Why you wake up at night and can't go back to sleep - 7 common causes and what you can do

3 AM. You're awake, staring at the ceiling, feeling that familiar frustration – your body is tired, but your mind won't shut down.
Or maybe you fall asleep easily but wake up after 4-5 hours and can't get back to sleep. The day ahead will be tough.

If this happens frequently, it's not bad luck or "just how you're built." In most cases, there are concrete causes – and many of them can be influenced without medication.

In this article, we don't promise miraculous solutions. Instead, we offer an honest look at the most common reasons why sleep is interrupted and what you can realistically do.

1. Body and bed temperature

The human body follows a thermal cycle throughout the night. To fall asleep and stay asleep, the ambient temperature needs to drop slightly – by about 1-2 degrees Celsius compared to daytime temperature. If your bed, mattress, or bedding retains heat, your body can't make this transition, and sleep becomes shallow or interrupted.

Studies published in the journal Sleep Medicine Reviews show that the ideal ambient temperature for sleep is between 16°C and 19°C for most adults. Bedding matters immensely: synthetic materials or those with a very high thread count retain heat and moisture, disturbing sleep, especially in warmer months.

What you can do: Opt for natural fiber bedding – cotton, linen, or hemp. These regulate temperature more efficiently than synthetic materials, absorbing moisture and allowing air to circulate. A cool room and "breathable" bedding are two of the most effective and accessible interventions for continuous sleep.

2. Sleep position and inadequate body support

Many people wake up at night without knowing why – and the cause is purely mechanical. When the body lacks adequate support for the spine, hips, or shoulders, muscles remain tense to compensate. At some point, the accumulated tension causes an awakening.

This is more common in people who sleep on their side – the most common sleep position for adults. Without proper support between the knees or for the lumbar region, the spine remains slightly twisted for hours, which can lead to back, hip, or shoulder pain and, implicitly, fragmented sleep.

What you can do: A body pillow placed between the knees, or one that gently hugs the torso, can align the spine and eliminate nocturnal muscle tension. It's not a gadget – it's a solution with simple biomechanical logic. If you sleep on your back, a pillow under your knees reduces lumbar pressure. If you are over 50 or have a sedentary job, it's worth paying attention to this aspect before any other intervention.

3. Elevated cortisol levels in the evening

Cortisol is the stress hormone, but also a natural regulator of the circadian rhythm. Normally, its level is high in the morning (to wake you up and activate you) and gradually decreases towards evening, making way for melatonin.

The problem arises when chronic stress, irregular schedules, or excessive artificial light in the evening keep cortisol levels high at night. The result: you have difficulty falling asleep or wake up abruptly in the first part of the night, with an unjustified state of alertness.

According to a study published in Psychoneuroendocrinology, people with elevated evening cortisol levels report significantly more nocturnal awakenings and poorer REM sleep quality compared to those with a normal cortisol profile.

What you can do: Your evening routine matters more than many people think. Reducing stimuli (news, email, tense discussions) 60-90 minutes before bed, a lower room temperature, and warm light genuinely contribute to lowering cortisol. Intense physical exercise after 7:00 PM can, paradoxically, keep cortisol levels high until late – something to keep in mind if evening workouts are part of your routine.

4. Mild or undiagnosed sleep apnea

Obstructive sleep apnea means that breathing stops partially or completely for a few seconds, dozens or hundreds of times a night. Severe forms are usually noticed by a partner (loud snoring, breathing pauses). But mild forms can go unnoticed for years.

Subtle symptoms include: frequent awakenings for no apparent reason, feeling unrested even after 8 hours of sleep, morning headaches, dry mouth upon waking, and daytime sleepiness.

Mild apnea affects approximately 10-15% of adults, according to data from the American Journal of Respiratory and Critical Care Medicine, and a large portion remains undiagnosed.

What you can do: If you identify with several of the symptoms above, a consultation with a sleep specialist (somnologist) or a polysomnography test can clarify the situation. It's not a minor problem – untreated apnea is associated with an increased long-term cardiovascular risk. Sleeping on your side (instead of on your back) reduces the frequency of episodes in mild forms.

5. Magnesium deficiency

Magnesium is involved in over 300 biochemical reactions in the body, including regulating the nervous system and sleep. Its deficiency is more common than one might think – the modern diet, rich in processed foods and poor in green vegetables, nuts, and seeds, contributes to insufficient intake at the population level.

Magnesium activates GABA receptors in the brain – the calming neurotransmitter, essential for the transition to sleep. Low magnesium levels can lead to a more reactive nervous system, with more frequent awakenings and shallower sleep.

A study published in the Journal of Research in Medical Sciences on a group of elderly adults showed that magnesium supplementation significantly improved sleep quality, sleep onset latency, and sleep duration compared to the placebo group.

What you can do: Before resorting to supplements, try to increase dietary intake: pumpkin seeds, almonds, spinach, black beans, dark chocolate (over 70%). If you feel that the deficiency is real (muscle cramps, anxiety, chronic fatigue), discuss supplementation with your doctor – magnesium glycinate or malate are forms with better absorption and milder digestive effects compared to magnesium oxide.

6. Exposure to blue light before bed

Human eyes contain specialized cells (melanopsin-containing ganglion cells) extremely sensitive to blue light – the dominant wavelength in phone, tablet, and laptop screens. These cells transmit signals directly to the pineal gland, inhibiting melatonin production.

A meta-analysis published in Chronobiology International calculated that exposure to screens for 2 hours before bed can reduce melatonin levels by up to 22% and delay sleep onset by 10-30 minutes. In the long run, this shifts the circadian rhythm and makes nocturnal awakenings more frequent.

What you can do: Reducing screen time 60 minutes before bed is the most effective step – more effective than blue light filters or specialized glasses, according to the same studies. If this is not realistic, activate night mode on devices (which shifts the tone towards yellow-orange) and minimize brightness. Reading on paper or a quiet conversation before sleep remain difficult to replace.

7. The wrong pillow for your sleep style

This is perhaps the most overlooked factor, precisely because it seems minor. But a pillow that is too high, too hard, or too soft for your sleep position keeps your neck in forced flexion or extension all night. Your cervical muscles become fatigued, and your body generates awakening impulses to readjust its position.

Additionally, pillows made of synthetic materials that retain heat contribute to local overheating – another factor for nocturnal awakening, discussed above.

There is no universal pillow. It depends on your weight, shoulder width, preferred sleep position, and individual sensitivities. What works for one person may be completely unsuitable for another.

What you can do: If you wake up with a stiff neck or shoulders, or if you frequently change positions in your sleep without realizing it, it's worth re-evaluating your pillow. Natural materials (cotton, adjustable filling) have the advantage of being adaptable and not retaining heat. A body pillow can be an effective complementary solution for side sleepers – it reduces the need for readjustment and maintains spinal alignment without conscious effort.

What we haven't included in this list – and why

Dozens of factors can influence sleep: alcohol (which fragments REM sleep even if it speeds up falling asleep), caffeine consumed in the afternoon, certain medications, clinical anxiety, or depression. We haven't included them not because they are less important, but because they are better documented in public awareness or require direct medical intervention.

The seven factors above are relevant precisely because they are frequently overlooked, can be influenced without a prescription, and produce visible results relatively quickly.

A word about realistic expectations

Sleep is a complex system, and there is no single intervention that solves everything. If problems persist for more than a few weeks, regardless of the changes you make, medical consultation remains the best next step. Somnology is a recognized medical specialty, and there are sleep clinics in major cities in Romania.

But if you're at the stage where your sleep is simply worse than it should be – without a major medical cause – a few adjustments to your sleep environment, evening routine, and physical equipment (bedding, pillow, temperature) can make a surprisingly big difference.

At Voinicel.ro, we have been producing body pillows and natural material bedding – cotton, linen, hemp – for over 15 years. We don't claim that a pillow solves all sleep problems. But if position or temperature are among your causes, explore our collection – all products are custom-made from quality, natural materials.