Routine Hemoglobin Tests May Signal Long-Term Dementia Risk

Study Links Abnormal Hemoglobin Levels to Higher Dementia Risk

A routine test for hemoglobin may provide early clues about future dementia risk up to 15 years in advance. Researchers presented these findings at the 39th European College of Neuropsychopharmacology (ECNP) Congress in Munich, with the full paper published in the Journal of Alzheimer's Disease.

The observational study tracked 316,542 Korean adults aged 40 and older who completed a national health screening between 2004 and 2005. Investigators monitored health insurance records through 2019 to identify new dementia diagnoses across five equal hemoglobin tiers.

Participants in the lowest 20 percent of hemoglobin measurements experienced a 16 percent higher rate of all-cause dementia compared to the reference group with the lowest incidence. Those in the top 20 percent showed a 7 percent increase in overall dementia diagnosis.

Risk Patterns Differed Across Dementia Subtypes and Sex

The observed risk varied considerably depending on the specific form of dementia diagnosed during the 15-year window. For Alzheimer's disease, an elevated risk appeared primarily among participants in the lowest 20 percent of hemoglobin levels, who experienced a 14 percent higher rate.

Vascular dementia exhibited a U-shaped risk curve at both extremes of red blood cell protein concentration. Individuals in the lowest tier faced a 19 percent higher risk, while participants in the highest tier had an 18 percent higher risk.

The relationship between hemoglobin levels and vascular dementia did not follow a simple pattern across all five groups. The overall associations were clearer and more consistent in women than in men.

What Hemoglobin Levels Signal in Routine Blood Work

Hemoglobin is the iron-rich protein in red blood cells responsible for transporting oxygen throughout tissues and the brain. Low readings routinely indicate anemia, whereas unusually high readings often stem from dehydration, smoking, or chronic heart and lung disease.

Lead researcher Dr. Hyun Soo Kim of Dong-A University College of Medicine noted that abnormal levels likely serve as a broader marker of physical vulnerability rather than a direct cause of cognitive decline. Standard complete blood counts already evaluate this marker during routine annual physical exams without requiring specialized imaging.

• Lowest hemoglobin quintile: 16 percent higher risk of all-cause dementia and 14 percent higher risk of Alzheimer's disease.
• Highest hemoglobin quintile: 7 percent higher risk of all-cause dementia and 18 percent higher risk of vascular dementia.
• Sex differences: associations between blood levels and cognitive outcomes were stronger and more consistent in female participants.

Observational Limits and What the Findings Mean for Patients

Observational records cannot establish that abnormal red blood cell proteins directly cause brain tissue deterioration. Early stages of undiagnosed dementia can cause frailty, weight loss, and altered nutritional status, which may reduce hemoglobin before cognitive symptoms become apparent.

Dr. Kim emphasized that patients should not take iron supplements or attempt to manipulate hemoglobin values on their own to prevent cognitive decline. Anyone with an abnormal reading should discuss the result with a physician to evaluate potential underlying causes.