I barely thought about sleep in my 20s; whether I got four or eight hours didn’t seem to make much difference to how I felt the next day. A couple of decades later and it’s a different story: a night spent tossing and turning leaves me headachey and prone to travel sickness and brain fog.
These hangover-style symptoms that worsen with age are our body’s way of telling us we’re missing out on something important. Research shows that sleep is no less fundamental to physical and mental wellbeing than diet and exercise. It is driven by two biological rhythms: sleep/wake homeostasis, which is determined by when we last slept, and circadian rhythm, the body’s internal 24-hour clock which is triggered by light and dark, and controlled by the part of our brain that regulates hormone levels that affect body temperature, appetite and sleepiness.
