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A long-term study of 316,542 adults in South Korea found that people with the lowest hemoglobin levels had a higher rate of later dementia, while the highest levels were also associated with increased risk for some outcomes. The observational findings do not show that hemoglobin causes dementia or that changing its levels can prevent it.
A study tracking 316,542 South Korean adults found that hemoglobin levels recorded during routine health screenings were associated with dementia diagnoses over as many as 15 years. People in the lowest hemoglobin group had a higher risk of all-cause dementia than the study’s reference group, while the highest group also showed a smaller increase; the research does not establish that hemoglobin causes dementia.
The researchers studied adults aged 40 and older who received national health screenings in 2004–2005. They grouped participants into five categories based on hemoglobin levels and used national health insurance records to identify new dementia diagnoses through the end of 2019. Hemoglobin is a protein in red blood cells that carries oxygen around the body.
Compared with the group that had the lowest dementia rate, participants in the lowest 20% for hemoglobin had a 16% higher risk of all-cause dementia. Those in the highest 20% had a 7% higher risk. These figures describe relative differences between groups in this study; they do not give an individual’s absolute likelihood of developing dementia.
The pattern varied by diagnosis. For Alzheimer’s disease, the higher risk was mainly seen in the lowest hemoglobin group, which had a 14% increase relative to 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 pattern did not rise or fall in a simple sequence across all five groups. The association was clearer and more consistent among women than men.
Routine Results May Aid Risk Research
Hemoglobin is already measured in standard blood tests, making it an accessible measure for researchers to study alongside other health information. If further research confirms the association across different populations, existing medical records could help investigators examine how overall physical health relates to later brain health, without relying only on specialist tests.
The result does not mean that a routine blood count can currently predict whether a particular person will develop dementia. Nor does it establish a prevention strategy. The study identifies a population-level association, not a diagnostic test or a basis for treating hemoglobin levels to reduce dementia risk.
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How Researchers Tracked Dementia
The study began with health-screening data collected in 2004–2005 and linked it to national insurance records through 2019. That long follow-up allowed the team to compare baseline hemoglobin categories with later recorded diagnoses, but the analysis remains observational: researchers measured patterns in existing data rather than assigning people to change their hemoglobin levels.
Low hemoglobin is commonly associated with anemia. Unusually high levels can be associated with smoking, dehydration, lung or heart disease, or other conditions, according to the report. These possible links make it difficult to interpret hemoglobin as an isolated factor: levels may reflect broader health circumstances that also relate to dementia risk.
The findings were presented at the 39th ECNP Congress in Munich and published in the Journal of Alzheimer’s Disease. Lead researcher Dr Hyun Soo Kim is an assistant professor at Dong-A University College of Medicine in Busan, South Korea. Dr Lindsey Sinclair of the University of Southampton commented on the work; she was not identified as a study author in the source report.
“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
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Cause, Prediction and Generalizability
Because this was an observational study, it cannot show whether low or high hemoglobin contributes to dementia, reflects other health conditions, or is related to factors not accounted for in the analysis. The researchers also noted that early, undiagnosed dementia could affect nutrition, frailty, weight loss or anemia, potentially influencing the association.
The findings come from a large Korean cohort, but the source report says it is not yet known whether the same patterns apply to people from a wider range of backgrounds. The report also does not provide enough information to determine whether hemoglobin would improve existing approaches to estimating an individual’s dementia risk, or what the absolute risk was for each group. The reasons for the differences by sex and dementia type also remain unclear.
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Further Studies Must Test the Link
Researchers will need to examine whether the findings hold in populations with different backgrounds and health profiles, and investigate what may account for the patterns across hemoglobin groups. Further work would also be needed to establish whether hemoglobin adds useful information to risk assessment and whether any intervention changes dementia outcomes.
For now, the study’s authors say an abnormal hemoglobin result should be discussed with a doctor because it may point to an underlying health issue. They specifically caution against using iron supplements or trying to raise or lower hemoglobin as a way to prevent dementia.
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Key Questions
Does low hemoglobin cause dementia?
The study does not show that it does. Its observational design found an association between hemoglobin categories and later diagnoses but cannot establish cause and effect.
What did the study find about high hemoglobin?
The highest 20% had a 7% higher risk of all-cause dementia than the reference group. For vascular dementia, the highest group had an 18% higher risk; the report describes different patterns for different dementia types.
Can a routine blood test predict an individual’s dementia risk?
Not on the basis of this study. It compared groups in a population and does not establish hemoglobin as a validated individual prediction or diagnostic test.
Should people change their hemoglobin levels to prevent dementia?
No prevention benefit was established. The study’s lead researcher cautioned against taking iron or trying to raise or lower hemoglobin for dementia prevention, and said abnormal results should be discussed with a doctor.
Source: rss
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