Does low iron cause brain fog?

A new study looks at possible links between iron deficiency and brain fog in perimenopause

One of my long-time patients turns 50 this year, so when I saw her recently I asked about perimenopause symptoms. She noted that her thinking wasn’t as sharp as it had been. As a successful lawyer, she had felt embarrassed at work a few times when she lost a train of thought mid-sentence or couldn’t think of a specific word.

Cognitive changes in perimenopause are well described. We have talked about them before. Studies performed in a subset of participants in the Study of Women’s Health Across the Nation (SWAN) showed that women in perimenopause see a decline in working memory and difficulty with word recall. They also show a decreased ability to learn, demonstrated by the fact that when participants repeated the same tests over time, scores didn’t improve as expected.

What causes cognitive change in perimenopause?

Many of my patients worry that cognitive changes in perimenopause are a sign of early dementia. Luckily, data from SWAN shows that cognitive performance rebounds after the last menstrual period, suggesting that the cognitive symptoms women experience are not just normal aging, but instead are related to the hormonal shifts of perimenopause.

Researchers have blamed cognitive changes on the sleep disruption that many perimenopausal women experience. Indeed, we know that sleep deprivation can impair cognitive function as much as being drunk can. But the SWAN investigators noted that the changes found were independent of sleep disruption. Put another way, sleep disruption might be one factor affecting women’s cognitive function, but not the only factor.

Iron levels and cognitive function

Blood iron levels have been correlated with cognitive function in teens and women of reproductive age. Women constantly lose iron due to menstrual bleeding. As a result, women are much more likely to be iron deficient than men.

Given that women in perimenopause can have heavier periods and given that cognitive symptoms seem to improve after the last menstrual period, it would make sense that low iron levels might contribute to cognitive symptoms in perimenopause. But until a new study was published this year, there was little data regarding any connection between blood iron levels and cognitive function among women during the perimenopausal transition.

One concern that comes up when experts consider the role of iron in cognition is that there is some data suggesting that iron build up in the brain may cause oxidative stress—that is, stress on a cellular level. Oxidative stress causes cells to breakdown and die. In fact, researchers think that iron build-up in the brain may be one cause of cognitive decline as people age. So, even if brain fog and other cognitive symptoms women experience in perimenopause are related to low iron in the blood, is it safe to give them iron to raise their blood iron levels? Or will all that extra iron end up in their brains where it will cause cognitive decline later? The study linked above was designed to try to answer that question.

New data seeks sort this out

The study recruited women in perimenopause who were not anemic and measured the iron in their blood. They also used magnetic resonance imaging (MRI) to measure the iron levels in their brains. Then they gave the women a series of tests. They even recorded electroencephalographic (EEG) data to measure brain activity while the women were taking the tests.

The authors found that the women who had high levels of one particular iron measure, a protein called ferritin, performed better on the tests and had more brain activity while taking the tests. This means supplementing iron could be one way to improve cognitive symptoms during perimenopause.

But does doing so come at the cost of increased iron in the brain and worsening cognitive decline later? To answer that question, we need to compare iron levels in the blood and iron levels in the brain. Based on the measurements of iron on the MRIs, the authors found no link between the women’s current iron levels in the blood and iron levels in the brain. Having higher blood levels of iron did not appear to lead to increased iron in the brain.

Don’t run out and buy an iron supplement yet!

First of all, it is not safe to take iron if you don’t need it. In addition to the brain, iron can get deposited in the liver, heart, and pancreas. As a result, excessive iron can cause liver damage, diabetes, and heart disease. You should only take iron if your doctor tests your levels and tells you that they are low.

Additionally, this study was small, including just 27 participants. And it was just a single point in time. The women with high iron levels weren’t necessarily taking iron supplements. Their levels were likely high due to their diet and how heavy or light their periods were.

Ideally, we would want more data from a study that randomized women with low iron levels to either take an iron supplement or placebo, and measured cognitive testing before and after the iron supplement was given to see if cognitive function improved. We might also like more data on how taking iron supplements, as opposed to having high iron levels, affects or does not affect iron levels in the brain.

Still, this new study gives us some important clues and ideas for future research that will improve our understanding of why women experience cognitive changes in perimenopause.

The Savvy Short

• Cognitive symptoms are common in perimenopause, but we don’t fully understand what causes them.

• Low iron levels in the blood have been associated with decreased cognitive function in girls and women during their reproductive years.

• Iron deposits in the brain are thought to be one cause of age-related cognitive decline, making some experts wary of supplementing low iron levels in middle-aged women.

• A new study found that perimenopausal women with high blood iron levels performed better on cognitive testing. It also found no correlation between brain iron levels and blood iron levels. This suggests raising iron levels might be one way to improve cognitive symptoms during perimenopause, but more data is needed to confirm.