Not all difficulty sleeping is the same insomnia. Many people toss and turn at night for various reasons, but in most cases they are confused about "whether I have a sleep disorder that needs treatment." In the clinic, distinguishing on your own between temporary insomnia from a few bad nights and chronic insomnia that needs medical evaluation is harder than you might think. In this article, I organize not a method to tame sleep, but how sleep disorders are defined, into what types they are divided, and when care is needed, from a diagnostic perspective. For reference, I too tend to have wide-awake eyes that night if I drink coffee after 5 p.m. Sleep is that sensitive an area for everyone.
Why is sleep so important?
We spend 6 to 8 hours of the day, about one-third of a lifetime, sleeping. The quality of sleep is that much of a key factor governing quality of life. Sleep is not simply rest time but an active process in which the brain and body recover and are tuned up.
Basically, sleep is divided into REM sleep and non-REM sleep. REM sleep is deeply related to dreaming and accounts for about a quarter of total sleep; it is known to be involved in the recovery of memory and intellectual function. Non-REM sleep is divided into light and deep stages and is understood as the stage that restores the physical fatigue accumulated during the day and bodily functions. The two kinds of sleep alternate cyclically through the night, completing a night's recovery.
Appropriate sleep duration varies greatly between individuals. It usually differs from person to person between 4 and 10 hours, and more important than the duration itself is whether you feel refreshed when you wake in the morning and whether fatigue has been recovered during the day. In other words, you should look at "whether you recovered after sleeping" rather than "how many hours you slept."
What is insomnia — first the definition, precisely
Insomnia refers to a state in which, despite sufficient time and environment to sleep, it is difficult to fall asleep or stay asleep, and this causes interference during the day. The International Classification of Sleep Disorders, 3rd edition (ICSD-3) of the American Academy of Sleep Medicine (AASM) defines insomnia along three broad axes.
- Having symptoms of difficulty falling asleep (sleep-onset difficulty), waking during sleep and not falling back asleep (sleep-maintenance difficulty), or waking too early
- That this is so despite being given sufficient time and environment to sleep
- That, as a result, daytime functional decline such as fatigue, reduced concentration, and mood changes accompanies it
The important point here is daytime interference. Even if you slept little at night, if you are fine during the day, it may be different from insomnia in the medical sense. Conversely, if the time spent tossing in bed is long and fatigue, sleepiness, and irritability continue during the day, it may be a signal needing evaluation rather than a simple sleep habit.
Acute and chronic — dividing insomnia by duration
The most practical standard for dividing insomnia is "how long and how often." The AASM's ICSD-3 distinguishes short-term insomnia and chronic insomnia based on the duration over which symptoms have continued.
| Category | Duration | Frequency criterion | Common background |
|---|---|---|---|
| Short-term (acute) insomnia | Less than 3 months | Not fixed | Stress, jet lag, acute illness, environmental change |
| Chronic insomnia | 3 months or more | 3 or more times a week | Chronic stress, hormonal change, comorbid illness |
In the clinic, short-term insomnia with a clear trigger such as an exam, a move, or a breakup, recovering within days to weeks, usually improves naturally. The problem is the case where, even after the trigger is gone, the worry "what if I can't sleep tonight too" calls forth yet more insomnia and hardens into chronic. If it continues 3 or more times a week for over 3 months, rather than enduring on your own, it is better to identify the cause through care.
In the past, insomnia was divided into secondary insomnia stemming from another disease and primary insomnia that is itself independent, but the AASM's latest classification integrated these into a single chronic insomnia. It is a shift in perspective that, even if there is an underlying disease, the insomnia itself must be evaluated and managed together.
Sleep disorders are not only insomnia
Behind the complaint "I can't sleep," various sleep disorders besides insomnia may be hidden. Knowing the definitions and types helps you gauge whether your symptoms are simple insomnia or a state needing other evaluation.
- Daytime sleepiness: Cases where sudden drowsiness pours over you during daily life or unmanageable sleepiness appears. If severe, you can doze even while driving, eating, or walking, with a risk of leading to accidents, and it can also appear as suddenly blanking out.
- Sleep apnea: During sleep, you repeatedly stop breathing and then suddenly snore, in irregular breathing. Often the person does not know and a family member notices first. The oxygen reaching the brain becomes insufficient, so even if you seem to have slept enough, you are not refreshed, leading to daytime sleepiness and fatigue.
- Cataplexy and sleep paralysis: Cataplexy, in which the muscles suddenly lose strength when laughing or getting angry, and sleep paralysis (commonly "being pressed by a ghost"), in which you cannot move even when trying to, when falling asleep or waking, belong here.
- Behavior during sleep: Cases of waking multiple times during sleep, waking to eat something, or experiencing vivid hallucinations around the time of falling asleep.
Because the types are this varied, the approach and tests differ even for the same "sleep problem." For those with large accompanying anxiety and tension, it helps to look together at the pattern in which sleep disorder and anxiety appear together.
Signals that need care — don't put these off
If you have the following symptoms, I recommend not passing them off as a simple sleep habit but consulting a specialist. If even one applies, it becomes a subject for evaluation.
- A state of difficulty falling asleep or frequent waking continues 3 or more times a week for over 3 months
- Even though you seem to have slept enough, you are sleepy during the day to the extent of worrying about accidents while driving or working
- A family member has witnessed snoring or breathing pauses during your sleep
- You get up and walk while asleep, or repeatedly experience frightening hallucinations around the time of falling asleep
- Because of insomnia, your mood, concentration, and daily function clearly decline during the day
In particular, if snoring, breathing pauses, and severe daytime sleepiness suggesting sleep apnea are present together, evaluation is all the more needed, as the cardiovascular burden can grow the longer it is left untended. In fact, the link between chronic insomnia and cardiovascular diseases such as stroke and heart failure is consistently reported. If your sleep problem is dragging on, you may also start lightly with asking about sleep symptoms remotely first.
Women's sleep and hormones — an easily missed cause
Behind the rise in sleep disorders are various factors such as stress, aging, the advance of technology like smartphones, and substance abuse, and for women one more axis is added here — hormonal change. Many people find the quality of their sleep changing through the menstrual cycle, pregnancy, and especially the climacteric.
During the climacteric, as estrogen decreases, hot flashes and night sweats induce mid-night awakening and interfere with sleep maintenance. In clinical experience, it is not uncommon for someone who slept well all their life to suddenly change to a pattern of frequently waking in the early hours around the climacteric. At this time, you should not look at the insomnia alone but evaluate it together with the background of hormonal change to set a direction. Understanding the body changes of the climacteric and their mechanisms gives context for why sleep wavers, and if symptoms are distinct, you can objectively check your hormonal state through menopause screening.
There is a separate article dealing with the climacteric and sleep more concretely, so if insomnia around your 50s is a concern, please also refer to menopausal insomnia and the story of sleep. This article focuses on definition and evaluation, and the lifestyle management for actually taming sleep is explained in more detail there.
In closing — evaluation is the first step
Not every sleepless night is a subject for treatment. But if it continues 3 or more times a week for over 3 months and even shakes your daytime life, that is not a matter of "willpower" but a signal needing evaluation. Since the approach differs depending on whether it is insomnia, another sleep disorder such as sleep apnea, or whether hormonal change is the background, rather than putting off the judgment yourself, it is better to get a check once on an accurate definition. If any of the above symptoms apply, please knock on the door without burden through a remote consultation for sleep concerns. I wish you a comfortable night tonight too.
Written by Lee Dong-hee, Director · OB-GYN specialist · See physician profile
First published November 15, 2023 · Last reviewed May 30, 2026
References: American Academy of Sleep Medicine, ICSD-3 (2014), AASM Clinical Practice Guideline for the Pharmacologic Treatment of Chronic Insomnia in Adults (2017), AASM Clinical Practice Guideline for Diagnostic Testing for Adult Obstructive Sleep Apnea (2017)
This article is intended to provide general health information and does not replace individual diagnosis or treatment. If you have symptoms, please consult through a medical visit.