A new scientific study has revealed that a simple measurement obtained from a routine blood test may help predict the risk of developing Alzheimer’s disease and dementia years before any symptoms appear in a patient.
The study was conducted by researchers at NYU Langone Medical School, who focused on the neutrophil-to-lymphocyte ratio. Neutrophils are a type of white blood cell and are among the first immune cells to respond when an infection or inflammation occurs. Their numbers rise quickly during illness, and this ratio can be easily obtained from a complete blood count, a common routine test.
To verify the idea, the researchers analyzed data from about 400,000 people across two health systems: the first included 285,000 patients from NYU hospitals, and the second included 85,000 patients from the Veterans Health Administration.
For each patient, they selected the earliest available measurement of the ratio, provided the person was at least 55 years old and the measurement had been taken before any Alzheimer’s diagnosis. They then tracked who would later be diagnosed.
The team found that patients with a higher ratio were more likely to develop Alzheimer’s and dementia over both the long and short term. A “higher” ratio meant above the average of all participants.
They also noted that the risk was greater in two groups: patients of Hispanic origin, for reasons that are not yet clear, and women.
One of the lead researchers said the findings are important for two reasons. First, this simple marker could be used alongside other risk factors, such as older age or family history, to identify those most at risk, refer them for more in-depth testing, and begin early treatment before symptoms emerge. Second, the results suggest that neutrophils may be actively involved in the development of dementia, rather than being merely a passing indicator.
Neutrophils are beneficial cells that help heal wounds and fight infection, but under some conditions they may cause tissue damage, especially in blood vessels—the same kind of damage observed in the brains of Alzheimer’s patients. Researchers found signs of neutrophil-driven inflammation in the brain tissue of Alzheimer’s patients, and experiments in mice also showed that neutrophils accelerate the progression of the disease.
With advancing age, the body may no longer be able to efficiently recycle and eliminate old neutrophils, causing them to accumulate and trigger chronic inflammation and damage.
So far, however, no definitive link has been proven between neutrophils and Alzheimer’s, because neutrophils survive only for a few days and must be studied from fresh blood samples, making research difficult. The team is now investigating whether neutrophils actually contribute to cognitive decline or are simply a marker, using measurements of their activity, brain imaging techniques, and cognitive tests.
If studies confirm that neutrophils cause dementia, they could become a new target for treatment.
For now, researchers hope this ratio will help develop simple, low-cost screening tools to identify those at risk before it is too late.
