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A study tracking 316,542 Korean adults found that people with very low hemoglobin—and, for some outcomes, very high levels—were more likely to receive a dementia diagnosis over as long as 15 years. The observational findings do not show that hemoglobin causes dementia or that changing its level can prevent the disease.
A study of 316,542 adults in South Korea found that hemoglobin levels measured during routine health screening were associated with dementia diagnoses recorded over the following years. The research, presented at the 39th ECNP Congress and published in the Journal of Alzheimer’s Disease, suggests a possible long-term health marker, but does not show that hemoglobin levels cause dementia or predict an individual’s outcome.
The researchers examined adults aged 40 and older who attended national health screenings in 2004 and 2005. They grouped participants into five categories based on hemoglobin levels, then used national health insurance records to identify new dementia diagnoses through the end of 2019. Follow-up lasted up to 15 years.
Compared with the group that had the lowest dementia rate, participants in the lowest fifth of hemoglobin levels had a 16% higher risk of all-cause dementia. Those in the highest fifth had a 7% higher risk. These are relative differences reported by the study, not estimates of an individual’s chance of developing dementia.
The pattern varied by diagnosis. For Alzheimer’s disease, the elevated risk was mainly seen among people in the lowest hemoglobin group, whose risk was 14% higher than the reference group. For vascular dementia, the lowest group had a 19% higher risk and the highest group an 18% higher risk. Researchers said the vascular dementia association did not follow a simple progression across all five categories. The relationship was also clearer and more consistent in women than in men.
Hemoglobin is a protein in red blood cells that carries oxygen through the body. Low levels can be associated with anemia; unusually high levels may be associated with several conditions or factors, including smoking, dehydration, and lung or heart disease. The study did not establish which, if any, of these factors accounted for the observed dementia patterns.
What Routine Blood Counts Could Reveal
Hemoglobin is already measured in many standard blood tests, making it a readily available measure that can be examined in existing medical records. The findings may help researchers investigate how general physical health, oxygen transport, and brain health relate over time. They do not mean that a routine blood count can diagnose dementia or provide a reliable forecast for a particular patient.
Lead researcher Dr. Hyun Soo Kim, an assistant professor at Dong-A University College of Medicine in Busan, said abnormal levels may be a visible marker of broader physical vulnerability relevant to brain health. He said the results do not show that hemoglobin itself causes dementia. The distinction matters: a marker can be associated with an outcome without being its cause or a useful target for treatment.
The study also does not support taking iron supplements or trying to raise or lower hemoglobin to prevent dementia. Dr. Kim said an abnormal result should instead be discussed with a doctor, since it may point to an underlying health issue that needs attention.
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How Researchers Tracked Dementia Diagnoses
The research drew on a large national screening cohort in South Korea. Hemoglobin was measured at a single screening period in 2004–2005, and subsequent diagnoses were identified through health insurance records until 2019. That design let researchers compare long-term outcomes across hemoglobin groups, but it does not show that the blood measure remained unchanged during follow-up.
The study was observational: researchers looked for patterns in existing health data rather than assigning participants to different hemoglobin levels. As Dr. Kim noted, this can identify associations but cannot establish direct cause and effect. The researchers also raised the possibility that early, undiagnosed dementia processes could affect nutrition, frailty, weight, or anemia, influencing the association in the opposite direction.
Commenting on the work, Dr. Lindsey Sinclair of the University of Southampton said evidence increasingly points to links between physical and brain health. She said more research is needed to determine whether the association applies to people from a wider range of backgrounds and what, if anything, can reduce dementia risk among people with very low or high hemoglobin.
Cause, Prediction and Wider Applicability
The study cannot show whether hemoglobin levels contribute to dementia, reflect other health conditions, or are partly affected by early changes that precede diagnosis. The researchers also did not establish a clinical threshold that could be used to predict dementia risk for an individual. Although the cohort was large, it consisted of adults screened in South Korea, so the results may not apply equally to populations with different backgrounds or health profiles.
Further work is needed to clarify why the patterns differed by dementia type and sex, and whether they persist when other health factors are considered. The reported percentages describe relative risk compared with a reference group; the supplied findings do not provide the absolute likelihood of dementia for each hemoglobin category.
Further Studies Must Test the Link
The next step is research in other populations and studies that examine possible explanations for the association, including underlying illness and changes that may occur before dementia is diagnosed. Researchers will also need to determine whether hemoglobin adds useful information beyond other health measures and whether any clinical response improves outcomes.
For now, the findings are a research lead, not a change to dementia screening or treatment guidance. People with unusually low or high hemoglobin should discuss the result with a qualified health professional, as Dr. Kim advised, rather than trying to alter it for dementia prevention.
Key Questions
Does low hemoglobin cause dementia?
The study does not establish that low hemoglobin causes dementia. It found an association in an observational cohort, which cannot determine cause and effect.
What did the study find about high hemoglobin?
Participants in the highest fifth had a 7% higher relative risk of all-cause dementia than the reference group. For vascular dementia, the highest fifth had an 18% higher risk; the pattern across all five groups was not simple.
Should I take iron to reduce dementia risk?
No prevention benefit was tested. Lead researcher Dr. Kim specifically cautioned against interpreting the findings as advice to take iron or deliberately change hemoglobin levels. Discuss abnormal test results with a qualified health professional.
Can a routine blood test predict whether I will develop dementia?
No. The study identified group-level associations, not a validated test for predicting an individual’s outcome or diagnosing dementia.
How long were participants followed?
Researchers tracked new dementia diagnoses in national health insurance records from the 2004–2005 screening period through the end of 2019, for up to 15 years.
Source: rss
