An accountant I know who deals with balance sheets all day suddenly couldn't remember the word revenue. A detail-oriented marketing executive has to read every memo three times instead of once.

Another friend forgets the storyline of television shows within a day. None of these women are losing their minds, even though it can feel that way. What they are losing is estrogen, which affects the brain wiring responsible for memory and how fast you process information. Combine that with a lack of sleep common in menopause and you have a perfect recipe for brain fog.

“Estrogen is to the brain what fuel is to an engine,” says Lisa Mosconi, PhD, associate professor of neuroscience in neurology and radiology at Weill Cornell Medicine. “Estrogen, particularly estradiol, the strongest form, plays a critical role in the brain’s health and functionality, earning it the title of the ‘master regulator’ of women’s brain health. When estrogen is in the house, everything works well.” She explains the four key roles estrogen plays. It helps protect neural structures and cells from damage and promotes the survival of neurons. It is involved in cognitive processes such as memory, learning, and executive functions. It influences mood and emotional well-being, acting on serotonin and other neurotransmitter systems. And finally, estradiol promotes the growth of new neurons and supports neuroplasticity, including the brain’s ability to change and adapt.

“After menopause, the decline of estrogen impacts all of these brain functionalities. It’s akin to an orchestra that continues to play but to a markedly different tune,” Mosconi says. “Without the guiding influence of estrogen, the brain’s regulatory mechanisms, protective functions, and cognitive processes may be altered, potentially leading to changes in memory, mood, and overall brain health.”