The new science of sleep

What we don’t know about sleep could fill a library. But recent research reveals just how fundamental quality rest is for longevity

In a 2019 study, researchers showed that during deep sleep, gaps between your brain cells open up, allowing cerebrospinal fluid – a clear liquid that surrounds your brain and spinal cord – to wash in and out of your brain, like a wave. It’s thought that this fluid flushes out sticky build-ups of toxic proteins that are thought to be involved in the development of Alzheimer’s and other neurodegenerative diseases. A working theory is that deep sleep is necessary for this activity to take place.

Sleep physiologist Guy Meadows points to a 2021 study published in the European Heart Journal, which showed that women who experienced unconscious wakefulness (when your body wakes up to respond to a potential danger, such as your breathing being obstructed, but which you don’t remember in the morning) most often and for longer periods of time had nearly double the risk of dying from cardiovascular disease during an average of between six and 11 years’ follow-up, when compared with the risk in the general female population. Further research is needed, but the thinking is that sleep affects processes such as blood pressure and inflammation, which are associated with cardiovascular disease.