High Alzheimer’s Markers? Your Kidneys Might Be to Blame, Not Your Brain

If you've been following the latest developments in Alzheimer's research, you've probably heard about blood-based biomarkers. These tests measure proteins associated with Alzheimer's disease right from a simple blood draw, making them far more accessible than traditional methods like spinal taps or brain scans. 

But elevated levels of these biomarkers don't always tell the whole story about what's happening in your brain. 

The study tracked over 2,000 dementia-free adults with an average age of 72, measuring both their kidney function and several key Alzheimer's biomarkers, including tau proteins, amyloid beta, neurofilament light chain (NfL), and glial fibrillary acidic protein. Kidney function was assessed using estimated glomerular filtration rate (eGFR), which essentially measures how well your kidneys filter waste from your blood.

What the researchers found was striking. People with lower kidney function had significantly elevated levels of nearly all the Alzheimer's biomarkers tested. The strongest connection showed up with neurofilament light chain, a protein that indicates general brain cell damage. 

So why would struggling kidneys lead to higher Alzheimer's biomarkers? The answer likely comes down to basic biology. 

Your kidneys are responsible for filtering waste products and proteins out of your bloodstream. When they're not working optimally, these proteins can accumulate in your blood, including the ones we associate with Alzheimer's disease. Think of it like a drainage system that's partially clogged. The backup doesn't necessarily mean more waste is being produced; it just means less is being cleared away.

This is particularly important for the neurofilament light chain. While elevated levels of this protein can indicate neurodegeneration, it's not specific to Alzheimer's. It shows up when any kind of nerve damage is happening. 

The study found that people with both impaired kidney function and high neurofilament light chain levels faced nearly double the dementia risk compared to those with healthy kidneys and similarly elevated biomarkers. 

This suggests that kidney problems might accelerate the clinical expression of existing brain pathology rather than causing new damage.

The good news here is that impaired kidney function alone didn't increase dementia risk in this study. That's reassuring for the millions of older adults living with some degree of kidney decline, which is actually a normal part of aging. 

This study doesn't mean blood-based Alzheimer's tests are unreliable. Rather, it shows they need to be interpreted within the full context of your health, including kidney function.