The other day a patient came in for a follow-up visit. At her previous visit, we had initiated hormone replacement therapy to treat her perimenopausal symptoms, and I was excited to see how she was doing. She reported that her hot flushes and night sweats had practically vanished. She was sleeping better. In general, she was feeling light-years better.
“The only thing that is not great is the brain fog,” she told me. She went on to tell of difficulty finding the right words at times, struggling to think through logistically complex problems, and forgetting events. “I am worried I have early dementia,” she said, only half-joking.
Brain fog is one of the most common complaints I hear from my patients. More often than not, the current symptoms are annoying. But behind the annoyance is the fear that the forgotten name and lost keys today represent the beginning of something more serious.
What exactly is brain fog? Why does it seem to occur in midlife? Is it really the beginning of more serious cognitive decline?
What is brain fog?
In the medical literature, brain fog is defined as a constellation of cognitive symptoms that most frequently manifest in memory and attention difficulties, including difficulty understanding words and recalling words, names, stories, or numbers; difficulty maintaining train of thought; distractibility; forgetting intentions (i.e. why did I just walk into the living room?); and difficulty switching between tasks.
The Study of Women’s Health Across the Nation (SWAN) found that about 60% of women report changes in cognitive function during the menopausal transition. While brain fog is frustrating, only about 10% of women experience severe symptoms that impair their functioning. However, until relatively recently, there were very few studies in the literature regarding these changes.
Why is brain fog so prevalent in midlife?
Aging is associated with cognitive decline among women and men. Some experts have suggested that brain fog is just a manifestation of the normal aging process. Additionally, we know that estrogen acts in the brain at the cellular level. A variety of cells throughout the brain have estrogen receptors, though we don’t fully understand how estrogen is acting on those cells. Neuroscientists are only beginning to turn their attention to this question. But researchers believe that some of the cognitive changes seen during perimenopause are the direct effect of falling estrogen levels.
Researchers have also posited that hot flushes, night sweats, and sleep disruption might decrease cognitive function. While there are no studies of sleep deprivation and cognitive function in perimenopausal women specifically, there is a wealth of literature that demonstrates the connection between sleep deprivation and cognitive function in the general population.
But data collected by SWAN researchers suggests that sleep deprivation is at best only part of the picture. Participants in SWAN performed a series of cognitive tests during each of their study visits. Those tests showed that women in perimenopause experienced a decrease in memory and the speed at which they could perform mental tasks — referred to as processing speed.
However, researchers did not find an association between the severity or frequency with which the women were experiencing hot flushes and night sweats, or the degree of sleep disruption, and their performance on cognitive tests. This indicates that something else is acting in the brain. Given what we do know about estrogen in the brain, it makes sense that low estrogen levels may be the culprit.
Does brain fog lead to dementia?
I don’t want to bury the lede here — no, brain fog is not a sign of early dementia.
The SWAN investigators found that women’s cognitive test scores stagnated during perimenopause. Women repeated the same tests and did not improve their scores. They did not learn how to perform better. But they did not perform worse with time either, which is what we would expect to see if these changes were due to aging. This suggests that the cognitive changes seen in perimenopause are not normal aging. Rather, researchers describe it as a hiatus in learning.
Importantly, once the menopausal period had passed, cognitive scores rebounded, and repeating the same test did result in improved test scores. This seems to show that once our brain acclimates to the new post-menopausal hormonal milieu, brain fog resolves. Both processing speed and verbal memory improved after menopause in the SWAN participants, further supporting the idea that brain fog is not normal aging and that it is not an early sign of dementia.
Does hormone replacement improve brain fog?
Brain fog, like many other perimenopausal symptoms, will likely resolve on its own with enough time. Still, perimenopausal symptoms can last for upward of 10 years. Women in midlife have careers and busy lives. We want to feel like we can perform at our best. Naturally, we would like to treat brain fog, especially when it is impairing our functioning.
It is logical to think, given the role we believe estrogen plays in brain function, that hormone replacement therapy might improve the symptoms of brain fog. Unfortunately, there are no trials of estrogen alone or with progesterone specifically for the treatment of brain fog. There is one small study from 1988 in which estrogen was noted to improve memory in women who had their ovaries removed. There is certainly a need for more research into the effects of estrogen on cognitive function in a more broadly representative sample of women.
We do know that estrogen effectively treats hot flushes, night sweats, and sleep disruption. For most women, hormone replacement is safe. So to the degree that brain fog may be exacerbated by those symptoms, it is definitely worth considering hormone replacement. Additionally, prioritizing sleep and treating sleep issues that may be present could also be helpful.
The bottom line
- Brain fog is a common symptom among women during the perimenopausal years and includes changes in memory and processing speed.
- Brain fog is temporary. It resolves in the postmenopausal years and is not associated with risk of dementia.
- There is no evidence regarding the effectiveness of hormone replacement for cognitive symptoms in perimenopause.
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