A new study has found that the effects of anemia—a condition caused by a lack of hemoglobin needed to carry oxygen to organs and tissues—may stretch beyond fatigue, shortness of breath, and pale skin. They reach into the brain, raising the risk of dementia and linking to higher levels of biomarkers associated with Alzheimer’s disease (AD) and neurodegeneration.
Researchers from Sweden and Italy set up a long-term study tracking 2,282 dementia-free adults aged 60 and above who live in Stockholm, Sweden. At the start of the study, the team measured hemoglobin levels and biomarkers associated with neurodegenerative disorders in all participants. Over the years, the team followed up with the group, checking in every 3 to 6 years to see how their health evolved.
When researchers dug into more than ten years of data, they found that people who had anemia at the start were 66% more likely to develop dementia over time. Within the follow-up of 9.3 years, 362 participants had developed dementia. The numbers also pointed to a strong link between low hemoglobin and higher levels of blood biomarkers tied to Alzheimer’s disease, including proteins linked to brain cell damage and inflammation. This association was stronger in men than in women.
The findings are published in JAMA Network Open.
Decoding data to spot the link
Anemia affects around one in ten people over the age of 65 and has been linked to a range of poor health outcomes, including a higher risk of dementia. One leading explanation is reduced oxygen delivery to the brain over time, which can place sustained stress on brain cells, damage blood vessels, and gradually lead to the loss of neurons. This is supported by imaging studies that show brain shrinkage and signs of tissue damage in individuals with anemia.
Earlier research has also reported elevated levels of Alzheimer’s-related biomarkers in the blood of people with anemia. However, it was not clear whether these changes directly reflected underlying brain damage. Further investigation into this relationship could provide clues as to how anemia could influence the development and progression of dementia.
In this study, the researchers put to use the data from the Swedish National Study on Aging and Care in Kungsholmen (SNAC-K)—a long-running, population-based study designed specifically to track how people age—to understand the links between anemia and AD (which includes dementia) pathology.
The results indicated that anemia is strongly linked to a higher risk of dementia and early warning signs of brain damage in older adults. The risk was highest in individuals who had both anemia and elevated levels of three key warning proteins in the blood: Phosphorylated tau 217 (p-tau217), a biomarker that builds up in the brain during Alzheimer’s-related changes; Neurofilament light chain (NfL), a marker of nerve cell damage; and Glial fibrillary acidic protein (GFAP), a signal of stress or inflammation in cells. For instance, people with both anemia and high NfL had a 3.5-fold higher risk of developing dementia.
These findings could mean that anemia makes the brain more vulnerable, so signs of dementia show up sooner or with less underlying damage than usual.
Researchers suggest that anemia may be a clinically important factor in assessing dementia risk and could be used as a potentially modifiable risk factor for preventing AD. Further long-term studies are required to see whether screening for anemia and treating the condition can help prevent cognitive decline.