Sleep is essential for brain health. Professor at UC Irvine in the Department of Cognitive Science and WAM Grantee, Dr. Sara Mednick, shares all you need to know about how sleep affects the brain.

WAM: What is the connection between getting sleep and having a healthy brain? What’s happening inside the brain when you’re asleep that is important for brain health?

Mednick: Sleep is an essential need for all aspects of health as it provides for restorative processes for all our hard working systems, including the cardiovascular, metabolic, cognitive, emotional, physical, and other systems. When we are awake and actively going about our day, we are using up a lot of resources that get replenished each night and the junk that are by-products of living gets washed away only during sleep. For example, the brain and body have plumbing systems that are active only during sleep that wash away toxins, and when you don’t get enough, you have a build-up of these toxins that can lead to plaques in the brain that are associated with Alzheimer’s disease. Along with cleaning crews, the brain also engages in solidifying connections between recent experiences and our knowledge and memory networks, which helps file memories into long-term storage and integrate our experiences into an understandable framework.

WAM: Women have worse sleep. Why? And is this related to their increased risk for Alzheimers?

Mednick: Women do report worse sleep than men, less restorative sleep and more problems with fatigue during the day. There are many potential reasons for this sex difference and not all of them are biological. Women have more daytime responsibilities including working full time jobs and doing the majority of the work on the domestic front. The wage gap between women and men also means that they have more stress from financial difficulties and increased stress has been linked with poor sleep. Biologically speaking, women experience fluctuations in their sex hormones on a monthly basis during their reproductive years, and a steep drop in sex hormone during menopause. Though there is a protective value from female sex hormones across many domains of functioning, the fluctuations themselves can lead to poor sleep, and changes to mood and cognition. It is not known whether there is a direct connection between these hormone-related changes and the increased vulnerability to Alzheimer’s disease, but it’s likely that there is some connection. 

WAM: You are doing a study funded in part by WAM right now. What are you trying to discover? What’s your hope?

Mednick: The study that WAM is funding in my lab will examine menopausal women to investigate whether brain functioning during sleep is related to long-term memory abilities and whether these effects are mediated by menstrual phase. Women who are experiencing menopause are brought into the lab during two phases of the menstrual cycle (high hormone phase and low hormone phase) in order to examine how sex hormones may affect their sleep and memory processing. Women take cognitive tasks in the evening and then go to sleep and in the morning we retest them on the same cognitive tasks to see how their cognitive performance changed across the night. We are using the cutting-edge technology of simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) to investigate the brain activity during cognitive testing and also during difference stages of sleep. We hope to discover differences in brain activity between the two menstrual phases that can account for differences in sleep-dependent cognitive changes.