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A 15-year observational study of 316,542 South Korean adults found that unusually low hemoglobin, and to a lesser extent unusually high hemoglobin, was associated with later dementia diagnoses. Researchers say the results 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 hemoglobin levels measured during routine health screenings were associated with the likelihood of a later dementia diagnosis over as long as 15 years. The observational research, presented at the 39th ECNP Congress in Munich and published in the Journal of Alzheimer’s Disease, does not show that hemoglobin causes dementia or that changing its level can prevent it.
The researchers examined adults aged 40 and older who had a national health screening in 2004 or 2005. They grouped participants into five equal-sized categories based on hemoglobin, a protein in red blood cells that carries oxygen. National health insurance records were used to identify new dementia diagnoses through the end of 2019.
Compared with the group that had the lowest rate of dementia, 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 associations reported by the study, not evidence that either hemoglobin level directly produced the diagnoses.
The pattern varied by dementia type. For Alzheimer’s disease, the higher risk was concentrated among people in the lowest hemoglobin group, at 14% above the reference group. For vascular dementia, the lowest group had a 19% higher risk and the highest group an 18% higher risk; the relationship did not follow a simple pattern across all five categories. The researchers also reported that associations were clearer and more consistent in women than in men.
What Routine Blood Counts Could Reveal
Hemoglobin is already measured in many standard blood tests, making it an accessible measure for researchers to study alongside long-term health records. The findings add to research into how general physical health may relate to brain health, and could help guide further investigation into factors associated with dementia risk.
But the study does not establish that hemoglobin testing can predict an individual’s future dementia, nor does it offer a prevention strategy. Lead researcher Dr. Hyun Soo Kim, an assistant professor at Dong-A University College of Medicine in Busan, said the findings may point to abnormal hemoglobin as a marker of wider physical vulnerability. A marker can be associated with an outcome without being its cause.
The distinction matters for patients. The results do not support taking iron supplements, trying to raise hemoglobin, or trying to lower it to prevent dementia. An abnormal result can have many possible explanations and should be discussed with a clinician in light of a person’s health and medical history.
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How Researchers Tracked Hemoglobin
The study began with health screenings conducted in 2004–2005 and used insurance records to track dementia diagnoses for up to 15 years. Because the analysis relied on existing measurements and later diagnoses rather than assigning an intervention, it was an observational study. It can identify patterns, but cannot determine whether hemoglobin levels caused those patterns.
Hemoglobin levels can be affected by different circumstances. Low levels are commonly associated with anemia; unusually high levels may reflect smoking, dehydration, lung or heart disease, or other medical conditions. The study’s reported associations therefore do not identify a single mechanism linking hemoglobin and dementia.
Commenting on the findings, Dr. Lindsey Sinclair of the University of Southampton said they fit with a broader interest in links between physical and brain health, while stressing the need to study people from a wider range of backgrounds and establish what, if anything, might reduce risk for people at either end of the hemoglobin range.
Limits of the Dementia Link
The study cannot show whether abnormal hemoglobin contributed to dementia, reflected other health conditions, or was associated with factors not fully accounted for. The researchers also noted that early, undiagnosed dementia processes could affect nutrition, frailty, weight loss, or anemia, which might help explain the observed relationship.
The findings come from a cohort in South Korea, so it remains unclear whether the same patterns would appear in populations with different backgrounds. The report also does not establish how useful an individual hemoglobin reading would be for predicting dementia, or whether acting on a reading changes a person’s risk.
Kim said the results should not be interpreted as advice to take iron, raise hemoglobin, or lower a high level for dementia prevention. No such intervention was tested in this study.
Research Needed Beyond This Cohort
Further studies will need to test whether the association appears in people from a wider range of backgrounds and clarify how other health conditions and possible early dementia changes affect the results. Researchers will also need to determine whether hemoglobin adds useful information to other measures of risk.
For now, the report does not announce a change to routine screening or dementia care. People with an abnormal hemoglobin result should discuss it with a qualified health professional; the study provides no basis for changing treatment or supplements to prevent dementia.
Key Questions
Does a low hemoglobin result mean someone will develop dementia?
No. The study found a group-level association between hemoglobin categories and later diagnoses. It does not predict what will happen to an individual or prove that low hemoglobin causes dementia.
What did the study find about high hemoglobin?
People in the highest fifth of hemoglobin levels had a 7% higher risk of all-cause dementia than the reference group. For vascular dementia, the highest fifth had an 18% higher risk. These findings are observational, and the vascular dementia pattern was not consistent across all five groups.
Should people take iron supplements to reduce dementia risk?
No such advice follows from this study. The researchers said the findings should not be treated as a reason to take iron or otherwise change hemoglobin levels for dementia prevention. Discuss abnormal test results with a doctor.
How long were participants followed?
The 316,542 adults had screenings in 2004–2005, and researchers used health insurance records to track new dementia diagnoses through the end of 2019—up to 15 years.
Source: rss
