Routine Blood Count Ratio Linked to Future Alzheimer’s and Dementia Risk

Alzheimer’s disease and related dementias develop over years, making it difficult to identify at-risk patients before symptoms appear. Clinicians therefore need widely available laboratory markers that can flag risk early, and inflammation-derived indices from routine blood counts are attractive because they are already part of standard care. A new study shows that a high neutrophil-to-lymphocyte ratio measured from a complete blood cell count is associated with an increased future risk of Alzheimer’s disease and dementia.

NYU Langone Health (New York, NY, USA) researchers evaluated the neutrophil-to-lymphocyte ratio (NLR), an immune metric reflecting the balance between circulating neutrophils and lymphocytes. The ratio shifts upward during infection and inflammation and is easily derived from a complete blood cell count (CBC), which clinicians use to diagnose infection and other immune conditions. The investigation, published online April 3, 2026, in Alzheimer’s & Dementia, analyzed nearly 400,000 patient records from two health care systems.

Image: An elevated neutrophil-to-lymphocyte ratio (NLR), a rato easily obtained from a routine blood count, was associated with both short- and long-term Alzheimer’s risk (photo credit: 123RF)

The analysis included approximately 285,000 patients from four NYU Langone hospitals and nearly 85,000 patients from the Veterans Health Administration. For each participant, investigators selected the earliest NLR meeting study criteria: age of at least 55 years, measurement within the study timeframe, and an NLR obtained before any Alzheimer’s disease or dementia diagnosis. Researchers then assessed whether a dementia diagnosis occurred within the study window, using a data/statistical analysis approach.

Across both populations, an elevated NLR was significantly associated with both long‑term and short‑term risk of Alzheimer’s disease and related dementias. High NLR was defined relative to each cohort’s median value. The risk signal was stronger among Hispanic patients and among women in both health systems. Investigators noted that an elevated NLR alone is unlikely to be sufficient to predict future dementia, but in combination with other risk factors it could help identify individuals who warrant more comprehensive evaluation before cognitive decline becomes apparent.

The study team, which included collaborators affiliated with the VA Boston Healthcare System’s Cooperative Studies Program, highlighted two broader implications. First, the findings add to growing evidence that neutrophils may play a role in dementia progression, as these cells can contribute to vascular-level tissue damage observed in Alzheimer’s disease. Neutrophil-driven inflammation has also been identified in patient brain pathology, and animal studies show that increased neutrophil activity can accelerate disease.

Second, a definitive mechanistic link has not yet been established, in part because neutrophils are short-lived and require analysis in fresh blood samples. Ongoing research is therefore integrating measures of neutrophil activity with brain imaging techniques, including positron emission tomography (PET) and diffusion magnetic resonance imaging (MRI), alongside cognitive assessments.

“Our study is the first large-scale investigation showing that neutrophil metrics are associated with increased risk of dementia in humans. Neutrophil elevation is happening before any evidence of cognitive decline, which makes a compelling case for studying whether neutrophils are actively contributing to disease progression,” said Tianshe (Mark) He, PhD, a data scientist in the Department of Psychiatry at NYU Grossman School of Medicine.

“These and future studies will show whether neutrophils are just a marker of Alzheimer’s disease or are actively causing dementia progression — in which case, they could make a compelling therapeutic target,” said Jaime Ramos-Cejudo, PhD, assistant professor in the Departments of Psychiatry and Neurology at NYU Grossman School of Medicine.

"In the meantime, we hope the neutrophil to lymphocyte ratio can contribute to gateway diagnostic tools for people at risk of developing Alzheimer’s and dementia, so they can get more in-depth testing and interventions long before they experience cognitive decline,"  Dr. Ramos-Cejudo, who also serves as director of the Vascular and Immune Dysfunction in Aging and Alzheimer’s Disease (VIDA) lab at NYU Langone.

Related Links
NYU Langone Health
NYU Grossman School of Medicine