Matthew Walker, author of Why We Sleep: The New Science of Sleep and Dreams:

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.

Strikingly, all it takes is one hour of lost sleep, as demonstrated by a global experiment 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. Most of us think little of losing an hour of sleep, yet it is anything but trivial.

Sleep disruption has further been associated with all major psychiatric conditions, including depression, anxiety and suicidality. Indeed, in my research over the past 20 years, we have not been able to find a single major psychiatric condition in which sleep is normal.

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Put simply: sleep – a consistent seven- to nine-hour opportunity each night – is the single most effective thing we can do to reset our brain and body health each day.