How much sleep do you need and is more than eight hours really that dangerous?

New research has suggested that people who sleep for more than eight hours a day are more likely to have a stroke, adding to a wealth of advice and information about the optimal time to spend in bed.

The new warning may seem farfetched, but it comes from a comprehensive study carried out at Cambridge University on the sleep patterns of more than 10,000 people. Those who got eight hours had a 46 per cent greater than average stroke risk.

Oversleeping (usually defined as more than nine hours a night) has previously been linked with health problems like diabetes and obesity – yet few consider eight hours to fall into that bracket.

Sure enough, the National Sleep Foundation (UK) recently published new guidelines, produced with a team of medical scientists, to try and pin down exactly how much sleep we need.

They defined the ideals, by age group, as follows:

Newborns (0 – 3 months): 14-17 hours per day

Infants (4 – 11 months): 12-15 hours per day

Toddlers (1 – 2 years): 11-14 hours per day

Pre-school children (3 – 5 years) 10-13 hours per day

School age children (6 -13 years) 9-11 hours per day

Teenagers (14 – 17 years) 8-10 hours per day

Younger adults (18 – 25 years) 7-9 hours per day

Adults (26 – 64): 7 – 9 hours per day

Older adults (65 years+) 7-8 hours per day

Despite first appearances, the foundation probably not recommending an amount of sleep likely to make people have strokes.

The latest study does not make clear whether extra sleep is causing health issues or simply an indicator or symptom of underlying conditions.

Professor Kay-Tee Khaw, of the Cambridge Institute of Public Health and the study’s senior author, said “further research” was needed to establish what was “happening in the body to cause this link”.

And Dr Madina Kara, research manager at the Stroke Association, said the study did not amount to evidence that too much sleep led to stroke, and urged anyone with concerns about their health to speak to their GP.