Why do we wake up earlier and earlier as we get older?

The answer to the question of why one wakes up earlier and earlier as one gets older is that it is almost a physiological reaction. As we get older, we need less and less sleep. A baby starts out sleeping approximately 18 hours a day. As we get older, we start shedding hours of sleep; at kindergarten age, children sleep for around nine hours during the night and take a couple of naps during the day, one in the morning and one in the afternoon. These naps also gradually become surplus to the child’s needs. In later life, an adult’s sleep requirement is about eight hours.

As we get older, we sleep fewer hours, but our sleep is also more superficial. Sleep consists of several phases: the shallow sleep stages, which we call N1 and N2, are those that occur when sleep begins; during these phases we go from awake to asleep. Then comes deep sleep, N3, and this is the truly restorative sleep, in which we rest and our brain heals. We call these two periods of shallow and deep sleep non-REM (Rapid Eye Movement). Then there is the REM phase, in which we dream.

As we get older, we spend longer in shallow sleep and less time in deep sleep, and we wake up more frequently. And although we sleep the same number of hours over the course of the day, we get fewer hours of nighttime sleep. Older people take more naps during the day; they may nod off for a bit in the morning and then take a nap in the afternoon. If we add that time to sleep during the night, we reach those eight or nine hours. In addition, many older people go to bed earlier. All of this adds up to them waking up earlier and, in turn, feeling that they are waking up too early in the day.

Another important factor is that, as we get older, our daily activities become fewer, which reduces our need for a good night’s rest. This, of course, applies only if we are talking about the normal physiological reaction in an elderly person who is not suffering from any illnesses. In addition, as we get older, sleep-related pathologies increase. The two most frequent are insomnia and obstructive sleep apnea.

Insomnia occurs when a person is not able to fall asleep, or wakes up frequently or too early, not as a normal physiological reaction of age but as the result of something pathological. If the hours of sleep that a person gets are not sufficient for rest, it is necessary to investigate if there is a problem and, as I say, the most frequent reason is insomnia. The second most frequent cause is sleep apnea, which is respiratory arrest that occurs during the night. As we get older, we make more respiratory pauses during the night and this interrupts our sleep, causing us to wake up, which makes our rest more superficial and less restorative. In the case of women, we are very protected against this pathology before menopause, but after menopause it becomes more frequent.

In any case, returning to the normal physiological response of the human body when we get older, the point is that we usually move from a lifestyle that is hyper-stimulated by work and social interactions, to, for example when we retire, a much more organized life situation in which, generally, we are more respectful of the hours of rest. At that stage, we no longer need longer periods of rest, we sleep well, and when we wake up, we can get up at an appropriate time without needing to stay in bed longer to extend our hours of sleep.

Olga Mediano is a physician specializing in pneumology and sleep researcher at the University Hospital of Guadalajara. This article is part of an initiative sponsored by the Dr. Antoni Esteve Foundation and the L’Oréal-Unesco ‘For Women in Science’ program to answer readers’ questions about science and technology, This question was sent in by Alberto González.

Coordination and editing: Victoria Toro

The advice in this article is of a general nature and is not a substitute for medical consultation. If you have any doubts about a specific issue, contact your doctor or pharmacist.

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