Night shift work causes body 'chaos', scientists warn
21 January 2014 Last updated at 11:42 GMT
Night shift work causes "chaos" to the body and can cause long-term damage to health, researchers have warned.
Scientists at the Sleep Research Centre in Surrey found that sleeping at unnatural hours risked disrupting genes which control the body's daily functions.
Changes to the body clock could eventually cause damage to the immune system, depression, obesity and heart disease.
Professor Derk Jan-Dijk, who led the study, told BBC Radio 5 live's Breakfast: "This disruption causes... chaos in the carefully orchestrated separation of functions."