Work time is the single most important lifestyle factor that impacts on sleep - the more hours you work the less sleep you get - research suggests. Those who got less than four-and-a-half hours sleep a night worked an average of 93 minutes longer on weekdays and 118 minutes more on the weekend. Commute time ranked second, above socialising and leisure time, for eating into sleep time.

The study in the journal Sleep included nearly 50,000 US participants They were surveyed on three different occasions - in 2003, 2004 and 2005 - and asked how they spent their time between 4am the previous day and 4am that day. Time spent working had the biggest impact on sleep time.

Those who slept 11-and-a-half hours or more worked an average of 143 minutes less on weekdays and 71 minutes less on weekends than the average sleeper.

Short sleepers also spent more time socialising, studying and doing housework.

In comparison, time spent watching TV increased with longer sleep times.

The age group that slept the least and worked the most was 45- to 54-year-olds, Dr Mathias Basner, of the University of Pennsylvania, and his colleagues found.

Dr Basner said more work was now needed to measure what impact long working hours encroaching on sleep might be having on health.

Jessica Alexander from The Sleep Council said: "Survey after survey confirms that people are burning the candle at both ends more and more, with no let-up on increasingly global working environments that demand long working hours and 24/7 leisure opportunities.

"Modern technology has done nothing to free up our time and sleep length and quality is the victim.

"Eventually business, government and the medical profession will have to give sleep as much priority in their healthy living messages as diet and exercise - if not more.

"In the meantime, The Sleep Council will continue to spread the word and advise people how to improve their sleep quality, if not quantity, through simple lifestyle and environmental changes."

Experts generally agree that seven to nine hours of sleep a night is advisable for adults.

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