According to researchers, everyone on the planet should be logging at least seven hours of sleep a night. Fewer than that has been linked with health problems including cardiovascular disease, obesity, depression and injuries. Yet a lack of sleep affects about 40 percent of the population, with roughly 20 percent of people suffering from insomnia. It's a problem that results in 1.2 million lost work days a year at about a $411 billion cost to the economy.

If better, more restful sleep is something you'd like to benefit from, take some tips from University of Oxford sleep expert, Professor Colin Espie. As cofounder of Big Health, creators of Sleepio, a digital sleep-improvement program featuring cognitive behavioral therapy, here's his advice about what you can be doing to get better quality sleep, and more of it.

1. Use afternoon naps sparingly.

They may disrupt your ability to fall asleep at night. However, if you are behind on your sleep you'll be carrying around a sleep debt which will make you feel fatigued. A nap of 10 to 15 minutes can help and shouldn't overly affect your sleep pattern. Just don't overuse this.

2. Behave as if you're on a holiday.

Are you someone who sleeps better while on vacation? If so, it may be that on holiday you use your smartphone less and sleep in room devoid of stress. This is a literal and mental escape which you can recreate at home. To do it, avoid gadgets before bed, and keep the lights down. Electronics and artificial lights emit blue light which suppresses a person's circadian rhythm and the secretion of the sleep hormone melatonin.

3. Practice progressive relaxation.

It's a proven method for getting to sleep easier and involves lying in bed, slowly tensing and then relaxing each of your muscle groups, one at a time. Do this while breathing slowly and deeply and thinking the word "relax" with every exhalation.

4. Put the brakes on a racing mind.

To counteract insomnia caused by over-thinking, remove the emotional context related to problems. In other words, try to look at the situation bothering you as an outsider, or using a longer-term perspective. Will the issue matter in a year? In five years? Chances are, it does not require your mental energy in the middle of the night.

5. Track your sleep.

Gadgets which can do so are widely available and can help you identify the kinds of things which may be triggering wakefulness. From there, more high quality sleep can be achieved by changing unhelpful thinking habits through cognitive behavioral therapy. "Sleepio provides an entire clinically-proven course based on [it], which is personalized to individuals using tracked sleep data."