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A study tracking 316,542 adults in South Korea found that people with very low hemoglobin levels, and to a lesser extent those with very high levels, were more likely to receive a dementia diagnosis over as many as 15 years. The observational findings do not show that hemoglobin causes dementia or that changing its level would prevent it.
A study of 316,542 South Korean adults found that people with unusually low hemoglobin levels—and, for some dementia outcomes, unusually high levels—were more likely to be diagnosed with dementia during follow-up of up to 15 years. The findings, presented at the 39th ECNP Congress and published in the Journal of Alzheimer’s Disease, suggest a possible long-term association involving a measurement already included in many routine blood tests, but do not establish that hemoglobin causes dementia.
Researchers examined adults aged 40 and older who underwent a national health screening in 2004–2005. They grouped participants into five categories according to their hemoglobin levels, then used national health insurance records to identify new dementia diagnoses through the end of 2019. Hemoglobin is the 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 fifth of hemoglobin levels had a 16% higher risk of all-cause dementia. Those in the highest fifth had a 7% higher risk. The pattern differed by diagnosis: the lowest-hemoglobin group had a 14% higher risk of Alzheimer’s disease, while for vascular dementia the lowest and highest groups had risks 19% and 18% higher, respectively. The vascular dementia association did not follow a simple pattern across all five groups.
The researchers also reported that the association was clearer and more consistent in women than in men. The figures describe relative differences in risk within this study; they do not give an individual’s likelihood of developing dementia. The report did not establish that raising or lowering hemoglobin would change that likelihood.
What Routine Hemoglobin Results Could Signal
Hemoglobin is measured in standard blood tests, so a relationship with later dementia could give researchers a way to study how general physical health and brain health are connected over time. The test is already familiar and widely used, unlike specialist scans or newer biomarkers. That makes the finding relevant to research into accessible indicators that might help identify patterns of long-term health risk.
But the study does not show that a hemoglobin result can predict dementia reliably for an individual, nor that screening or treatment based on this association prevents the condition. Low levels can be associated with anemia; unusually high levels can have several possible explanations, including smoking, dehydration, or heart and lung conditions. An abnormal result calls for medical interpretation in its own right, not a dementia conclusion.
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How Researchers Tracked Dementia Diagnoses
The study used health-screening information from a large national cohort in South Korea and linked it to insurance records for later diagnoses. Participants were followed for up to 15 years, giving researchers a way to examine whether a single earlier measurement was associated with diagnoses recorded later. The study was observational: it compared outcomes among people with different hemoglobin levels rather than assigning levels or treatments.
Lead researcher Dr. Hyun Soo Kim, an assistant professor at Dong-A University College of Medicine, said the findings do not show that hemoglobin itself causes dementia. He described abnormal levels as a possible visible marker of broader physical vulnerability relevant to brain health. The research was presented at the ECNP Congress in Munich and published in the Journal of Alzheimer’s Disease.
Cause, Prediction and Wider Applicability
Because the research was observational, it cannot determine whether hemoglobin levels contribute to dementia, reflect other health conditions, or are associated with dementia for another reason. The researchers noted that early, undiagnosed dementia could affect nutrition, frailty, weight, or anemia, potentially influencing the relationship seen in the data.
The report also does not establish how useful hemoglobin would be as a prediction tool for an individual, or whether the results apply to populations with different backgrounds. The reasons for the differences by dementia type and the stronger, more consistent association in women are not settled by the findings. The reported risk differences should not be treated as a diagnosis or personal forecast.
Further Studies Needed Beyond Korea
Researchers will need to test whether the association appears in populations with a wider range of backgrounds and to clarify how hemoglobin relates to dementia risk over time. Further work would also need to distinguish whether abnormal levels are a marker of other health problems or play a role in pathways connected to brain health.
For now, the study authors caution against using the result to guide supplements or attempts to alter hemoglobin for dementia prevention. People with an abnormal result should discuss it with a qualified health professional, who can assess possible causes and appropriate care. The study does not report a specific date for additional results or a clinical screening recommendation.
Key Questions
Does low hemoglobin cause dementia?
The study does not show that it does. It found an association between hemoglobin levels and later diagnoses, but its observational design cannot establish cause and effect.
What did the study find about high hemoglobin?
Participants in the highest 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 across all five groups was not simple.
Should I take iron to reduce dementia risk?
No prevention benefit was tested, and the lead researcher specifically cautioned against interpreting the findings as advice to take iron or alter hemoglobin levels. Discuss abnormal blood-test results with a qualified health professional.
How long were participants followed?
The 316,542 adults had health screenings in 2004–2005; national insurance records were used to track new diagnoses through the end of 2019, for up to 15 years.
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