Cognitive changes during perimenopause vary between women and over time, and may include brain fog, difficulty concentrating or changes in short-term memory. Brain fog is not a condition on its own, rather it is a group of symptoms together that include lack of focus, scattered thoughts, difficulty focusing, slow reaction times, and memory trouble. In addition to the effects of estrogen decline , brain fog is a symptom also associated with chronic stress, depression, burnout, dehydration, poor nutrition and some medications.  
If you are experiencing brain fog, you are not alone: more than 60% of the women in the Seattle Midlife Women’s Health across the Nation reported an undesirable change in memory. 
As well, changes in memory are strongly linked with hot flashes, insomnia and fatigue.
It is still unclear how much of these changes can be blamed on hormones versus the impacts of other menopause symptoms such as hot flashes and insomnia. To date, research does not support that depression, anxiety, sleep disturbances and vasomotor symptoms (including hot flashes) are the primary cause of these cognitive difficulties during the menopause transition.  However, it has been shown that women who have severe PMS-like symptoms are more sensitive to changing hormone levels, and may also experience worse symptoms during perimenopause.
Studies of cognition (aka “brain fog”) issues indicated that perimenopausal women fared worse than women who haven’t started the menopausal transition yet, but that those changes were limited to the time during the menopause transition; post-menopausal women demonstrated identical cognitive performance as pre-menopausal women.
In fact the memory declines and brain fog are temporary, with one study that followed 2,362 women for four years showing that memory and learning ability rebounded following the menopausal transition 
Have compassion for yourself – recognize that this is not under your control and that it is temporary. Support yourself with meditation, journaling, taking a green bath (e.g. walking in the woods!), napping if and when you can, or engaging your creative side through art and music. Consider letting some of the less-important things go, and don’t beat yourself up for forgetting details once in awhile. It will come back.
Have a conversation with family and friends about what you are experiencing, and ask for support and compassion. You may also want to seek professional help, individual therapy and/or counseling to learn tools for recognizing and working through these common but hidden symptoms of perimenopause.
Seek professional help, individual therapy and/or counseling to learn tools for recognizing and working through these common but hidden symptoms of perimenopause.
As much as you are able, emphasize a healthy lifestyle with enough quality sleep, good nutrition and physical movement – at least 30 minutes for five days per week. Visit the movement therapy, and nutritional therapy pages for more information on how to make positive changes in these areas. Cut down on alcohol, recreational drugs, and late nights.
Low levels of some nutrients may play a role in brain fog, although these nutritional inadequacies are not the only cause.  Research supports supplementing the following nutritional deficiencies to help improve symptoms of brain fog:
Vitamin D has been shown to impact mental health and depressive symptoms including brain fog. Vitamin D supplements may improve memory and concentration both of which are associated with brain fog. One randomized controlled trial (RCT) looked at vitamin D supplementation and cognitive performance in post-menopausal women and found that participants taking 2,000 IU/d vitamin D performed better in learning and memory tests compared to women taking 600 IU/d or 4,000 IU/d. 
Omega-3 fatty acids are known for their overall health benefits. Taking Omega-3 fatty acid supplements (specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)) can help improve memory, attention, and mood including depression and anxiety symptoms. 
Magnesium is an essential mineral, and low levels are associated with concentration difficulties among other brain fog symptoms. Magnesium with calcium is also helpful in reducing restless leg syndrome which strikes so many women in mid-life.
Vitamin C is known to support brain health. One recent study found that there is a significant association between vitamin-C concentrations in the blood and performance on tasks involving attention, focus, working memory, decision speed, delayed and total recall, and recognition. There was no difference based on the source of the vitamin C, so supplements were as effect as vitamin C obtained through normal food intake.
B complex vitamins are important for good brain function. One study looking at the impact of supplementing B12 vitamins in patients with cognitive deficits showed that of 202 study participants, 84% showed improvements in cognitive skills and 78% showed improved scores on memory and attention scores.  Other B vitamins including folate and vitamin B6 are also associated with brain fog, where low or deficient levels can make brain fog symptoms worse. Using a B complex supplement is a good approach to increase levels of all B complex vitamins.
L-theanine is a compound found in green tea. Not only has it been found to directly improve mental alertness and memory tasks, but it has also been shown to reduce tension and help increase calm and relaxation. Stress typically makes brain fog worse, so L-theanine works both directly and indirectly to support cognitive function. 
It can be very difficult to gain validation for menopausal transitional changes related to cognition so it is important to have a trusted health care provider. If you do not already have an educated primary care provider familiar with recognizing and treating perimenopause and menopause, the North American Menopause Society provides a list of menopause practitioners here.
Brain fog symptoms can be caused by multiple different conditions and factors, so it is very important to talk to your healthcare provider about what you are experiencing. Track these symptoms over time so that you have good data to share with your healthcare provider.
At this time, there aren’t any therapeutic drugs that treat brain fog directly.  There have been observational studies showing brain fog improvements after Hormone Therapy (HT) treatment, however, a recent study out of Stanford University concluded that there was no change in cognitive abilities associated with estrogen-only therapy for post-menopausal women, regardless of their age.  Note however, that this study was focused only on post-menopausal women – typically brain fog associated with the menopausal transition resolves itself once a woman reaches menopause.
Use of nutraceutical therapies (therapies that use food to provide medical or health benefits), may offer relief to some women, although currently there are no FDA-approved (i.e. clinically proven safe and effective) nutraceutical therapies.
The causes of cognitive impacts during the perimenopausal transition are an active area of research. One study looked into the neurological impacts of perimenopause rather than just focusing on changes in the reproductive system. Given that estrogen serves as a ‘master regulator’ in the brain, making sure that the brain responds correctly during energy metabolism, it isn’t surprising that when estrogen levels decline during the menopausal transition, there are impacts on the brain. It appears that the estrogen receptor network throughout the body becomes ‘uncoupled’ from the bioenergetic system (the metabolic system), changing the normal metabolic rate in a way that is associated with neurologic dysfunction.  This study also indicated that brain fog may result from swings in available glucose to the brain as shown in the graph. 
Brinton et al 2015
Different research showed that not only are there neurological symptoms during the menopausal transition, but brain structure is also affected. The study used brain imaging to scan the brain structure and found substantial differences in brain structure, brain connectivity, and energy metabolism across the different reproductive stages of premenopause, perimenopause and postmenopause. The regions of the brain showing changes are involved in cognitive processes. 
Systemic inflammation is correlated positively with emotional difficulties and “brain fog” or difficulties finding words and thoughts, during menopausal transition. One recent study showed that inflammation affected brain activity related to staying alert while other brain activity including selecting and prioritizing sensory information was unaffected. 
Brain fog is a normal and common symptom of the menopausal transition, but it is also a symptom of other, sometimes very serious, health conditions. Dementia is the common term describing loss of memory, language, problem-solving and other thinking skills that are severe enough to interfere with daily life. Alzheimer’s disease is the most common cause of dementia, and two out of three Alzheimer’s patients are women. It typically starts with memory lapses and then progresses, getting worse over time. Other symptoms of Alzheimer’s include:
If you have trouble with your memory, or other cognitive skills, that are impacting you on a daily basis, you should immediately see your healthcare provider.
There has been concern about the use of Hormone Therapy and its potential correlation with dementia. A 2005 study did find an increased risk of developing dementia among users of estrogen-progestogen therapy, but it is important to note that the participants in this study were all postmenopausal and still taking HT after age 65. 
A more recent review study assessed 118,501 women with a primary diagnosis of dementia to estimate the risk for developing dementia and Alzheimer’s disease. The study concluded that there are no increased risks of developing dementia overall in women using different types of HT for different durations. However, the study did find a slightly increased risk of developing Alzheimer’s disease specifically, for women who were long-term users of estrogen-progestogen therapies. This risk grew gradually over each year of exposure, reaching an average 11% increased risk for women with HT use of between 5 and 9 years and an average 19% for use of 10 years or more. 
While the obvious answer is found in gender, age and racial inequity, the study of mid-life women’s sexual and reproductive health has historically been less profitable than studying fertility. Thankfully the “menopause market” is on the rise, which will hopefully drive more dollars into the evidence-based scientific research that is so badly needed to develop more safe, effective and personalized treatments for menopausal women.
Unfortunately, women experiencing the menopausal transition continue to be excluded from the workforce where they feel embarrassed and isolated by their untreated symptoms. Slowly this is changing as employers and insurance companies start to realize that leaving the health concerns of this enormous group of workers unaddressed is costly.