A new study suggests that a simple blood marker may help identify the risk of Alzheimer’s disease long before symptoms appear. The marker is the neutrophil-to-lymphocyte ratio (NLR)—a parameter that can be easily measured in a standard blood test and reflects the state of the immune system.

The study, conducted by researchers at NYU Langone Health and the NYU Grossman School of Medicine, is based on data from nearly 400,000 patients across two large healthcare systems. The findings were published in the journal Alzheimer’s & Dementia.

Researchers analyzed NLR values in patients over the age of 55, using only measurements taken before any diagnosis of dementia. They then tracked whether these individuals developed the disease in subsequent years.

The analysis showed that elevated NLR is statistically associated with both short-term and long-term risk of developing Alzheimer’s disease and other forms of dementia. Notably, increased neutrophil levels were observed before any signs of cognitive decline, making this marker potentially valuable for early detection.

The study also found that the link between high NLR and dementia risk is stronger in women and in patients of Hispanic origin. The reasons for this are not yet clear and may involve both genetic factors and social determinants, including access to healthcare.

Researchers emphasize that this marker alone is not sufficient for diagnosis, but when combined with other risk factors it may help identify individuals who require more in-depth evaluation before symptoms appear.

Of additional interest is the possible role of neutrophils themselves in disease development. These cells are among the first responders of the immune system and are involved in inflammatory processes. While essential for immune defense, their activity can also contribute to tissue damage, including blood vessels, a feature already observed in Alzheimer’s disease.

At this stage, the neutrophil-to-lymphocyte ratio is considered a promising tool for early risk detection that could help initiate diagnosis and preventive measures long before cognitive impairment develops.