A large 3-year study of over 2,000 healthy European adults aged 70 and older found that those with higher hemoglobin levels (a measure of iron in blood) were less likely to develop mild cognitive problems. People with hemoglobin levels above 130 g/L had 34-44% lower odds of experiencing memory and thinking difficulties compared to those with the lowest levels. While this doesn’t prove that iron prevents cognitive decline, it suggests that maintaining healthy blood iron levels might be important for brain health as we age.

The Quick Take

  • What they studied: Whether people with higher levels of hemoglobin (iron-carrying protein in blood) were less likely to develop mild memory and thinking problems over 3 years
  • Who participated: 2,150 generally healthy European adults aged 70 and older living independently in their communities, with about 62% being women
  • Key finding: People with higher hemoglobin levels had 34-44% lower odds of developing mild cognitive problems compared to those with the lowest levels
  • What it means for you: Maintaining healthy iron levels through diet or supplements (with doctor guidance) might help protect your thinking abilities as you age, though more research is needed to confirm this

The Research Details

This was part of a larger clinical trial called DO-HEALTH that followed over 2,000 healthy older adults for three years. Researchers measured participants’ hemoglobin levels (which indicates how much iron is in their blood) at the start of the study, then tested their thinking and memory skills every year using a standard test called the Montreal Cognitive Assessment (MoCA). They divided participants into five groups based on their hemoglobin levels and compared how often each group developed mild cognitive problems.

This approach is valuable because it followed the same people over time rather than just taking a snapshot, which helps researchers better understand whether low iron levels might actually contribute to cognitive decline. The large size and long follow-up period make the results more reliable than smaller, shorter studies.

This study has several strengths: it included over 2,000 people, followed them for three years, used standardized cognitive tests, and carefully controlled for other factors that might affect brain health like age, medical conditions, and lifestyle habits. However, it only included European adults, so results may not apply to all populations.

What the Results Show

The study found a clear pattern: people with higher hemoglobin levels were consistently less likely to develop mild cognitive impairment. Compared to those in the lowest group (bottom 20%), people in all higher groups had significantly better odds of maintaining their thinking abilities. The second-lowest group had 34% lower odds of cognitive problems, while the middle groups had 39-44% lower odds. Even the highest group still had 36% lower odds, suggesting there may be an optimal range rather than ‘higher is always better.’

Interestingly, when researchers looked specifically at people who met the clinical definition of anemia (very low hemoglobin), they didn’t find a significant association with cognitive problems. This suggests that the relationship between iron and brain health might be more nuanced than simply having anemia versus not having it.

Previous studies have mostly looked at this question at single points in time rather than following people over years. This study’s findings align with earlier research suggesting a connection between iron levels and brain health, but provides stronger evidence because it tracked the same people over time.

The study cannot prove that low hemoglobin causes cognitive decline - it only shows an association. The participants were all generally healthy Europeans, so results might not apply to people with chronic diseases or other ethnic groups. Also, the researchers only measured hemoglobin at the beginning, so they couldn’t track how changes in iron levels over time might affect cognition.

The Bottom Line

If you’re over 70, consider discussing your iron levels with your doctor, especially if you have concerns about memory or thinking. Maintaining adequate iron through iron-rich foods like lean meats, beans, and leafy greens may be beneficial. However, don’t start iron supplements without medical guidance, as too much iron can be harmful.

This research is most relevant for healthy adults over 70, particularly those with low-normal iron levels. People with existing cognitive problems, chronic diseases, or those already taking iron supplements should consult their healthcare provider before making changes.

The study tracked people for three years, suggesting that the relationship between iron levels and cognitive health develops over time. If you optimize your iron levels, cognitive benefits (if any) would likely take months to years to become apparent.

Want to Apply This Research?

  • Track your daily intake of iron-rich foods like red meat, poultry, fish, beans, lentils, and fortified cereals, aiming for the recommended daily amount (8mg for men over 50, 8mg for women over 50)
  • Log meals containing iron-rich foods and note any cognitive symptoms like memory lapses or difficulty concentrating to discuss patterns with your healthcare provider
  • Request hemoglobin levels be checked during annual physical exams and track these values over time, along with any changes in cognitive function or energy levels

This research shows an association but does not prove that hemoglobin levels directly cause changes in cognitive function. Do not start iron supplements without consulting your healthcare provider, as excess iron can be harmful. Individual results may vary, and this study included only generally healthy European adults over 70.