those early years, the brain forms more than a million new neural connections every second. But that’s not the only thing that changes with your brain.
Structural Changes
Just as your hair turns grey and wrinkles start to show, your brain also begins to change as you age. Brain volume peaks in early adulthood and begins a slow, measurable decline from around age 35. A review of 56 longitudinal MRI studies put that loss at roughly 0.2 percent a year in your late thirties, accelerating to about 0.5 percent a year by age 60, and the rate keeps climbing after that. Small annual numbers that add up over decades, and they describe healthy people, not sick ones.
Shrinkage is not spread evenly. In a five-year study tracking healthy adults with repeat MRI scans, the largest losses showed up in the hippocampus, the cerebellum, the caudate nucleus and the association cortices, including the prefrontal regions that handle planning and judgement. Other areas barely moved. The primary visual cortex showed no measurable loss at all. Aging is selective about what it takes.
Neuron Changes
In those early years of life, your brain forms over a million new neural connections. However, as the brain ages, individual neurons could begin to contribute to the shrinkage and cortical thinning of the brain. As these connections between the brain begin to deteriorate, your learning and memory capabilities start to suffer.
Chemical Changes
The final changes our brains undergo as we age are all chemical. Across the dopamine system, receptor and transporter density falls by roughly 4 to 14 percent per decade, though a meta-analysis of 95 imaging studies found the brain’s actual ability to manufacture dopamine holds up well with age. Serotonin signalling also declines, and declines further when memory problems appear: in one imaging study of adults in their mid-sixties, those with mild cognitive impairment showed markedly lower serotonin transporter availability than healthy peers the same age. Mild cognitive impairment is a diagnosed condition, not a stage everyone passes through.
An Aging Brain and the Nervous System
Your nervous system is your body’s central control system, responsible for your movements, senses, and even your thoughts. Comprised of pathways that carry signals to your brain, called nerves, the nervous system experiences similar changes to the brain as you age.
Unfortunately, these changes can result in abnormal outcomes that may alter your quality of life.
Think of your nervous system like a network of electrical wires in a new home. In the beginning, the wires are fresh, the connections are fast, and respond with ease. However, as the house begins to age, the wires may fray and connections become loose, causing that light to take a bit longer to turn on than it used to – that is how your nervous system functions as you age.
As your nervous system ages, your brain and spinal cord lose nerve cells and weight. When this occurs, the nerves find it harder to communicate and carry signals to your brain and the rest of your body. Processing slows, recall takes a beat longer, and balance and gait shift with the decades. Those are ordinary features of an aging nervous system.
Alzheimer’s disease is not a stage of normal aging. Its two defining features are amyloid plaques, which accumulate between nerve cells, and neurofibrillary tangles of tau protein, which form inside them. Small amounts of both turn up in cognitively healthy older brains, and notably some people accumulate a great deal of both and never develop dementia at all. The widespread build-up that defines Alzheimer’s is disease, not a milestone everyone reaches.
What Researchers Actually Mean by Brain Age
In neuroimaging research, brain age is a specific measurement rather than a turn of phrase. Researchers train machine-learning models on MRI scans from thousands of healthy people, then use those models to predict a person’s age from the structure of their brain alone. The gap between predicted and actual age is the number being studied, and at a group level a gap in the older direction has been associated with conditions including Alzheimer’s disease.
It is worth being direct about what producing that number takes: a specific research imaging sequence, automated software that measures brain volumes region by region, and a validated model with large-scale normative data behind it. It is not something a radiologist reads off a scan, and it is not part of a standard MRI report, including ours. Researchers are also still working out how reliable it is for any one individual. Run the same scan through different software packages and you can get different answers.
So when this article talks about brain age, it means it in the everyday sense: how the brain changes across the decades of a life. We do not offer a brain age score, and you should be sceptical of anyone who offers you one as a verdict on your health.
Can a Scan Spot Early Alzheimer’s?
No. A screening MRI cannot diagnose Alzheimer’s disease and it cannot tell you whether you will develop it. No imaging scan can.
What a brain MRI shows is structure. It can reveal age-related volume loss, changes in white matter, and findings that have nothing to do with dementia, such as a previous silent stroke, a mass, or fluid build-up. Some of those are treatable, and some can themselves cause memory or balance symptoms that get mistaken for dementia. Those are worth knowing about.
But structural findings are not specific to Alzheimer’s. Brain volume decreases with age in healthy people, as this article has just described, and plenty of people with visible shrinkage never develop dementia. That is precisely why atrophy on a scan cannot serve as a warning sign for an individual. Diagnosing Alzheimer’s takes a clinical evaluation, cognitive testing, and biomarkers measuring amyloid and tau through specialised PET imaging, spinal fluid analysis or newer blood tests. None of those are part of a screening MRI.
If you are noticing memory changes, the right first step is a conversation with your doctor, not a scan you booked yourself.
What Genuinely Protects an Aging Brain
This is the part that is actually actionable, and it is more encouraging than the alternative.
The Lancet Commission on dementia concluded in its 2024 report that around 45 percent of dementia cases worldwide are potentially preventable or delayable by addressing 14 modifiable risk factors across a lifetime: hearing loss, untreated vision loss, high blood pressure, high LDL cholesterol, diabetes, obesity, smoking, excessive alcohol, physical inactivity, social isolation, depression, head injury, air pollution and limited education.
Several of those are cardiovascular and metabolic, which is territory a whole-body scan legitimately touches. That is where imaging fits into this conversation honestly: not as a brain age test or an Alzheimer’s test, but as one way of seeing the vascular and metabolic picture underneath a meaningful share of that 45 percent.
And the capacity to form new connections does not switch off with age. It continues, more slowly, for the rest of your life.
Schedule a Full-Body MRI Scan Near You
If you want a broad structural picture of your health while you are feeling well, that is what we offer, and we are happy to explain exactly what it does and does not cover before you book. Schedule your full-body MRI in Charleston, SC or talk to our team first.
This article is for general education and is not medical advice.
Frequently asked questions
What is brain age?
In research it is a specific measurement. Machine-learning models trained on MRI scans from thousands of healthy people predict a person’s age from brain structure alone, and the gap between predicted and actual age is what is studied. Producing it requires a research imaging sequence, automated volumetric software and a validated normative model. It is not something a radiologist reads off a scan and it is not part of a standard MRI report, including ours.
At what age does the brain start to shrink?
Brain volume peaks in early adulthood and begins declining from around age 35. A review of 56 longitudinal MRI studies put the loss at roughly 0.2 percent a year in the late thirties, accelerating to about 0.5 percent a year by 60 and continuing to climb. These are small annual figures describing healthy people, and they add up over decades.
Which parts of the brain age fastest?
Shrinkage is selective. A five-year study of healthy adults found the largest losses in the hippocampus, cerebellum, caudate nucleus and association cortices, including the prefrontal regions handling planning and judgement. Other areas barely changed, and the primary visual cortex showed no measurable loss at all.
Can an MRI detect early Alzheimer’s disease?
No. A screening MRI cannot diagnose Alzheimer’s or predict whether you will develop it. Brain shrinkage happens to healthy people with age, and plenty of people with visible atrophy never develop dementia, which is why it cannot serve as an individual warning sign. Diagnosis requires clinical evaluation, cognitive testing and biomarkers measuring amyloid and tau via PET, spinal fluid or newer blood tests.
What actually protects an aging brain?
The Lancet Commission concluded in 2024 that around 45 percent of dementia cases worldwide are potentially preventable or delayable by addressing 14 modifiable risk factors: hearing loss, untreated vision loss, high blood pressure, high LDL cholesterol, diabetes, obesity, smoking, excessive alcohol, physical inactivity, social isolation, depression, head injury, air pollution and limited education. The capacity to form new neural connections also continues throughout life.
Sources
- Human brain changes across the life span: a review of 56 longitudinal magnetic resonance imaging studies
- Regional brain changes in aging healthy adults: general trends, individual differences and modifiers
- Reduced dopamine receptors and transporters but not synthesis capacity in normal aging adults: a meta-analysis
- Ten Years of BrainAGE as a Neuroimaging Biomarker of Brain Aging: What Insights Have We Gained?
- Dementia prevention, intervention, and care: 2024 report of the Lancet standing Commission
