Type of research; peer-reviewed/observational study/people
Munich, Germany: A common blood test already carried out during routine health checks may contain clues about a person's long-term risk of dementia, according to research being presented at the ECNP Congress in Munich and recently published in the Journal of Alzheimer's Disease.
The study followed 316,542 Korean adults aged 40 and over who had a national health screening in 2004–2005, then used national health insurance records to track new dementia diagnoses until the end of 2019 — up to 15 years later. The researchers categorized the participants into 5 groups, from the 20% with the lowest haemoglobin levels, through to the 20% with the highest haemoglobin levels. Researchers found that people in the lowest 20% of haemoglobin levels had a 16% higher risk of all-cause dementia than those in the group with the lowest dementia rate, while those in the highest 20% had a 7% higher risk.
The pattern differed by dementia type. For Alzheimer's disease, the increased risk was mainly seen amongst the 20% of people with the lowest haemoglobin levels, who had a 14% higher risk than the reference group. For vascular dementia (caused by reduced blood flow to the brain), the 20% with lowest haemoglobin levels had a 19% higher risk, whereas the 20% with the highest haemoglobin levels had an 18% greater risk of developing dementia. For vascular dementia, however, the relationship did not follow a simple pattern across all five haemoglobin groups. The association was also clearer and more consistent in women than in men.
Haemoglobin is the protein in red blood cells that carries oxygen around the body. Low haemoglobin is commonly associated with anaemia, while unusually high haemoglobin may reflect factors such as smoking, dehydration, lung or heart disease, or other medical conditions.
Presenting the work at the 39th ECNP Congress in Munich, lead researcher Dr Hyun Soo Kim, assistant professor at Dong-A University College of Medicine, Busan, South Korea said:
"The findings do not show that haemoglobin itself causes dementia, but suggest that abnormal haemoglobin levels may be a visible marker of wider physical vulnerability relevant to brain health".
He continued "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".
The study is notable because haemoglobin is already measured in standard blood tests around the world. Unlike specialist scans or emerging biomarkers, it is inexpensive, familiar to doctors and patients, and often already available in routine medical records.
Dr Kim added, "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 haemoglobin — and, to a smaller degree, those with unusually high haemoglobin — were more likely to develop dementia. This does not prove that haemoglobin 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".
The researchers stress that this was an observational study and so comes with several caveats. It can identify associations, but it cannot prove that low or high haemoglobin directly causes dementia. Early, undiagnosed dementia processes may also affect nutrition, frailty, weight loss, or anaemia, which could contribute to the observed relationship.
Dr Kim said "We want to emphasise that the findings should not be interpreted as advice to take iron supplements, to raise haemoglobin levels, or to lower high haemoglobin levels in order to prevent dementia. An abnormal haemoglobin result should instead be discussed with a doctor, because it may point to underlying health issues that deserve attention".
Commenting, Dr Lindsey Sinclair (University of Southampton) said:
"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. Whilst this study shows a possible link between haemoglobin 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 haemoglobin".
Dr Sinclair was not involved in this work; this is an independent comment.
