NHS Choices suggests a 'normal' amount of sleep for an adult is around seven to nine hours a night, more for children, and possibly less for older adults. However, it says that what is important is whether the person feels like they are getting enough sleep, and whether it is of good quality.

It provides some guidance around sleep requirements for infants and children, based on work undertaken by Millpond Children's Sleep Clinic. This gives approximate hours of daytime and night time requirements up to the age of three years. For the first three months this amounts to around 16 hours a day (evenly split between day and night at birth), with the ratio changing by 12 months old to 2-3 hours of daytime sleeping and 11 hours at night.7

For toddlers, the suggested amount of required daytime sleep continues to fall, with night-time sleep being up to 12 hours. By four years onwards sleep requirements are just for night time: 11 hours for five-year olds; 10 hours for nine-year olds; and nine hours for 14-16-year olds.