A large study of more than 316,000 adults over a period of up to 15 years suggests that a routine blood test could reveal important clues about future dementia risk.
A standard blood test taken during a routine check-up could provide clues about dementia risk more than a decade later. In a study of more than 316,000 adults, researchers found that people with unusually low or high hemoglobin levels were more likely to develop dementia, although risks vary depending on the type of disease.
Hemoglobin is the protein that carries oxygen in red blood cells. Low levels are usually associated with anemia, while unusually high levels can result from smoking, dehydration, or certain heart and lung diseases. The findings suggest that this familiar blood measurement may also reflect broader aspects of physical health associated with brain aging.
Monitoring the risk of dementia for up to 15 years
Researchers analyzed the medical records of 316,542 Korean adults aged 40 and older who underwent national health examinations in 2004 and 2005. Participants were divided into five groups based on their hemoglobin levels, from the lowest 20% to the highest 20%. National health insurance records were then used to track new dementia diagnoses through the end of 2019.
Compared to the group with the lowest rate of dementia, participants in the lowest hemoglobin category had a 16% higher risk of developing dementia from any cause. Those in the highest category had a 7% higher risk.
The results, published in the Journal of Alzheimer’s Disease and presented at the 39th ECNP Congress in Munich, also identified differences between Alzheimer’s disease and vascular dementia.
Alzheimer’s disease and vascular dementia show different patterns
For Alzheimer’s disease, the increased risk was concentrated in people with the lowest hemoglobin levels. Participants in this group were 14% more likely to develop the disease than those in the reference group.
The relationship was different for vascular dementia (caused by reduced blood flow to the brain). People in the lowest hemoglobin category had a 19% higher risk, while those in the highest category had an 18% higher risk. However, the association did not follow a consistent trend across the five hemoglobin groups. Researchers also observed clearer and more consistent relationships among women than among men.
What hemoglobin levels can reveal about brain health
Lead researcher Dr. Hyun Soo Kim, an assistant professor at Dong-A University College of Medicine in Busan, South Korea, emphasized that the findings do not establish a direct causal relationship.
“The results do not show that hemoglobin itself causes dementia, but suggest that abnormal hemoglobin levels could be a visible marker of broader physical vulnerability linked to brain health.”
Kim added: “Dementia is one of the fastest growing health problems in aging societies, and there are not many treatments or any cures. Identifying simple, accessible markers of future risks could help researchers and clinicians better understand how whole-body health is linked to brain health over time.”
Could routine blood tests help identify future risks?
Hemoglobin is already measured in standard blood tests around the world, making it considerably more accessible than specialized brain imaging or new dementia biomarkers. The researchers suggest that results from existing blood tests could potentially help scientists study links between general physical health and long-term cognitive decline.
Kim explained: “A blood test that most people already have during a routine check-up may reveal something about their brain health several years later. In this large Korean cohort, people with unusually low hemoglobin levels, and to a lesser extent those with unusually high hemoglobin levels, were more likely to develop dementia. This does not prove that hemoglobin causes dementia, but it supports the idea that general physical health, including the body’s ability to transport oxygen, is important for long-term brain health.
Why the results don’t prove cause and effect
Because the study is observational, it cannot determine whether abnormal hemoglobin levels contribute directly to dementia. Other medical conditions could influence both hemoglobin measurements and brain health. Early dementia processes may also affect nutrition, body weight, frailty or anemia before the disease is formally diagnosed.
“We would like to emphasize that the results should not be interpreted as advice to take iron supplements, increase hemoglobin levels, or reduce high hemoglobin levels in order to prevent dementia. Rather, an abnormal hemoglobin result should be discussed with a doctor, as it may indicate underlying health problems that deserve attention,” Kim said.
Further research is needed on different populations
The study used health records from South Korea, leaving open the question of whether the same relationships apply to people of other ethnic, geographic and medical backgrounds. Further research is also needed to determine whether identifying abnormal hemoglobin levels can significantly improve the assessment or prevention of dementia risk.
Dr Lindsey Sinclair (University of Southampton), who was not involved in the research, commented:
“There is growing evidence that physical health and brain health are closely linked. We are also increasingly aware that changes to promote better brain health, whether medical or lifestyle changes, are important in midlife to reduce the risk of later dementia. While this study shows a possible link between hemoglobin levels and dementia risk, more work is needed to understand whether this link is present in people from a wider range of backgrounds; and which can be best done to reduce the risk of dementia in people with the lowest and highest levels of hemoglobin.
Meeting: 39th ECNP Congress
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