No-one quite knows why a bit of shut-eye is good for us, but, says Renee Watson, it certainly is

The sun is shining, daffodils are brightening up every verge and the birds are out in force singing their merry tune.

It’s spring and I am here to tell you that no other time of year is more exhausting and infuriatingly perky.

Yes, I am a Spring Grinch.

It’s not that I don’t cherish the sight of new life and relish the long-awaited vitamin D boost, it is the havoc that is wreaked with my precious sleep.

I mean who needs an alarm when you have a nest of over-sharing blue tits just outside your window?

And aside from being hungry, nothing messes with my usual happy demeanour than a disrupted night’s sleep.

In evolutionary terms our need for daily sleep seems counter-intuitive.

We lay ourselves completely vulnerable to predators for long periods of time and we wouldn’t do that unless it was incredibly important. So why do we sleep and how much do we really need?

Surprisingly, the evidence for why we sleep is currently inconclusive, with a number of theories each offering interesting pieces of the puzzle.

The restorative theories suggest that we sleep because it gives our body a chance to recharge.

The energy conservation theories suggest that sleep is a way to be more efficient with the food we eat by savouring the energy we consume. Essentially like a mini-hibernation every night.

Research has shown a correlation between excessive sleep and obesity, which may support this theory.

The brain plasticity theory is the most recent addition to our understanding of sleep and suggests that it is essential for brain development.

Not only does sleep allow for the processing and storage of information learned during the day, it is also a time when the structure and organisation of our brain actually changes. These changes were particularly pronounced in children, supporting the view that substantial amounts of sleep (in the region of 12-13 hours per night) are important for brain development.

Controversy around sleep is not only in the “why” but also in the “how much”.

There are four stages in the sleep cycle and the key to a good sleep is to wake at the right point in the cycle as well as the number of cycles you complete.

The first two stages of the sleep cycle take between 10 to 30 minutes.

Stage one is the falling asleep stage, where, if you wake, you don’t feel like you have been asleep at all.

In stage two you are entering a deeper sleep where you brain starts switching off responses to the environment around you.

By stage three you are in a really deep sleep. Your muscles have been made to completely relax and many of your body processes are slowed right down. If you wake during this phase you feel rotten, while your body desperately tries to play catch-up, bringing all those hibernating processes back to life. This is called sleep inertia and it is likely to leave you with the feeling that you really needed more sleep.

The fourth sleep phase is Rapid Eye Movement or REM sleep. This is dream territory and the most difficult stage to wake from, with extensive muscle paralysis while the brain, conversely, is very active. The average adult reaches REM sleep every 90 minutes. It is thought that by school age most children are in a similar rhythm, whilst it takes only 50 minutes for a baby to complete its sleep cycle.

Taking all this information about how sleep works into consideration we can start working out that around eight hours of sleep per night is the magic number. Research shows that people who sleep around eight hours each night have the best reaction times.

People who sleep six hours per night for extended periods of time were found to have reaction times similar to those of someone who is legally drunk, and those with just four hours sleep were asleep in their cereal.

Naps have also been shown to be hugely beneficial, but only if the nap time is less than 30 minutes, preventing you from entering that deep sleep phase.

Likewise, hitting the snooze button on your alarm can be a big mistake. If it takes you into a deep sleep phase you will probably wake up feeling much worse than if you had have just got up in the first place.

The longest period of zero sleep anyone has recorded is 11 days... how many days until summer?!