A week without getting seven to eight hours’ sleep a night

We all know that even a single night of disrupted sleep can affect mood and alertness. “Try not to catch up on sleep by having a lie-in or napping in the day, as that disturbs your body clock,” she says. “We can realistically achieve a 15-minute change in our body clock schedules each day, so don’t aim for massive adjustments in bedtime; maybe just aim to go to bed 15 minutes or so earlier to get back into a better routine.” Keep your bedroom cool and dark and avoid working there if you can.

Slower Reaction: “Just 18 hours without sleep is comparable to having blood alcohol levels of 0.1 per cent,” says David Ray, a professor of endocrinology at the University of Oxford. “Since a blood alcohol content of 0.08 per cent counts as legally intoxicated in the US, it gives an indication of how much slower your reaction times and potential for making mistakes will be.”

Health impact: Sleep scientists at the University of Surrey found volunteers subjected to a week of no more than six hours’ sleep a night experienced disruption to hundreds of the body’s genes, including those associated with metabolism, immunity and the body’s circadian rhythm.

Lowers Muscle Mass: Sleep disruption leads to raised levels of cortisol, the stress hormone, which affects the body’s ability to build and repair muscle according to Richard Kirwan, a researcher in the school of biological and environmental sciences at Liverpool John Moores University. He says that “this could have a significant effect on muscle mass and strength over time”.

Increased consumption of higher calorie & lower nutritionally dense foods: We eat more (and of the wrong foods) when we are tired, according to Dr Nicola Barclay, a lecturer in sleep medicine at the University of Oxford’s Sleep and Circadian Neuroscience Institute.

Overall: In the long-term, sleep loss is associated with a raised risk of obesity as well as raised blood pressure and cardiovascular disease, so it’s important to re-establish a healthy sleep routine as quickly as you can.

How to reset your sleep cycle: Barclay says. “Try not to catch up on sleep by having a lie-in or napping in the day, as that disturbs your body clock,” she says. “We can realistically achieve a 15-minute change in our body clock schedules each day, so don’t aim for massive adjustments in bedtime; maybe just aim to go to bed 15 minutes or so earlier to get back into a better routine.” Keep your bedroom cool and dark and avoid working there if you can.