Researchers followed 530 older adults in Taiwan for 8 years to see if the size of their red blood cells affected their thinking and memory skills. They found that people with larger red blood cells at the start of the study had more trouble with memory and attention as they got older. This connection was especially strong in men and in people with high platelet counts or high hemoglobin levels. While this is interesting, scientists say we need more research to fully understand why this happens and what we should do about it.

The Quick Take

  • What they studied: Whether the size of red blood cells (measured as MCV) is connected to memory, attention, and thinking problems in older people over time
  • Who participated: 530 healthy older adults living in Taiwan, average age 73 years old, with about half men and half women. None of them had dementia at the start of the study
  • Key finding: People with larger red blood cells at the beginning had noticeably worse memory and attention scores over the 8-year period, especially those with high platelet counts or high hemoglobin levels
  • What it means for you: If you’re an older adult, your doctor might want to check your red blood cell size as part of routine blood work. However, this is early research, and having larger red blood cells doesn’t mean you will definitely have memory problems. Talk to your doctor about what your blood work means for your health

The Research Details

This was a long-term follow-up study that started in 2011 and continued through 2022. Researchers recruited 530 older adults who didn’t have dementia and checked on them every two years for 8 years total. At the beginning and during each follow-up visit, they measured the size of the participants’ red blood cells and tested their memory, attention, and thinking skills using standard tests. They also measured other blood markers like hemoglobin (the protein that carries oxygen) and platelets (cells that help with blood clotting).

The researchers used special statistical methods to look at whether larger red blood cells were connected to worse thinking and memory scores over time. They adjusted their analysis to account for other factors that might affect cognition, like age, sex, education, and health conditions.

This type of study is valuable because it follows the same people over many years, which helps show whether changes in red blood cell size happen before thinking problems develop.

Understanding what happens in the blood before memory problems start could help doctors catch cognitive decline early. Red blood cells carry oxygen to the brain, so their size and function might be important for brain health. This research suggests that simple blood tests might help identify older adults at risk for memory problems

This study has several strengths: it followed people for a long time (8 years), tested memory and thinking in multiple ways, and included a decent-sized group of participants. However, all participants were from Taiwan, so results might not apply to other populations. The study also couldn’t prove that larger red blood cells actually cause memory problems—only that they’re connected. Other factors not measured in the study could explain the connection

What the Results Show

The main finding was that people with larger red blood cells (bigger than 93.0 fL, which is a tiny unit of measurement) had worse memory scores over the 8 years compared to those with smaller red blood cells. This was true for three types of memory tested: remembering things right away, remembering them after a delay, and remembering the main idea of something they learned.

People with larger red blood cells also had worse attention skills, measured by how many numbers they could repeat back in order. The connection between red blood cell size and poor memory was especially strong in men and in people who had high platelet counts or high hemoglobin levels at the start of the study.

Interestingly, the relationship between red blood cell size and overall thinking ability changed depending on age. This suggests that age might play a role in how red blood cell size affects the brain.

The study found that the connection between red blood cell size and cognition wasn’t simple—it wasn’t just that bigger is always worse. Instead, there was a specific range where problems appeared. The researchers also noticed that people with certain combinations of blood markers (like high platelets plus large red blood cells) seemed to have more cognitive problems, suggesting that multiple blood factors might work together to affect brain health

Previous research suggested that larger red blood cells might mean the brain isn’t getting enough oxygen and nutrients, but most of that research was short-term or didn’t follow people over time. This 8-year study provides stronger evidence that this connection might be real and long-lasting. However, the researchers note that we still don’t have enough studies like this one to be completely sure about the relationship

The study only included older adults from Taiwan, so we don’t know if these findings apply to other countries or ethnic groups. All participants were living in the community and didn’t have dementia at the start, so results might be different for people with dementia or those in nursing homes. The study couldn’t prove that larger red blood cells actually cause memory problems—only that they’re connected. Other unmeasured factors could explain the relationship. Additionally, vitamin B12 levels were collected but not fully analyzed, which is important because B12 affects both red blood cell size and brain function

The Bottom Line

If you’re an older adult, ask your doctor to check your red blood cell size as part of routine blood work. If your red blood cells are larger than normal, discuss with your doctor whether additional monitoring of your memory and thinking is appropriate. This research suggests it might be worth paying attention to, but it’s not yet clear what specific actions to take based on red blood cell size alone. (Confidence: Moderate—this is early research that needs confirmation)

This research is most relevant to older adults (65+), particularly men and those with high platelet counts or high hemoglobin. If you’re younger or don’t have these risk factors, this research is less directly applicable to you right now. Anyone with a family history of memory problems or dementia might want to discuss this with their doctor

Memory and attention changes related to red blood cell size appear to develop gradually over years, not weeks or months. If you make changes based on this research, you should expect to see any benefits over a period of months to years, not immediately

Want to Apply This Research?

  • Track your blood test results quarterly or semi-annually, specifically noting your MCV (mean corpuscular volume) value. Record it alongside memory or attention observations (like whether you’ve noticed any changes in remembering appointments or focusing on tasks)
  • Use the app to set reminders for annual or biennial blood work that includes a complete blood count (which measures red blood cell size). Create a simple log to note any memory or attention changes you notice, then compare these observations to your blood test results over time
  • Establish a baseline by recording your current MCV value and cognitive function (using simple self-assessments like remembering a shopping list or focusing on a task). Then track these measurements annually alongside other health markers like hemoglobin and platelet counts to see if patterns emerge over time

This research suggests an association between red blood cell size and memory problems in older adults, but it does not prove that one causes the other. These findings are from a single study conducted in Taiwan and may not apply to all populations. This information is for educational purposes only and should not replace professional medical advice. If you’re concerned about memory changes or cognitive decline, please consult with your healthcare provider. Do not make changes to your medical care based solely on this research without discussing it with your doctor first. Your doctor can interpret your individual blood work results and recommend appropriate monitoring or treatment based on your specific health situation.