“O bed! O bed! delicious bed!
That heaven upon earth to the weary head.”
To Sleep, Perchance to Dream
We spend 1/3 of our lives sleeping (and the other 2/3 probably binge-watching Netflix). Even if you’re a “short sleeper,” a large part of the day is taken up by a phenomenon that we still know so little about (why we even need it in the first place is still debated).
Nevertheless, sleep is an infinitely important biological phenomenon, during which our bodies undergo many restorative processes; memory consolidation, mood regulation, clearance of brain metabolites, appetite regulation, immune/hormonal function, and tissue regeneration, among others.
While the cognitive and physical (performance) benefits of sleep have been well documented (as have the adverse effects of not getting enough), the profound consequences that sleep has on regulating, restoring, and maintaining the optimum functionality of the cardiovascular system have recently been getting more attention. Sleep, we now know, is a time during which profound modification of the cardiovascular system occurs. This modification serves a purpose — we don’t just “turn off” or “slow down” during sleep. In fact, during some aspects of sleep (such as REM), some common physiological processes are actually enhanced (for example, your blood pressure and heart rate increase).
As such, the processes that occur during sleep to maintain systemic CV health, including a lowering of heart rate and arterial blood pressure (during non-REM sleep) serve to give our bodies a “break” from the high cardiac output, stress on the heart, and pressure demands on our blood vessels and organs that we encounter during the day. A withdraw in sympathetic nervous system activity(the system that regulates the “fight or flight” response) and an increase in parasympathetic activity (sometimes called the system for “rest and digest”) accounts for these nocturnal happenings.
What happens when these systems go awry — when we either forgo sleep (voluntarily or involuntarily) for a certain period of time (say, 24 hours) or undergo a more chronic form of sleep deprivation/restriction, such as is seen in modern day society (we sleep profoundly less than we used to — with an almost doubling in the number of adults sleeping <6 hours in 2012 compared to 1985)?