Yep, the brain fog thing is a real perimenopause complaint. Researchers have found some small changes in things like memory, attention and processing speed, but there’s more going on than hormones alone. Bad sleep, stress, anxiety and hot flashes can all make you feel foggier too. The reassuring part is that these changes are usually mild and aren’t the same thing as dementia. So forgetting why you walked into a room? Annoying, but you’re definitely not the only one doing it.
You walk into the kitchen and forget why you’re there. You lose your phone while you’re holding it. A word you’ve used approximately 10,000 times disappears right when you need it.
Then comes the slightly unnerving thought: Why am I suddenly so forgetful?
If you’re somewhere in your 40s or 50s, perimenopause could be part of the answer.
Women have been describing “brain fog” during the menopause transition for years, and researchers are finding evidence that some aspects of cognitive function shift during this period. But the story is more complicated, and more reassuring, than “menopause makes you lose your memory.”
Brain Fog Isn’t Just Forgetfulness
“Brain fog” isn’t a medical diagnosis. It’s a convenient name for a collection of frustrating cognitive problems.
Forgetting why you walked into a room fits. So does struggling to retrieve a word, losing your train of thought, having trouble concentrating or feeling like it takes more effort to juggle several things at once.
A 2023 review of perimenopause research found the strongest evidence for changes involving verbal learning and verbal memory. Researchers also found evidence suggesting processing speed, attention and working memory could be affected.
More recent research has continued trying to figure out exactly what is happening and, importantly, whether the brain fog women experience in everyday life shows up on cognitive tests.
Researchers Are Finding Something Interesting
A 2026 systematic review and meta-analysis pulled together 26 studies involving 9,428 participants.
Overall, perimenopausal women had poorer cognitive outcomes than premenopausal women, although the findings varied considerably depending on how researchers defined and measured perimenopause. The authors specifically noted the importance of using standardized criteria when studying these changes.
Then another large 2026 study looked at more than 14,000 women between 45 and 55.
Women in perimenopause were more likely than premenopausal women to report cognitive symptoms. But when researchers tested their cognitive performance, the differences between menopause groups were minimal.
Which raises an interesting question.
How can your brain feel so foggy when a cognitive test says you’re doing fine?
A Memory Test Isn’t the Same as Tuesday Morning
Imagine sitting somewhere quiet and being asked to complete a memory test.
Now compare that with trying to remember the name of your kid’s orthodontist while making breakfast, answering an email, looking for someone’s missing sneaker and realizing you forgot to put the laundry in the dryer yesterday.
Those aren’t exactly the same cognitive environment.
A 2025 systematic review and meta-analysis examined 24 studies involving 5,629 women to see how women’s reports of cognitive problems compared with objective cognitive testing.
The connection was surprisingly weak.
Researchers found a small association with one measure involving learning efficiency, but associations across other cognitive areas weren’t statistically significant.
That doesn’t mean women are imagining brain fog. Researchers are increasingly questioning whether traditional cognitive tests adequately capture the fluctuating, everyday problems women describe.
In other words, science is still figuring out how to measure the experience.
Hormones Probably Aren’t Working Alone
It’s tempting to blame estrogen for everything happening in your 40s.
The reality is messier.
Hormonal changes are one possible part of what’s happening in the brain during the menopause transition. But researchers have also found associations between cognitive difficulties and other common perimenopause experiences, including poor sleep, depression and hot flashes.
And then there’s regular life.
Stress affects concentration. Poor sleep affects memory. Anxiety makes it harder to focus. Trying to keep track of 47 things simultaneously isn’t particularly helpful either.
That makes it difficult to separate the direct effects of hormonal changes from everything happening alongside them.
There probably isn’t one single explanation for perimenopause brain fog.
The Reassuring Part
Forgetfulness during perimenopause does not automatically mean something is seriously wrong with your brain.
Researchers studying menopause-related brain fog describe these cognitive changes as generally mild and variable. They are also considered distinct from the progressive cognitive decline associated with dementia.
There’s considerable variation between women, too. Some experience noticeable cognitive difficulties. Others don’t. Even among women who do, the particular problems aren’t always the same.
That doesn’t mean every memory problem in your 40s should automatically be blamed on hormones.
Memory changes that are severe, worsening, interfering substantially with everyday life or concerning you deserve a conversation with a healthcare provider. There are plenty of other things that affect cognition and memory.
But occasionally standing in the laundry room wondering what on earth you came in there for?
You have plenty of company.
And researchers are finally paying closer attention to why.
