TL;DR
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A long-term study of 316,542 adults in South Korea found that hemoglobin levels recorded in routine health screenings were associated with dementia diagnoses over as many as 15 years. The observational findings do not show that hemoglobin causes dementia or that changing its level prevents the condition.
A study of 316,542 South Korean adults found that unusually low—and, for some dementia outcomes, unusually high—hemoglobin levels on routine health screenings were associated with later dementia diagnoses. The research, presented at the 39th ECNP Congress and published in the Journal of Alzheimer’s Disease, identifies a possible long-term health marker, but does not show that hemoglobin levels cause dementia or that changing them would prevent it.
The researchers used national health screening data collected in 2004 and 2005 for adults aged 40 and older, then linked it to national health insurance records to identify new dementia diagnoses through the end of 2019. Follow-up lasted as long as 15 years. Participants were divided into five groups according to their hemoglobin levels, from the lowest fifth to the highest fifth.
Compared with the group that had the lowest dementia rate, people in the lowest hemoglobin fifth had a 16% higher risk of all-cause dementia; those in the highest fifth had a 7% higher risk. For Alzheimer’s disease, the reported association was concentrated among people in the lowest fifth, whose risk was 14% higher than the reference group’s.
For vascular dementia, the lowest hemoglobin fifth had a 19% higher risk, while the highest fifth had an 18% higher risk. The pattern across the five groups was not simple for vascular dementia. Researchers also reported that associations were clearer and more consistent in women than in men. The report does not establish that these differences apply to people outside the study population.
What Routine Hemoglobin Results Could Signal
Hemoglobin is a protein in red blood cells that carries oxygen through the body. Because it is already measured in many standard blood tests, the study raises the possibility that existing medical records could help researchers examine how whole-body health relates to brain health over time. It does not establish a new dementia screening test or show that a hemoglobin result can predict an individual person’s future.
The findings may be relevant to research because dementia develops over time and accessible measures could help identify health patterns worth investigating. But the observed differences are associations, not proof of a mechanism or a prevention strategy. A person’s dementia risk cannot be determined from the study’s group-level percentages alone.
Hemoglobin outside a usual range can have many possible explanations. The study’s lead researcher, Dr. Hyun Soo Kim, said an abnormal result should be discussed with a doctor because it may point to an underlying health issue. He cautioned against interpreting the results as a reason to take iron supplements or to try to raise or lower hemoglobin to prevent dementia.
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How the Korean Study Tracked Risk
The study drew on health screening and insurance records for a large cohort of adults in South Korea. Screening measurements from 2004–2005 served as the baseline; later records were used to track new dementia diagnoses through 2019. This design let researchers examine associations across many years, but it was observational: participants were not assigned treatments or changes in hemoglobin.
Low hemoglobin is commonly associated with anemia. Higher-than-usual levels can be associated with factors such as smoking, dehydration, lung or heart disease, or other medical conditions. Those possibilities matter when interpreting the findings: hemoglobin may reflect broader health or other influences rather than directly affect dementia risk. The researchers also noted that early, undiagnosed dementia could affect nutrition, frailty, weight, or anemia, potentially contributing to the association.
“The findings do not show that hemoglobin itself causes dementia, but suggest that abnormal hemoglobin levels may be a visible marker of wider physical vulnerability relevant to brain health.”
— Dr. Hyun Soo Kim, lead researcher and assistant professor at Dong-A University College of Medicine
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Limits of the Risk Association
The study cannot establish that hemoglobin itself causes dementia. Because it relied on records rather than a controlled intervention, other health conditions or social and medical factors could help explain the observed differences. The researchers also raised the possibility that early dementia-related changes could affect nutrition, frailty, weight loss, or anemia before diagnosis.
It is not clear whether the associations would be similar in populations with different backgrounds, health systems, or demographics. The study does not establish why the relationship appeared clearer in women, what hemoglobin ranges might be most relevant to an individual’s risk, or whether changing levels would alter dementia outcomes. Its percentages compare study groups; they are not a personal forecast.
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Further Research Across Populations
Researchers will need to test whether the association is present in people from a wider range of backgrounds and investigate what may account for the different patterns by dementia type and sex. Further studies would also need to determine whether hemoglobin adds useful information beyond other health measures and whether any intervention changes dementia outcomes.
For now, the study supports further research rather than a change to routine care. Kim advised that people discuss abnormal hemoglobin results with a doctor because they may reflect underlying health issues. The report does not recommend taking supplements or otherwise altering hemoglobin to prevent dementia.
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Key Questions
Does low hemoglobin cause dementia?
The study does not show causation. It found an association between hemoglobin groups and later dementia diagnoses, but its observational design cannot establish that low hemoglobin causes dementia.
What did the study find about high hemoglobin?
People in the highest hemoglobin fifth had a 7% higher risk of all-cause dementia than the reference group. For vascular dementia, the highest fifth had an 18% higher risk. The pattern differed by dementia type and was not consistent across all five groups.
Should people take iron to reduce dementia risk?
No such recommendation follows from this study. Lead researcher Dr. Hyun Soo Kim said the findings should not be treated as advice to take iron or to raise or lower hemoglobin to prevent dementia. People with an abnormal result can discuss it with a doctor.
How long were participants followed?
The researchers tracked new diagnoses in national health insurance records from the 2004–2005 screening period through the end of 2019, providing up to 15 years of follow-up.
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