Routine Blood Tests May Predict Long-Term Dementia Risk

Routine blood screening tests and advanced genetic markers are offering doctors new ways to estimate long-term dementia risks and track cognitive impairment. Recent findings reveal that common hemoglobin checks and blood protein levels can signal vulnerability years before symptoms fully develop.

Blood Hemoglobin Levels and Long-Term Dementia Risk in Korean Adults

A large-scale observational study following 316,542 Korean adults aged 40 and over has linked routine blood screening results to future dementia diagnoses. Participants underwent national health screenings in 2004–2005, and national health insurance records tracked new dementia diagnoses through the end of 2019, spanning up to 15 years of follow-up.

Researchers divided participants into five distinct groups based on hemoglobin levels. Individuals in the lowest 20% of hemoglobin levels faced a 16% higher risk of all-cause dementia compared to the reference group with the lowest dementia rate, while those in the highest 20% experienced a 7% higher risk.

The pattern shifted depending on the specific type of dementia. For Alzheimer’s disease, elevated risk concentrated primarily among the 20% of individuals with the lowest hemoglobin levels, showing a 14% increase over the reference cohort. For vascular dementia, which stems from reduced blood flow to the brain, participants in the lowest 20% group faced a 19% higher risk, and those in the highest 20% group had an 18% greater risk. Researchers also noted that the association appeared clearer and more consistent in women than in men.

Routine Blood Tests May Predict Long-Term Dementia Risk — Photo: miragenews.com

Hemoglobin serves as the primary protein in red blood cells responsible for transporting oxygen throughout the body. While low levels often indicate anemia, unusually high levels can point toward smoking, dehydration, heart or lung disease, or other medical conditions. Experts emphasize that abnormal readings should prompt a conversation with a physician rather than self-treatment with iron supplements.

Combining Blood p-tau217 Biomarkers and APOE-ε4 Gene Status

In a separate multi-study analysis published on September 9, 2026, in Lancet Neurology, researchers examined the interplay between blood levels of the protein p-tau217, different forms of the APOE gene, and cognitive impairment risk. Led by Dr. Richard Mayeux of Columbia University and funded by the National Institutes of Health, the study pooled data from seven prospective cohort studies involving more than 8,500 older adults across Canada, the Dominican Republic, and the United States between 1992 and 2025.

The findings demonstrate that combining blood p-tau217 levels together with APOE-ε4 gene status significantly improves the ability to predict dementia risk and estimate when symptoms may appear. Participants carrying the APOE-ε4 gene variant alongside high blood concentrations of p-tau217 faced an especially high likelihood of developing cognitive impairment. Furthermore, the time to cognitive impairment with increasing p-tau217 decreased almost twice as fast in APOE-ε4 carriers as in non-carriers, revealing a distinct three- to four-year window between elevated biomarker levels and the onset of observable symptoms.

Researchers note that these predictive links appeared stronger in non-Hispanic White participants than in individuals from other racial or ethnic backgrounds, reflecting known ancestry-based variations in APOE-ε4 risk.

Experts Caution Observational Data Cannot Establish Direct Causation

Independent experts emphasize that both approaches remain observational and cannot establish direct causation. Commenting on the hemoglobin findings, Dr. Lindsey Sinclair of the University of Southampton noted that physical health and brain health remain tightly intertwined, pointing out that mid-life medical and lifestyle interventions are critical for reducing later risk.

Similarly, investigators involved in the p-tau217 and APOE research highlight that early, undiagnosed dementia processes may contribute to physiological changes such as weight loss, frailty, or anemia.