In the first years of life most people fall asleep quickly and deeply. At the beginning of life, sleep is distributed throughout the day in several short cycles and the REM phase occupies the greater part of the night since it is essential for the growth and cognitive development of children.

Soon, wakefulness and sleep are differentiated into two clearly divided phases during each 24 hours, even though children need to sleep more hours at night and need at least one nap during the day in early childhood.

Throughout adult life the number of hours of sleep decreases and the REM phase is significantly reduced at the expense of an increase in slow waves or deep sleep. As we age, we have more difficulty sleeping and getting continuous, deep, restful sleep since nocturnal awakenings become more frequent and longer. During the day, daytime sleepiness increases, resulting in small involuntary naps in resting situations that contribute to the problem of nocturnal sleep. A commonly held belief is that the elderly need less sleep than adults and children, which is not quite true. What really happens is that age reduces our ability to stay asleep, as well as our ability to stay awake. In other words, the mechanisms that regulate wakefulness and sleep lose some of their effectiveness.

On the other hand, during the third age of life the opportunities to fall asleep during the day increase as a result of the decline in physical activity and the increase in sedentary activities, contributing to a greater alteration of sleep-wake patterns. Although the elderly spend the same amount of time in the REM phase (the phase in which we dream) than young people, this occurs at the expense of a reduction in deep (slow-wave) sleep, resulting in more frequent and prolonged awakenings. With age, there is also an increase in diseases and physical problems, which require pharmacological treatments, which can interfere with sleep and aggravate sleeping difficulties. Chronic diseases that frequently appear in the elderly are in themselves one of the most important factors that can affect sleep (painful diseases: arthritis, fibromyalgia, etc.; respiratory diseases: asthma, apnea, etc.).

After speaking of the general patterns of the evolution of sleep throughout the life cycle, we cannot fail to note that circumstances and personal conditions are fundamental. For this reason, we can, and it is not uncommon, to find elderly persons without sleep problems. To prevent these problems, it is very important to have an active life, avoid daytime sleep and a sedentary lifestyle, keeing the night as the only time for sleep and rest. In this way, we can provide a clearer and more distinct sleep-wake cycle.