A lack of sleep can cause mental health problems including anxiety and depression, but it also impacts on productivity and concentration at work.

A survey by Big Health, published to coincide with World Sleep Day on Friday, shows the average employee loses 8.5 days work a year because they can’t drop off at night.

Big Health, creators of the sleep improvement app Sleepio, said sleeping pill prescriptions cost the NHS £50 million every year.

People classifying themselves as poor sleepers admitted to missing nearly 15 days a year in lost productivity, yet 60% said they hadn’t sought a solution to the problem from a doctor.

Of the 2,500 respondents to the World Sleep Survey, most said poor sleep impacted energy levels, while others said it affected their mood and relationships with others.

“World Sleep Day is the perfect time to acknowledge the widespread effect poor sleep has on our lives,” said Colin Espie, co-founder of Big Health and professor of sleep medicine at the University of Oxford.

“Sleep is not an optional extra in life; it is a fundamental requirement. The consequences of a bad night’s rest affect us not only physically but also mentally and emotionally, seriously impacting our performance at work.

“Physically we will feel lethargic, mentally we become slowed down with poorer concentration and memory, and emotionally we may become irritable and rather down, with bursts of hyperactivity. In terms of daily life, no aspect of daily functioning is unaffected by sleep - least of all our jobs.”

World Sleep Day is an annual event taking place on the Friday of the second full week in March. It has been organised by the World Association of Sleep Medicine since 2008.