Why Am I Waking up at the Same Time Every Night?
Medically reviewed by Kashif J. Piracha, MD
Waking up at the same time every night can be caused by many things. It may be influenced by when you fall asleep at night and the normal circadian rhythms that regulate the sleep-wake cycle. In short, by falling asleep early, your "internal clock" may be set to wakefulness while it is still dark.
Other factors can cause you to awaken regularly at night, such as stress, temperature, sleep habits, and medical conditions like sleep apnea. Over time, these sleep patterns can affect your health and require medical treatment and/or improvements in your sleep hygiene,
This article explains how sleep timing, circadian rhythms, and sleep cycles contribute to routine nighttime awakenings. It also describes other factors that can influence your waking habits.
Sleep Timing
If you wake up at the same time in the morning or at the same time in the middle of the night, it may be because you go to sleep at roughly the same time every night.
For instance, if your body naturally wakes up after six hours, and you always go to bed at 10:00 p.m., you might expect to wake at 4:00 a.m. nearly every day.
Many people who awaken at the same time every night don't even realize it. That's because there is a stage between sleep and wakefulness when you may not be completely aware of what's going on around you.
In such cases, you might awaken, roll over, and fall back to sleep. If you don’t check the clock, you might not even realize that you've been awake. During a short awakening, you might only experience a strong desire to get back to sleep.
Circadian Rhythm
The circadian rhythm is an internal clock that regulates the sleep-wake cycle. It operates on a 24-hour cycle, regulated by a part of the brain called the suprachiasmatic nucleus. In addition to influencing sleep and wake patterns, the circadian rhythm also maintains your core body temperature and the release of hormones that regulate growth, metabolism, and circulation.
The circadian rhythm is largely "synched" to sunrise and sunset. During sunrise, light passing through the translucent skin of the eyelids triggers biological changes that cause you to awaken.
But awakenings can happen even if you're wearing an eyemask or live in parts of the northern hemisphere where the sun rises late. This is because the circadian rhythm wants the body to remain on a set schedule so that certain vital patterns (like the release of hormones) are consistent.
This includes waking up before dawn if your circadian clock has been "set" to follow this sleep-wake pattern.
Sleep Cycles and Stages
Sleep has a structure and pattern, sometimes referred to as sleep architecture. Each night unfolds with regularity, although there can be variations now and then.
There are two categories of sleep stages:
Non-rapid eye movement (NREM): This is the cycle that progresses from stage 1 (wake/sleep transition) to stage 2 (light sleep) to stage 3 (deep sleep).
Rapid eye movement (REM): This is when most people dream. During this stage, your body limits your ability to move your limbs by temporarily "paralyzing" the somatic (voluntary) nervous system.
As a general rule, sleep progresses from wakefulness through the lighter to deeper states of sleep and back. Approximately every 90 to 120 minutes, REM sleep occurs.
At the end of REM, you may briefly awaken as the sleep stages reset. This can be a routine event that you may remember or have no recollection of.
Other Contributing Factors
Some other factors may be influencing your consistent nighttime awakenings. Because you may be half awake/half asleep when this happens, you may have no recollection of why they occurred—only that they occurred.
Environment
Environmental noise is a common cause of nighttime awakenings. If you live near a train track, for instance, a train that passes every night at the same time may cause you to awaken without you even knowing it. Even things like heaters and air conditioners that go on and off can cause stirrings.
Temperature can also play a part. In winter, temperatures can gradually fall overnight, causing you to awaken in the middle of the night to cover yourself. The opposite may be true if you are covered with a heavy blanket and make it a habit of kicking it off every night.
Digital Devices
Electronic devices can overstimulate your nervous system and make it harder to fall asleep. But they can also interrupt your sleep due to low-level humming or light emission.
For example, your eye might perceive light from the LED display as you roll over in bed (especially if it is flashing). There is evidence that certain low-level electronic sounds can alter N-REM sleep and delay or interrupt the transition from sleep stages 1 to 2.
Stress-Related Insomnia
Stress is a major contributing factor to insomnia and one that can cause recurrent nighttime awakenings due in part to elevations in blood pressure. This is especially true if a person has an anxiety disorder, in which stress levels can remain consistently high.
Spikes in blood pressure during sleep, called hormonal hypertension, can cause a cascade of symptoms that can interfere with sleep, including rapid heartbeats, a sudden urge to urinate, and sleep apnea.
Sleep Disorders
Sleep apnea happens when a person's breathing stops or is interrupted during sleep, sometimes hundreds of times throughout the night. When the gaps in breathing are prolonged, it is not unusual to awaken abruptly with a choking sensation.
Sleep paralysis, an uncommon sleep disorder, is a feeling of being conscious but unable to move. It occurs when a person passes between stages of wakefulness and sleep. The sensation can be terrifying and cause a person to jolt awake in the middle of the night.
Nocturia
Nocturia is the term used to describe the need to urinate at night, sometimes repeatedly. Conditions that cause nocturia include:
Excessive intake of water
Sleep apnea
Nocturia may be a sign of a serious medical condition in need of treatment and should not be ignored.
Digestive Problems
Conditions like gastroesophageal reflux disease (GERD), hiatal hernia, and gastritis can cause routine awakenings at night because the position of your body and head can trigger symptoms.
With hiatal hernia, turning on your side and pulling your knees to your chest can cause the esophagus (feeding tube) to bulge into the chest cavity, triggering reflux.
With GERD and gastritis, laying on your back with your head flat can allow stomach acid to leak into the esophagus, causing heartburn.
Hormonal Changes
Changes during menopause can cause you to have hot flashes and night sweats. Insomnia is a common system of menopause caused by declines in estrogen which affects a person's ability to achieve deep sleep.
Hormonal changes during pregnancy can strange dreams that interfere with sleep, while physical changes in the third trimester can affect sleep due to back pain, nocturia, leg cramps, heartburn, and fetal movements.
Aging
Older adults have an increased risk of sleep disorders including insomnia, sleep apnea, restless legs syndrome, and circadian rhythm disturbances. As many as 50% complain about sleep problems.
Several changes occur in both sleep architecture and sleep timing throughout a lifespan. Among them, aging is associated with a decrease in the sensitivity of the suprachiasmatic nucleus which regulates the circadian rhythm.
A significant percentage of older adults have multiple chronic conditions like heart disease, diabetes, and GERD that contribute to sleep disturbances at night. Structural changes in the upper respiratory tract and the increased incidence of respiratory diseases can contribute to or worsen sleep apnea.
Medications
Many drugs, both over-the-counter and prescription, can interfere with sleep and lead to nighttime awakenings:
ACE inhibitors can cause dry mouth and muscle aches that awaken you at night.
Alpha blockers like Flomax (tamsulosin) can decrease REM sleep and promote urination.
Antidepressants like Prozac (fluoxetine) and Effexor (venlafaxine) can disrupt REM sleep.
Bronchodilators like albuterol that can cause palpitations and excitability.
Caffeine can overstimulate the nervous system and cause palpitations.
Corticosteroids (steroids) like prednisone can affect melatonin levels and sleep cycles.
Decongestants like Sudafed (pseudoephedrine) can cause excitability.
Diuretics ("water pills") can promote nighttime urination.
Opioids like hydrocodone and oxycodone can cause sleep-disordered breathing.
Summary
Your body has internal mechanisms for timing your sleep patterns, called the circadian rhythm. Disruption of this function can cause you to wake up at night.
There are numerous reasons why this may occur. Poor sleep hygiene, noise, temperature, stress, illness, sleep disorders, medications, and digital devices can all cause nighttime awakenings. Even aging can cause biological and physiological changes that cause sleep interruptions.
Read the original article on Verywell Health.
