But the average night's sleep in the UK now averages about 90 minutes less than it did in the 1920s, when it was 9 hours per night. Physical frailness, as well as mental and physical exhaustion. Sleep is made up of different stages. Stage 2 is deeper and lasts about 20 minutes. Stages 3 and 4 come after this, and are types of deep sleep.
Deep sleep is the part of sleep that our body and brain needs to recover from the day.
It sometimes called delta sleep, after the delta waves the brain generates. We don't dream during this time. During a normal night, people usually cycle through the various stages several times. Problems arise when the pattern of cycles is broken. Researchers at Loughborough University's Sleep Research Laboratory have found that people are designed for 2 sleeps a day - the main one at night, and a nap in the afternoon.