Why are conditions such as chronic stress, depression, cardiovascular disease, fragmented sleep, and aging all associated with a higher risk of dementia? In a new review piece published in Science, University of Rochester Medicine neuroscientist Maiken Nedergaard, MD, DMSc, proposes that many of these seemingly different conditions may converge on the same biological problem: disruption of a sleep-dependent brain rhythm that helps clear waste from the brain. This process, known as glymphatic clearance, is particularly active during deep sleep and appears to be crucial for maintaining brain health. Nedergaard's research team has been studying this phenomenon for years, finding that the brain's tissue expands by 60% when we are asleep, allowing cerebrospinal fluid (CSF) to flush out waste products.
This process is thought to play a key role in removing toxic proteins and other debris from the brain that can contribute to conditions like Alzheimer’s disease. According to Nedergaard, fragmented sleep or chronic stress may interfere with this natural cleaning mechanism, leading to an accumulation of harmful substances in the brain. She notes that as we age, this process becomes less efficient, further increasing the risk of cognitive decline and dementia. The findings suggest a potential new avenue for treating neurodegenerative diseases.
By developing therapies that enhance glymphatic clearance or improve sleep quality, researchers may be able to mitigate some of the negative effects associated with these conditions. However, more research is needed to fully understand how disruptions in this brain rhythm contribute to cognitive decline and dementia. Understanding the link between sleep, waste clearance, and neurodegenerative diseases could pave the way for new treatments that target this overlooked aspect of brain health. As Nedergaard emphasizes, "If we can find ways to improve glymphatic clearance or enhance our sleep quality, it may be possible to reduce the risk of dementia in older adults."
