A common blood marker linked to inflammation may indicate a person's risk of developing Alzheimer's disease years before symptoms appear. Scientists at NYU Langone Health found that higher levels of neutrophils, a type of white blood cell, were associated with an increased likelihood of developing dementia. This discovery suggests that a routine lab value could help identify at-risk individuals. It also raises questions about the role of immune cells in the disease's progression.
Neutrophils are part of the body's initial immune response to infection and inflammation. Their numbers can increase rapidly when the immune system is activated. Doctors can measure the balance between neutrophils and other immune cells using the neutrophil to lymphocyte ratio (NLR), a standard value from a complete blood count.
The research, published in *Alzheimer's & Dementia*, analyzed NLR data from nearly 400,000 patients. This included approximately 285,000 patients from four NYU Langone hospitals and about 85,000 individuals from the Veteran's Health Administration. The study focused on NLR measurements taken when patients were at least 55 years old and before any dementia diagnosis. Researchers then tracked whether these individuals developed dementia during the study period.
Across both patient groups, higher NLR levels consistently correlated with an increased risk of developing Alzheimer's or other forms of dementia. This association was observed for both short-term and long-term risk. The analysis also indicated stronger associations in Hispanic patients and women across both healthcare systems. While a high NLR alone may not definitively predict dementia, it could, when combined with other risk factors, help identify individuals who might benefit from closer monitoring or early interventions.
These findings support the idea that neutrophils may actively contribute to the disease process. Neutrophils are crucial for fighting infections and repairing tissue, but they can also cause damage under certain conditions. Signs of neutrophil-driven inflammation have been found in the brains of Alzheimer's patients. Animal studies suggest these cells can accelerate disease progression. Researchers are continuing to investigate whether neutrophils directly contribute to cognitive decline.
Further studies will determine if neutrophils are merely a marker of Alzheimer's disease or if they actively cause dementia progression. If they are causative, neutrophils could become a therapeutic target. In the interim, the neutrophil to lymphocyte ratio could serve as a gateway diagnostic tool for individuals at risk of Alzheimer's and dementia. This could lead to more in-depth testing and interventions before cognitive decline becomes apparent.
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