For staff at insurance group Aetna, it pays to get a good night's sleep. Specifically $300 (£225) a year. Such is the US firm's concern about the impact of sleep deprivation on employee performance, that it encourages its workers to sign up to a scheme that rewards them for getting at least seven hours of shut-eye per night. Aetna staff that participate can earn $25 for every 20 nights in which they sleep seven hours or more, up to a limit of $300 every 12 months. Introduced in 2009, about 12,000 of the firm's 25,000 employees participated last year, an increase from 10,000 in 2014. Staff are trusted to manually record how long they have slept every night. Kay Mooney, Aetna's vice-president of employee benefits, says that the sleep scheme is "one of many different healthy behaviours we wanted staff to track". The firm's staff also receive extra funds if they do exercise. Aetna's commitment to ensuring that its workers get enough sleep comes as a number of studies warn that not sleeping long enough can significantly affect our ability to do our job.