Lack of sleep affects the body and health: it can affect memory, lethargy, lack of concentration... A day lasts 24 hours: 8 hours to work, 8 hours to sleep, 8 hours to do something else. A healthy amount of sleep for adults is 7 to 8 hours. There are several sleep cycles: half-asleep, deep sleep and full sleep, which can include dreams that you remember when you wake up. Hygiene and health’ programme with Radio Don Bosco.