Sleeping in over the weekend is one of life’s great pleasures. Yet some of us are much better at it than others. A teenager is much more likely to emerge from their bed at midday than their middle-aged parents – but even within age groups, individual differences exist.
Why is this? It’s well-known that teenagers tend to sleep later than mature adults, and we all have our natural rhythms. But we’re not actually the slaves to our body clocks you might think. If you find getting out of bed on a Sunday hard even after a long night’s sleep, there may be something you can do about it.
The body clock generates rhythms so that we are alert during the day while body temperature is high and sleep at night while body temperature is low. This clock has evolved to match the cycle of light and dark, and associated cycles of temperature, for example, created by the Earth’s rotation. But what happens now that artificial light means that we are in control of this cycle?