A lack of sleep among the U.S. workforce is costing approximately $411 billion and losing 1.2 million working days per year, a new study has found.

The study, titled ‘Why sleep matters – the economic costs of insufficient sleep’, was conducted by researchers at non-profit organisation RAND Europe and is the first of its kind to quantify the economic impact of sleep deprivation. Researchers found that a person who sleeps on average less than six hours a night has a 13 percent higher mortality risk than someone sleeping between seven and nine hours.

Marco Hafner, a research leader at RAND Europe and the report’s main author, said “Our study shows that the effects from a lack of sleep are massive. Sleep deprivation not only influences an individual’s health and wellbeing but has a significant impact on a nation’s economy, with lower productivity levels and a higher mortality risk among workers.”

The U.S., UK, Canada, Germany, and Japan were investigated as case study economies, with the U.S. sustaining by far the highest economic losses. In relative terms however, Japan suffers the largest economic loss, losing 2.92 percent of GDP due to sleep deprivation among its workforce, compared to the U.S. with 2.28 percent.

RAND Europe’s research was released on Tuesday, a day before Arianna Huffington launched her new company Thrive Global, which advocates the importance of better sleep for increased productivity.