When it comes to protecting your brain, one of the most powerful things you can do is surprisingly simple:
Know your numbers.
We often think about dementia prevention in terms of memory tests and brain scans. But some of the earliest clues that something needs attention may already be sitting in your blood results.
Metabolic health, inflammation, insulin signalling, methylation and nutrient balance can all influence the environment in which your brain has to function.
And importantly, many of these factors are modifiable.
So, which numbers should you know?
What blood tests should I know for brain health?
There isn’t one blood test that can tell you whether you will develop dementia.
Instead, we look at a collection of markers that can help us understand potentially modifiable areas of risk.
Five that we frequently pay attention to are:
- HbA1c – longer-term blood glucose regulation
- Fasting insulin – how hard your body may be working to control glucose
- hs-CRP – a marker of systemic inflammation
- Homocysteine – associated with vascular and brain health
- Copper:zinc ratio – a useful indicator of mineral balance and oxidative/inflammatory processes
The important thing is not simply whether each result falls inside a laboratory reference range.
We want to understand the pattern, the trend and what may be driving it.
Why does HbA1c matter for brain health?
HbA1c gives us an indication of your average blood glucose exposure over approximately the previous 2–3 months.
It matters because:
- Diabetes is an established risk factor for dementia.
- Persistently higher glucose can affect blood vessels throughout the body, including those supplying the brain.
- Metabolic dysfunction can develop gradually, long before someone receives a diagnosis of diabetes.
- Watching HbA1c over time can help us identify an unfavourable trajectory earlier.
For prevention, we don’t only want to ask:
“Do you have diabetes?”
We also want to ask:
“Where is your glucose metabolism heading?”
Why should I know my fasting insulin?
Fasting insulin can sometimes tell us something that glucose and HbA1c alone don’t reveal.
Your blood glucose may still look relatively normal because your pancreas is producing more insulin to keep it there.
This matters because:
- Higher fasting insulin may be an early clue that insulin sensitivity is deteriorating.
- Insulin resistance can precede abnormal glucose or HbA1c.
- Insulin has important functions within the brain, not just in blood sugar control.
- Insulin resistance has been extensively investigated in relation to cognitive decline and Alzheimer’s disease.
So we often look at fasting glucose, HbA1c and fasting insulin together, rather than relying on a single metabolic marker.
What is hs-CRP and why does inflammation matter to the brain?
High-sensitivity C-reactive protein, or hs-CRP, is a blood marker that can help us identify low-grade systemic inflammation.
Inflammation matters because:
- Chronic inflammation can affect vascular and metabolic health.
- Higher circulating CRP has been associated with increased risk of all-cause dementia in observational research.
- Persistent inflammation may give us a reason to look more closely at what is driving it.
But hs-CRP needs context.
A recent infection, injury or inflammatory illness can temporarily raise it, so one elevated result doesn’t necessarily mean very much on its own.
We are often much more interested in the pattern:
Is hs-CRP repeatedly elevated when you are otherwise well?
If it is, the next question is why.
Why is homocysteine important for brain health?
Homocysteine is one of the markers we find particularly useful in brain-health assessment.
Higher homocysteine has been associated with:
- Cognitive decline
- Vascular disease
- White-matter changes
- Brain atrophy
- Increased dementia risk
Homocysteine can be influenced by:
- Folate
- Vitamin B12
- Vitamin B6
- Kidney function
- Genetics
- Diet and lifestyle
This is what makes it so interesting from a prevention perspective: it is potentially modifiable.
The VITACOG trial found that B-vitamin treatment lowered homocysteine and slowed brain atrophy in older adults with mild cognitive impairment, with particularly marked effects in people who began with higher homocysteine.
Not every trial has demonstrated a cognitive benefit from lowering homocysteine, so it isn’t as simple as taking a B-vitamin supplement.
But it is a number worth knowing.
What does the copper:zinc ratio tell us?
Copper and zinc are both essential nutrients. Neither is inherently “good” or “bad”.
What interests us is balance.
Copper and zinc are involved in:
- Antioxidant defence
- Immune regulation
- Inflammatory processes
- Enzyme activity
- Neurological function
Some observational research has found differences in the copper:zinc ratio in people with Alzheimer’s disease compared with cognitively healthy adults.
This is an emerging area and the evidence isn’t as established as it is for major dementia risk factors such as diabetes, hypertension or smoking.
We therefore don’t use copper:zinc ratio to predict dementia.
Instead, it can provide another piece of the biological puzzle when considered alongside other findings.
Is being within the “normal range” enough?
Not necessarily.
A laboratory reference range is primarily designed to identify results outside the expected range in a population. Prevention asks a slightly different question.
We may want to know:
- Is your HbA1c gradually increasing?
- Is your fasting insulin rising?
- Is hs-CRP persistently elevated?
- Is homocysteine higher than previously?
- Has your copper:zinc balance changed?
- Are several markers moving in the wrong direction together?
Sometimes three apparently normal results moving steadily in the wrong direction tell us more than one abnormal result.
That is why previous blood tests can be incredibly valuable.
Can these brain-health risk factors be changed?
Many can.
Depending on what is driving the result, potentially modifiable factors can include:
- Diet and glucose regulation
- Exercise and muscle mass
- Sleep
- Alcohol
- Smoking
- Blood pressure
- Weight and visceral fat
- Nutrient deficiencies
- B-vitamin status
- Inflammation
- Insulin resistance
The aim isn’t to chase perfect numbers.
It is to identify areas where we may be able to change the trajectory.
Can blood tests tell me if I am going to develop dementia?
No.
HbA1c, insulin, hs-CRP, homocysteine and copper:zinc ratio cannot predict whether an individual will develop dementia.
Brain health is influenced by many interacting factors, including:
- Genetics
- Cardiovascular health
- Metabolic health
- Hearing and vision
- Physical activity
- Smoking and alcohol
- Social connection
- Education and cognitive stimulation
- Depression
- Traumatic brain injury
- Environmental exposures
Blood biomarkers are therefore pieces of a much bigger picture.
When should I start thinking about dementia prevention?
Ideally, before you have symptoms.
There is an enormous difference between asking:
“Do I have dementia?”
and:
“What can I learn about my brain-health risk now?”
The second question can be asked years — potentially decades — earlier.
And that gives us something incredibly valuable:
time.
Time to investigate.
Time to make changes.
Time to measure again.
And time to see whether those changes are actually working.
What are the five numbers I should know for my brain?
If you want a simple place to start, know your:
- HbA1c
- Fasting insulin
- hs-CRP
- Homocysteine
- Copper and zinc
These numbers don’t tell you your future.
But they can tell us something valuable about where you are today — and where there may be opportunities to reduce modifiable risk.
At CogMission, that’s what prevention is about.
Don’t wait for your memory to become the problem before you start asking questions about your brain.
Know your numbers. Know where you stand. And, where possible, change the trajectory.