Computers, tablets and smartphones are contributing to an epidemic of sleep deprivation, new research has suggested.
A survey indicates that more than 28 million people in the UK - almost six in 10 of the population - are regularly getting no more than seven hours sleep a night.
It also shows that 78% of Britons are exposed to sleep-disruptive blue light from computer devices before going to bed.
Among 18 to 24-year-olds included in the 2,149 adults questioned, this figure rose to an astonishing 91%.
"The blue light from these devices suppresses the production of the sleep-inducing hormone melatonin, so it's important to avoid them before bed time," said psychologist Professor Richard Wiseman, who commissioned the YouGov poll.
The amount of sleep we need varies between individuals but adults generally require a minimum of seven to eight hours a night.
Teenagers need more, around nine hours, but often do not get enough.
The proportion of people thought to be getting too little sleep had risen by a fifth since a "bedroom poll" conducted last year by the National Sleep Foundation.
"This is a huge rise, and the results are extremely worrying because getting less than seven hours sleep a night is below the recommended guidelines, and is associated with a range of problems, including an increased risk of weight gain, heart attacks, diabetes and cancer," Prof Wiseman, from the University of Hertfordshire, said.
Participants in the new study were asked if they used a computer, tablet or smart phone in the two hours before going to bed.
The results were timed to coincide with publication of Prof Wiseman's book Night School, which looks at the science of sleep and dreaming.
The survey also investigated dreams and found that for many participants they were far from sweet.
Just 10% of respondents agreed with the statement: "I would describe my dreams as pleasant".
Prof Wiseman has compiled 10 science-based tips to help people get a better night's sleep.
:: Banish the blues: Avoid using computers, smartphones or tablets in the two hours before going to bed. The blue light stimulates the brain and keeps you awake.
:: The list: Make a list of all of the things you have to do the next day or that are playing on your mind. This helps prevent you poring over these issues in bed.
:: Tire your brain: If you are struggling to sleep, make your brain tired by thinking of an animal for each letter of the alphabet (A is for Ant, B is for Bear, etc).
:: Move your bed: You have evolved to feel safe when you can spot danger early and have time to run away. This means you will feel most relaxed when your bed faces the door and is far away from it.
:: Reach for a banana: Eat a banana before you head to bed. They are rich in carbohydrates, which help relax your body and brain.
:: Employ reverse psychology: Actively trying to stay awake actually makes you feel tired, so try keeping your eyes open and focus on not falling asleep.
:: Wear socks: If you have bad circulation, your feet will get cold and cause sleeplessness. To avoid the problem, wear a pair of warm socks in bed.
:: Avoid nightcaps: Although a small amount of alcohol puts you to sleep quicker, it also causes a more disturbed night and disrupts dreaming.
:: Engage the power of association: Ensure the same piece of soporific music is quietly playing each time you fall asleep. Over time, you will associate the music with sleep, and listening to it will help you to nod off.
:: Do a jigsaw: If you lie awake for more than 20 minutes, get up and do something non-stimulating for a few minutes, such as working on a jigsaw.