Routine Blood Test May Offer Clues To Future Dementia Risk

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A study tracking 316,542 South Korean adults found that people with the lowest hemoglobin levels had a higher rate of later dementia diagnoses; the highest levels were also associated with higher risk for some outcomes. The observational findings do not show that hemoglobin causes dementia or that changing its level prevents it.

A study of 316,542 adults in South Korea found that hemoglobin levels recorded during routine health screenings were associated with dementia diagnoses made over as many as 15 years. The results, presented at the 39th ECNP Congress and published in the Journal of Alzheimer’s Disease, suggest a possible long-term risk marker, but do not show that hemoglobin levels cause dementia.

The researchers examined adults aged 40 and older who received national health screenings in 2004–2005, then used national health insurance records to identify new dementia diagnoses through the end of 2019. Participants were divided into five groups according to their hemoglobin levels, from the lowest fifth to the highest fifth. Hemoglobin is the protein in red blood cells that carries oxygen through the body.

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 increased risk was chiefly found among people in the lowest fifth, whose risk was 14% higher than the reference group.

For vascular dementia, the pattern was less straightforward: the lowest hemoglobin group had a 19% higher risk, while the highest group had an 18% higher risk. The study reported that the relationship did not follow a simple progression across all five groups. Associations were also clearer and more consistent in women than in men, according to the report.

What Routine Blood Counts Could Reveal

Hemoglobin is measured in standard blood tests, making it a familiar and relatively accessible measure compared with specialist brain scans or newer biological markers. If further research confirms the association, existing health records could help researchers study how physical health relates to brain health over time, and potentially identify groups for closer investigation.

That possibility remains separate from using the test to predict an individual person’s future. This study reports differences in risk between groups; it does not establish a reliable personal forecast, show that a hemoglobin result can diagnose dementia, or demonstrate that treating an abnormal result reduces dementia risk. The findings may matter to research into midlife health and later brain health, but they do not change clinical guidance on their own.

How the Korean Cohort Was Tracked

The study drew on a large national cohort: 316,542 Korean adults screened in 2004–2005. Researchers linked screening measurements to health insurance records to follow new diagnoses for up to 15 years. This design allowed them to examine long-term associations in a large population, but it was observational: participants were not assigned to have particular hemoglobin levels.

Low hemoglobin is commonly associated with anemia. The report notes that unusually high readings can be related to smoking, dehydration, lung or heart disease, and other medical conditions. These possible underlying factors matter because the study cannot establish that hemoglobin itself explains the later dementia diagnoses. The research was published in the Journal of Alzheimer’s Disease and presented at the ECNP Congress in Munich.

“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

Causation and Wider Applicability

The observational design can identify an association, but it cannot determine whether low or high hemoglobin contributes to dementia or reflects other health conditions that affect dementia risk. The researchers also said early, undiagnosed dementia processes could influence nutrition, frailty, weight loss, or anemia, potentially contributing to the observed relationship.

It is also unclear whether the findings apply to people from backgrounds beyond this Korean cohort. The reported patterns differed by dementia type and were not uniform across hemoglobin groups; the association was clearer in women than in men. The study does not establish a hemoglobin threshold for predicting dementia, nor does it show whether treating abnormal levels changes later risk.

Further Studies Must Test the Link

Further research will be needed to see whether the association appears in populations with different backgrounds and health profiles, and to clarify how hemoglobin levels relate to other medical and social factors. Studies would also need to determine whether any changes to care based on these findings improve outcomes; this report does not provide that evidence.

For now, the researchers advise against interpreting the results as a reason to take iron or deliberately raise or lower hemoglobin to prevent dementia. People with an abnormal result should discuss it with a doctor, as it may warrant evaluation for underlying health issues. The next step for the research is to establish whether the association is reproducible and clinically useful.

Key Questions

Does low hemoglobin cause dementia?

The study does not show causation. It found an association between hemoglobin levels and later dementia diagnoses, but other health factors or early dementia-related changes could help explain the relationship.

Did high hemoglobin also relate to dementia risk?

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, though the pattern across all five groups was not simple.

Should people change their hemoglobin levels to prevent dementia?

No. The researchers said the results are not advice to take iron or raise or lower hemoglobin as a dementia-prevention measure. Discuss an abnormal result with a doctor.

How long were participants followed?

The 316,542 adults had health screenings in 2004–2005 and were tracked for new diagnoses through the end of 2019, a period of up to 15 years.

Source: rss