Getting a consistent seven- to nine-hours of sleep each night is the single most effective thing each of us can do for our health and wellbeing.
Matthew Walker, writing for The Guardian:
Related is the association between plentiful slumber and athletic performance. Sleep is perhaps the greatest legal performance-enhancing “drug” that few people are taking advantage of. Obtain less than eight hours of sleep a night, and especially less than six hours a night, and the following happens: time to physical exhaustion drops by 10 to 30%, as does aerobic output; limb extension force and vertical jump height are reduced; peak and sustained muscle strength decrease. Add to this the cardiac, metabolic and respiratory effects: higher rates of lactic acid buildup and reductions in blood oxygen saturation with converse increases in carbon dioxide, due in part to a reduction in the amount of air that the lungs can expire in a sleep-deficient state. And then there is injury risk. Relative to sleeping nine hours a night, sleeping five to six hours a night will increase your chances of injury across a season by more than 200%.
Routinely sleeping less than six hours a night also compromises your immune system, significantly increasing your risk of cancer. So much so, that recently the World Health Organization classified any form of night-time shiftwork as a probable carcinogen.
Inadequate sleep – even moderate reductions of two to three hours for just one week – disrupts blood sugar levels so profoundly that you would be classified as pre-diabetic. Short sleeping increases the likelihood of your coronary arteries becoming blocked and brittle, setting you on a path towards cardiovascular disease, stroke and congestive heart failure.
All it takes is one hour of lost sleep, as demonstrated by a global experiment performed on 1.6 billion people across more than 60 countries twice a year, otherwise known as daylight saving times. In the spring, when we lose one hour of sleep, there is a 24% increase in heart attacks the following day. In the autumn, we gain an hour of sleep opportunity, and there is a 21% reduction in heart attacks.
It’s been repeatedly shown that sleep is essential to how we form memories.
The human brain requires we sleep roughly one third of every day to properly process and store thoughts so they can be remembered at a later time. Depriving ourselves of sleep, especially over the long term, can disrupt this process. And it can make learning more difficult.
Researchers at the Sleep Research Laboratory at the University of Ottawa have found that once you drift off, your brain shifts information from the hippocampus, which is only used to store recent memories, to the prefrontal cortex. It’s how we learn new things, and remember them for the future.
A short night of sleep may translate into learning less. Our brain requires suffecient time to store everything it took in during the day. Researchers say it’s clear that if you want to be smarter, you may need to sleep more.
The waking brain is optimized for collecting external stimuli, the sleeping brain for consolidating the information that’s been collected. At night, that is, we switch from recording to editing, a change that can be measured on the molecular scale. We’re not just rotely filing our thoughts—the sleeping brain actively curates which memories to keep and which to toss.
It doesn’t necessarily choose wisely. Sleep reinforces our memory so powerfully—not just in stage 2, where we spend about half our sleeping time, but throughout the looping voyage of the night—that it might be best, for example, if exhausted soldiers returning from harrowing missions did not go directly to bed. To forestall post-traumatic stress disorder, the soldiers should remain awake for six to eight hours, according to neuroscientist Gina Poe at the University of California, Los Angeles. Research by her and others suggests that sleeping soon after a major event, before some of the ordeal is mentally resolved, is more likely to turn the experience into long-term memories.