There's something disappointing about waking up earlier than necessary. It may be nice to doze in and out of sleep in the early morning hours, but it's especially upsetting if you cannot fall back asleep. What might cause someone to wake up before the alarm clock goes off? There are specific conditions, including a fair number of sleep and mood disorders, which might cause early morning awakenings. By understanding these potential causes, you may be able to find a treatment that will keep you asleep until your desired wake time.
The role of insomnia
The primary cause of difficulty staying asleep near morning is insomnia, which is defined as difficulty falling or staying asleep, or sleep that's simply not refreshing. These awakenings may occur throughout the night, but they tend to be more frequent in the second half of the night, due to a diminishing ability to sleep toward the morning hours.
The ability to sleep is linked to two processes, one called the homeostatic sleep drive and the other being the circadian rhythm (which will be discussed more later). The homeostatic sleep drive is the gradual desire for sleep that builds the longer a person stays awake, and relates to the gradual accumulation of a chemical within the brain called adenosine. This "sleepiness signal" eventually helps to initiate sleep; during sleep, it's cleared away so that midway through the night, the desire for sleep is depleted. By morning, it should be completely gone.
If a person awakes during the night — and especially if this awakening occurs toward morning — the ability to return to sleep will be compromised due to the lower levels of adenosine. Sleep may be greatly delayed, fragmented, or disrupted in insomnia, but awakenings near morning can be especially troublesome.
Anxiety and depression may provoke awakenings
Any of the mood disorders, most notably anxiety and depression, can provoke awakenings, which typically occur in the several hours before the intended awakening. For example, if the alarm is set for 6 AM, someone with depression may start waking at 4 AM for no good reason. How can this be addressed?
As with insomnia, it's important to treat the underlying contributing factors that lead to these awakenings. And in the setting of psychiatric distress, these problems can persist, so it's necessary to treat any coexisting depression or anxiety. This may require the use of medications or counseling with the assistance of a psychologist or psychiatrist; in fact, studies have shown that both used in combination are most effective. Insomnia is especially well-treated with cognitive behavioral therapy for insomnia (CBTi).
It's clear that sleep can undermine mood, and conversely, mood problems can greatly affect sleep. By working on both issues together, the complexity of this relationship can be unraveled.
The unexpected influence of sleep apnea
It may seem peculiar to imagine that a breathing disorder such as obstructive sleep apnea may contribute to early morning awakenings. To better understand this relationship, it's necessary to carefully consider the structure of sleep.
It's artificial (but useful) to divide the night in half when considering the stages of sleep. In the first half of the night, slow-wave sleep occurs more frequently, especially among young people. In the second half, rapid eye movement (REM) sleep makes a more frequent appearance. Though the cycles of sleep occur regularly through the night, REM sleep becomes more prolonged towards morning. Therefore, we're more likely to awaken from it near morning and recall the vivid dreams associated with the state.
Sleep apnea is also more likely to occur during REM sleep. The muscles of the body are actively paralyzed during this stage, so we're unable to act out our dreams. (If this does not occur, a condition called REM behavior disorder may result.) Muscles lining the upper airway are also paralyzed, which makes them more collapsible — and collapse manifests as disrupted breathing and sleep apnea. Sleep apnea is often worsened during REM for this reason.
Morning awakenings may therefore occur in the setting of sleep apnea that's worsened during the periods of REM that become more frequent and prolonged towards morning.
Morning larks, Circadian rhythms, and how sleep changes in aging
The last major contributor to early morning awakenings is the class of conditions that are collectively known as circadian rhythm disorders. These include the natural tendency to wake early in the morning (so-called early birds or morning larks), advanced sleep phase syndrome, and natural changes that occur in sleep ability as we get older.
Some people are just naturally morning people: they may prefer to fall asleep earlier (such as at 9 PM) and wake earlier (by 5 or 6 AM). This may be a lifelong preference, and while it isn't necessarily abnormal, it may lead to early morning awakenings. If a sufficient amount of sleep is obtained before getting up for the day, then there's no reason to give it a second thought.
As we get older, our ability to maintain a continuous, uninterrupted period of sleep diminishes. The "machinery" of sleep (whatever we might conceive this to be) isn't working as well as it used to. Sleep may become more fragmented, and there may be more time spent awake in the transition to falling asleep and during the night. Slow-wave sleep diminishes, and total sleep time may be reduced. As part of this, early morning awakenings may occur.
In some cases, a condition called advanced sleep phase syndrome may become apparent. In this circadian rhythm disorder, the onset and offset of sleep moves earlier by several hours. If it's disruptive to social life, it may be treated with the use of properly timed melatonin and light exposure at night.
If you suffer from morning awakenings, you should reflect on your situation and consider what might be contributing to the occurrence. If there's evidence of mood disorders, these should be addressed by a doctor. When a clear explanation cannot be identified, it may be useful to speak with a sleep specialist, who may be able to provide additional insight.