Why You Should Track Subtle Heart Changes If You Are At Genetic Risk Of Alzheimer’s
Heart health and brain health are often treated as separate concerns, but new research suggests they're far more intertwined than we realized, especially for people with a genetically higher risk of Alzheimer's.
A 2026 study published in Alzheimer's & Dementia was the first longitudinal study to examine the relationship between subtle cardiac dysfunction and brain atrophy over time. The researchers followed 756 middle-aged and older adults for up to 11 years and found that lower cardiac output (your heart pumping less blood minute), was linked to faster brain shrinkage over time. But, this association was only significant in people who carry the APOE-ε4 gene variant, the most well-known genetic risk factor for Alzheimer's disease.
About the study
Researchers from the Vanderbilt Memory and Alzheimer's Center used echocardiograms (heart ultrasounds) to measure cardiac output at the start of the study, then tracked brain volume changes with MRI scans throughout the follow-up period.
Participants were adults aged 50 to 92 who had no history of stroke, dementia, or heart failure. The data revealed that, among APOE4 carriers, lower baseline cardiac output was linked to more expansion of fluid-filled spaces in the brain over time.
This is a sign that surrounding brain tissue, particularly in the memory center of the brain, is shrinking. Interestingly, no significant association was found between cardiac output and brain volume changes among people who did not carry the APOE4 gene.
Wait, what is the APOE4 gene?
Why APOE4 carriers are more vulnerable
Not everyone is equally sensitive to subtle drops in heart pumping power. The APOE4 gene variant appears to make the brain more sensitive to even small reductions in blood flow.
The APOE4 gene affects specialized brain support cells and is associated with a less effective barrier for keeping harmful substances out of the brain. When blood flow dips even slightly, this filter works even less efficiently, leaving brain cells more exposed to damage. Over time, this vulnerability may accelerate the kind of brain tissue loss that precedes cognitive decline.
The effects were most pronounced in the brain's memory center, the region most closely associated with early Alzheimer's changes. In a snapshot view of the data, APOE4 carriers with lower cardiac output also had smaller total brain volume, as well as reduced volume in the temporal lobe (the brain region involved in memory and language) and the occipital lobe (the region at the back of the brain that processes vision).
The researchers say the brain's memory center may be particularly susceptible to reduced blood flow because it has a lower density of blood vessels compared to other brain regions, making it more sensitive to even subtle fluctuations in circulation.
In short, a heart that's pumping a little less efficiently may not be a problem for most people, but for APOE4 carriers who are already struggling with a weakened brain barrier, it can further increase risk over years and decades.
What this means for you
The study's authors suggest that cardiac screening, even in middle age before any symptoms appear, could become a useful tool for identifying people at elevated risk for brain degeneration. This could be especially important for APOE4 carriers. If you're thinking about getting your heart tested, here are a few things worth knowing:
- Cardiac output is measurable: An echocardiogram, which is just an ultrasound of your heart, can assess how efficiently your heart is pumping. If you carry the APOE4 gene and have concerns about brain health, it's worth discussing this test with your doctor.
- The values in this study were in the normal range: Participants didn't have heart failure or overt cardiac disease—subtle differences in cardiac output still effected the brain. This reinforces the idea that optimizing cardiovascular health, not just avoiding disease, matters for the brain.
- Heart-healthy habits support brain health: Regular aerobic exercise, blood pressure management, not smoking, and maintaining a healthy weight all support cardiac output and cerebral blood flow. These traditional "heart health" strategies will benefit your brain, too.
The takeaway
For most people, a slightly lower-than-optimal cardiac output isn't a concern. But this research changes the definition of "heart health" for the roughly 25% of the population who carry the APOE4 gene. It shifts the goal from avoiding a heart attack, to maintaining peak cardiac health to protect the brain from slow degeneration.
If you carry the gene, talk to your doctor about getting an echocardiogram at your next visit. And if you are curious the APOE4 gene, think about if getting tested is the right move for you.