Menopause, Brain Fog, and Neurometabolism: What the Research Is Showing

Many women in their 40s and 50s describe a similar experience: they notice that their thinking has changed. Words do not come as quickly. They walk into a room and forget why. They feel less confident in their cognitive abilities than they used to. They may be sleeping poorly, feeling more anxious, or experiencing a kind of mental fatigue that is different from anything they have felt before.

These experiences are often attributed to stress, ageing, or the general demands of midlife. But there is a growing body of research suggesting that hormonal change during perimenopause and menopause has specific, measurable effects on brain function — and that these effects deserve to be taken seriously, not dismissed.

Oestrogen and the Brain

Oestrogen is not just a reproductive hormone. It plays a significant role in neurological function — influencing neurotransmitter systems, cerebral blood flow, glucose metabolism, synaptic plasticity, and neuroprotection. Oestrogen receptors are found throughout the brain, including in regions critical for memory and executive function such as the hippocampus and prefrontal cortex.

During perimenopause, oestrogen levels fluctuate significantly before declining. This fluctuation — rather than simply the eventual low oestrogen state of postmenopause — is associated with many of the cognitive and mood symptoms that women report during this transition. The brain is adapting to a changing hormonal environment, and that adaptation is not always smooth.

The Neurometabolic Connection

One of the most significant areas of emerging research concerns the relationship between oestrogen and brain energy metabolism. Oestrogen appears to support the brain's ability to use glucose efficiently. As oestrogen declines, some research suggests that the brain may shift towards less efficient energy substrates — a change that could contribute to cognitive symptoms, fatigue, and mood disturbance.

This neurometabolic perspective helps explain why cognitive symptoms during menopause often co-occur with metabolic changes — including changes in body composition, insulin sensitivity, and energy regulation. Addressing metabolic health during this transition is not just about weight or cardiovascular risk — it may have direct implications for brain function.

Sleep disruption and its downstream effects

Vasomotor symptoms — hot flushes and night sweats — are among the most common features of perimenopause and menopause, and they frequently disrupt sleep. As discussed in the article on sleep and the glymphatic system, poor sleep quality has significant downstream effects on cognitive function, mood, and brain-health risk. Addressing sleep disruption during this transition is one of the most important interventions available.

HPA axis and stress physiology

The hormonal changes of perimenopause also affect the HPA axis — the stress-response system. Many women notice that they feel more reactive to stress during this transition, that their nervous system feels less resilient, and that anxiety emerges or worsens. This is not simply psychological — it reflects real changes in the neuroendocrine system that influence mood, cognition, and stress tolerance.

Thyroid function

Thyroid dysfunction — including subclinical hypothyroidism and Hashimoto's thyroiditis — is more common in women and tends to emerge or worsen during the perimenopause transition. Thyroid symptoms overlap significantly with menopause symptoms: fatigue, brain fog, mood changes, weight changes, and sleep disruption. A comprehensive thyroid assessment is often warranted when cognitive symptoms emerge during this period.

"The cognitive symptoms of perimenopause are not imagined, not inevitable, and not simply a matter of waiting for the transition to be over. They are worth investigating."

What an Assessment-Led Approach Looks Like

Jo Grabyn's approach to cognitive symptoms during perimenopause and menopause begins with a comprehensive assessment of the full picture — not just hormones, but sleep, metabolic health, thyroid function, nutrient status, stress physiology, and lifestyle patterns. The goal is to understand which contributors are most relevant for the individual and to build a practical, prioritised plan.

This work sits alongside — not instead of — appropriate medical care. If hormone therapy is relevant and appropriate, that conversation belongs with a GP or specialist. Jo's role is to address the broader functional picture and support the brain-health foundations that are within the scope of nutritional and lifestyle medicine.