Neutrophil Levels and Early Immune Changes Signal Future Alzheimer’s Risk

New research from NYU Langone Health indicates that elevated levels of neutrophils, a type of white blood cell, may signal an increased risk of developing Alzheimer’s disease and related dementias years before cognitive symptoms appear.

The study, published in the journal Alzheimer’s & Dementia on April 3, 2026, analyzed neutrophil to lymphocyte ratio (NLR) data from nearly 400,000 patients across two major healthcare systems. Researchers found that a high NLR — reflecting elevated neutrophil levels relative to lymphocytes — was associated with increased dementia risk, even in individuals showing no signs of cognitive impairment.

Study Design and Key Findings

Led by Tianshe (Mark) He, PhD, a data scientist in the Department of Psychiatry at NYU Grossman School of Medicine, the research team examined data from approximately 285,000 patients at four NYU Langone hospitals and nearly 85,000 patients from the Veteran’s Health Administration. For each participant, scientists selected the earliest available NLR measurement taken after age 55 that met study criteria.

“Our study is the first large-scale investigation showing that neutrophil metrics are associated with increased risk of dementia in humans,” said Dr. He. “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.”

Understanding the Neutrophil to Lymphocyte Ratio

The neutrophil to lymphocyte ratio (NLR) is a simple biomarker derived from a routine complete blood cell count. Neutrophils are among the immune system’s first responders, increasing in number during infection and inflammation. Lymphocytes, another type of white blood cell, play key roles in adaptive immunity. An elevated NLR suggests a shift toward innate immune activity and may reflect chronic inflammation or immune dysregulation.

Implications for Early Detection and Research

Because NLR is routinely measured in clinical settings, the findings suggest it could serve as an accessible tool for identifying individuals at higher risk for Alzheimer’s disease long before memory loss or confusion occurs. Researchers emphasize that while the association is strong, the study does not prove that elevated neutrophils cause dementia — only that they are linked to increased risk.

Study Limitations and Future Directions

“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.”

Tianshe (Mark) He, PhD, NYU Grossman School of Medicine

The researchers note that the study was observational and cannot establish causality. Future work will need to investigate whether modifying neutrophil activity or reducing inflammation could influence dementia risk. The team also plans to explore whether NLR changes correlate with specific biomarkers of Alzheimer’s pathology, such as amyloid-beta or tau accumulation.

Jaime Ramos-Cejudo, PhD, study co-senior author and assistant professor in the Departments of Psychiatry and Neurology at NYU Grossman School of Medicine, highlighted the value of leveraging existing clinical data. “Using data from routine blood tests allows us to examine immune markers in large, real-world populations,” he said. “This approach could help bridge the gap between laboratory findings and clinical application.”

Broader Context in Neuroimmunology

The study adds to growing evidence that immune system dysfunction plays a role in neurodegenerative diseases. While Alzheimer’s has long been viewed primarily through the lens of neuronal damage and protein buildup, increasing research suggests that chronic inflammation and altered immune responses may contribute to disease onset and progression.

“Circulating white blood cells called neutrophils are some of the immune system’s first responders. Their numbers shoot up during infection and inflammation, shifting the ratio of neutrophils to other types of immune cells in the blood.”

PR Newswire, April 21, 2026

As of April 22, 2026, no clinical guidelines recommend using NLR to assess Alzheimer’s risk. Experts caution that further validation is needed before such a measure could be considered for screening or diagnostic use. Nevertheless, the findings open a new avenue for understanding how peripheral immune activity might influence brain health over time.