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Hello and welcome to more or less on the BBC World Service.

I'm Ruth Alexander.

This week, could having long lie-ins kill you? I try, although often fail to get

eight-hour sleep, which I always thought was the ideal. That is not true.

Until I heard from Dr. Greg Jacobs, a specialist at the Sleep Disorder Center at the University

of Massachusetts Medical School in the US.

We were given that recommendation for many years and now the research over the past 10 years

suggests that sleeping eight hours a night may be a health risk.

So Greg believes that getting 8 hours sleep a night might actually be bad for you.

There have been about 34 studies. These are epidemiologic studies that follow people over time involving over 2 million people that consistently show that there's a U-shaped relationship between sleep duration and mortality.

The lowest mortality is at the bottom of the U and that's seven hours and

...