A large study tracking more than 316,000 adults for up to 15 years suggests that a routine blood test may reveal important clues about future dementia risk.
A standard blood test taken during a routine health check could offer 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 levels of hemoglobin were more likely to develop dementia, although the risks varied depending on the type of disease.
Hemoglobin is the oxygen-carrying protein in red blood cells. Low levels are commonly associated with anemia, while unusually high levels can result from smoking, dehydration, or certain heart and lung conditions. The findings suggest that this familiar blood measurement may also reflect broader aspects of physical health associated with brain aging.
Tracking Dementia Risk for Up to 15 Years
Researchers analyzed health records from 316,542 Korean adults aged 40 and older who underwent national health screenings 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 with the group that had the lowest dementia rate, 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% greater risk.
The findings, 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 and Vascular Dementia Show Different Patterns
For Alzheimer’s disease, the increased risk was concentrated among 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 pattern across all five hemoglobin groups. The researchers also observed clearer and more consistent relationships among women than men.
What Hemoglobin Levels May 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 results do not establish a direct causal relationship.
“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.”
Kim added, “Dementia is one of the fastest-growing health challenges in aging societies, and there are not many treatments and no cure. Identifying simple, accessible markers of future risk could help researchers and clinicians better understand how whole-body health relates to brain health over time.”
Could Routine Blood Tests Help Identify Future Risk?
Hemoglobin is already measured in standard blood tests around the world, making it considerably more accessible than specialized brain imaging or newer dementia biomarkers. The researchers suggest that existing blood test results could potentially help scientists investigate connections between general physical health and long-term cognitive decline.
Kim explained, “A blood test most people already get at a routine check-up may say something about their brain health many years later. In this large Korean cohort, people with unusually low hemoglobin, and, to a smaller degree, those with unusually high hemoglobin, 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 carry oxygen, matters for long-term brain health.”
Why the Findings Do Not Prove Cause and Effect
Because the study was 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 might also affect nutrition, body weight, frailty, or anemia before the disease is formally diagnosed.
“We want to emphasize that the findings should not be interpreted as advice to take iron supplements, to raise hemoglobin levels, or to lower high hemoglobin levels in order to prevent dementia. An abnormal hemoglobin result should instead be discussed with a doctor, because it may point to underlying health issues that deserve attention,” Kim said.
More Research Is Needed Across Different Populations
The study drew on health records from South Korea, leaving questions about whether the same relationships apply to people from other ethnic, geographic, and medical backgrounds. Further research is also needed to establish whether identifying abnormal hemoglobin levels can meaningfully improve dementia risk assessment or prevention.
Dr. Lindsey Sinclair (University of Southampton), who was not involved in the research, commented:
“There is a growing body of evidence that physical health and brain health are intertwined. We are also increasingly aware that changes supporting better brain health, be they medical or lifestyle changes, are important in mid-life to reduce the risk of later dementia. While this study shows a possible link between hemoglobin levels and dementia risk, more work is required to understand if this link is present in people from a wider range of backgrounds; and what can best be done to reduce dementia risk in people with the lowest and highest levels of hemoglobin.”
Meeting: 39th ECNP Congress
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