A common blood measure taken at routine health checks, hemoglobin, may carry a signal about a person's risk of developing dementia years later. Researchers presenting work at the ECNP Congress in Munich, and published in the Journal of Alzheimer's Disease, followed 316,542 Korean adults aged 40 and over who had a national health screening in 2004 and 2005. Using national health insurance records, they tracked new dementia diagnoses until the end of 2019, up to 15 years later.
Participants were sorted into five groups, from the 20% with the lowest hemoglobin levels to the 20% with the highest. People in the lowest group had a 16% higher risk of all-cause dementia than those in the reference group with the lowest dementia rate. The highest group had a 7% higher risk. The pattern shifted by dementia type. For Alzheimer's disease, the increased risk appeared mainly in the lowest hemoglobin group, at 14% higher. For vascular dementia, caused by reduced blood flow to the brain, both the lowest group (19% higher) and the highest group (18% higher) showed elevated risk, though the relationship did not follow a simple pattern across all five groups. The association was also clearer and more consistent in women than in men.
Hemoglobin is the protein in red blood cells that carries oxygen around the body. Low levels are commonly linked to anemia, while unusually high levels may reflect factors such as smoking, dehydration, lung or heart disease, or other conditions. Lead researcher Dr Hyun Soo Kim, of Dong-A University College of Medicine in Busan, South Korea, said the findings do not show that hemoglobin itself causes dementia, but suggest abnormal levels may be a visible marker of wider physical vulnerability relevant to brain health.
The appeal of the work lies in the test itself. Hemoglobin is already measured in standard blood tests worldwide, so it is inexpensive, familiar to doctors and patients, and often already sitting in medical records. Dr Kim described dementia as one of the fastest-growing health challenges in aging societies, with few treatments and no cure, which makes simple, accessible markers of future risk worth examining.
The researchers stress that this was an observational study. It can identify associations but cannot prove that low or high hemoglobin directly causes dementia. Early, undiagnosed dementia processes may themselves affect nutrition, frailty, weight loss, or anemia, which could contribute to the observed link. Dr Kim also said the findings should not be read as a case for iron supplements or for adjusting hemoglobin levels to prevent dementia, and that an abnormal result should be discussed with a doctor because it may point to underlying health issues. Whether the link holds in people from more varied backgrounds remains an open question.