[Doctor Supervised] What causes drowsiness in the evening? Possible illnesses and countermeasures for sleepiness

Do you often feel an intense drowsiness in the evening? This article will discuss the possible causes and related illnesses, as well as introduce countermeasures for drowsiness and recommended items.

Do you ever find yourself overcome by a strong drowsiness in the afternoon, making it hard to concentrate on work or studies? Post-lunch drowsiness can happen to anyone, but if you consistently feel sleepy in the evening, your lifestyle habits or physical condition might be a contributing factor.

Often, the causes are sleep deprivation, blood sugar fluctuations, or brain fatigue. In some cases, sleep disorders like narcolepsy or illnesses like diabetes could also be involved.

This article will delve into the causes of evening drowsiness, potential related illnesses, and effective countermeasures. To improve your daytime performance and enjoy a refreshed evening, be sure to read to the end.

What are the main causes of evening drowsiness?

If you always feel sleepy in the evening, let's start by exploring the causes. Here are six possible factors:

• Sleep deprivation
• Poor sleep quality
• Disrupted body clock
• Blood sugar spikes
• Accumulated stress
• Side effects from medication

Sleep deprivation

Ongoing sleep deprivation significantly impacts daytime performance. The "Sleep Guide for Health Promotion 2023" published by the Ministry of Health, Labour and Welfare recommends 6–8 hours of sleep for adults as a general guideline. However, the appropriate amount of sleep varies depending on an individual's lifestyle, physical condition, and age.

For example, some people feel adequately rested and comfortable during the day with less than 6 hours of sleep, while others might feel unwell without more than 8 hours. The important thing is not to be too fixated on the number of hours, but to listen to your body and find your optimal sleep duration.

The article below provides tips on how to find your ideal sleep duration, so please refer to it:
How much sleep is ideal? How to find and ensure your optimal sleep time

Poor sleep quality

Not just the quantity of sleep, but also its quality, affects both physical and mental health. Even if you get the recommended hours of sleep, poor sleep quality can prevent you from getting adequate rest. If this continues, you may experience intense drowsiness in the afternoon and evening.

Poor sleep quality refers to a state where sufficient deep sleep (slow-wave sleep) is not achieved, often caused by frequent awakenings during the night or environmental factors that disturb sleep.

Therefore, it's not enough to simply sleep more; you must also improve your sleep quality by optimizing your sleep environment.

Disrupted body clock

The human body has an internal clock that operates on an approximately 24-hour cycle, controlling the rhythm of sleep and wakefulness. This body clock plays a role in ensuring our physiological functions operate at appropriate times, adjusting not only the sleep-wake cycle but also body temperature and hormone secretion according to this rhythm.

According to research published in 'Neuroscience Letters | Vol 280,' it is clear that normally, exposure to morning light resets the body clock, and natural drowsiness sets in 15–16 hours later. This is how the body clock works.

However, if you don't get enough light immediately after waking up, your body clock isn't properly reset, causing your bedtime to gradually shift later.

A disrupted body clock can lead to physical ailments such as insomnia, daytime drowsiness, and decreased concentration.
References:
Sleep-Wake Rhythm Disorder｜e-Health Net
Body Clock｜e-Health Net

Blood sugar spikes

A blood sugar spike refers to a rapid increase in blood glucose levels after a meal. Medically, a blood sugar level of 140 mg/dl or higher two hours after eating is defined as a blood sugar spike (postprandial hyperglycemia).

It is more likely to occur when insulin secretion in the body is insufficient or when the secreted insulin does not exert its full effect.

Insulin is a hormone that controls blood sugar levels, but if its function declines, blood sugar levels can rise sharply after meals.

The danger of blood sugar spikes is that they cause continuous damage to blood vessels even with almost no subjective symptoms. If this condition persists, it not only increases the risk of developing diabetes but also the risk of various complications such as heart disease and cerebrovascular disease.

Furthermore, blood sugar spikes often lead to severe drowsiness after meals, as well as unpleasant symptoms like fatigue and headaches.

Reference: Postprandial Hyperglycemia｜e-Health Net

Accumulated stress

Sleep, diet, and exercise are widely recognized as the three pillars of a healthy life, and among them, sleep is closely related to stress.

When we think of stress, we often imagine external pressures such as workplace relationships or work-related burdens. However, insufficient sleep itself can be a significant source of stress.

The causes of stress include:

• Worries about work or relationships
• Worries about caregiving or nursing
• Problems in one's personal life
• Difficulty falling asleep even when trying

When under stress, corticotropin (adrenocorticotropic hormone) is secreted in the brain. This hormone has a sleep-inhibiting effect, which can interfere with quality sleep.

Side effects from medication

Many people have experienced drowsiness after taking medication. Some medications contain ingredients that can cause drowsiness.

Among these, antihistamines, widely used for treating hay fever, are a prime example. Antihistamines primarily work by inhibiting the function of histamine receptors, which cause allergic reactions.

While this action improves allergic symptoms, it also suppresses brain activity. Before taking medication, always check if it contains ingredients that might cause drowsiness.

Major illnesses that can cause evening drowsiness

If you consistently experience evening drowsiness, there might be an underlying medical condition. Here are some possible illnesses:

• Advanced Sleep Phase Syndrome
• Sleep Apnea Syndrome
• Circadian Rhythm Sleep-Wake Disorder
• Narcolepsy
• Mental illnesses such as depression

Advanced Sleep Phase Syndrome

Advanced Sleep Phase Syndrome is a type of sleep disorder where the body's internal clock shifts earlier than usual, leading to drowsiness in the early evening and waking up in the early morning.

As a result, their rhythm may not align with social life, causing disruptions to daytime activities. It is particularly common in the elderly and is believed to have genetic factors involved. A common criterion for diagnosing Advanced Sleep Phase Syndrome is if one falls asleep 2-3 hours before their desired bedtime.

Reference: Delayed (Advanced) Sleep Phase Syndrome｜e-Health Net

Sleep Apnea Syndrome

Sleep Apnea Syndrome is a sleep disorder where breathing temporarily stops during sleep. Breathing stops during sleep, leading to a decrease in blood oxygen concentration.

Due to the drop in oxygen concentration, the body reflexively wakes up and restarts breathing, but the same cycle repeats once the person falls back asleep, making it a dangerous condition.

For example, the heart is excessively burdened to compensate for the lack of oxygen, which results in high blood pressure.

Moreover, chronic low oxygen concentration promotes arteriosclerosis, increasing the risk of myocardial infarction and cerebral infarction. Since symptoms persist throughout the night, deep sleep is not adequately achieved, leading to severe daytime drowsiness.

Reference: Sleep Apnea Syndrome/SAS｜e-Health Net

Circadian Rhythm Sleep-Wake Disorder

The body clock not only regulates the sleep-wake rhythm but also adjusts various physiological functions, such as body temperature changes, hormone secretion, and immune function, on an approximately 24-hour cycle. This is called the circadian rhythm.

Interestingly, the human body clock actually operates on an approximately 25-hour cycle. This means there's about a one-hour discrepancy each day. However, our bodies correct this discrepancy by being exposed to light.

In addition, meal times, exercise, and daily activities such as going to work or school also help regulate the body clock.

However, individuals with circadian rhythm sleep disorder struggle to properly regulate their body clock. As a result, they may not be able to sleep at the appropriate time or experience severe drowsiness at the time they should be awake, causing persistent disruption to their daily lives.

Reference: Circadian Rhythm Sleep Disorder｜e-Health Net

Narcolepsy

Narcolepsy refers to a sleep disorder characterized by intense daytime sleepiness or sudden, irresistible sleep attacks. There is an abnormality in the brain's function of maintaining wakefulness, leading to overwhelming sleepiness or suddenly falling asleep during the day, even after getting sufficient sleep.

Examples of symptoms include:

• Sudden loss of muscle tone
• Falling asleep during an important meeting
• Experiencing hallucinations when falling asleep
• Feeling paralyzed, like in sleep paralysis

Narcolepsy is believed to be caused by a deficiency of orexin, a protein in the brain that regulates wakefulness.

For more detailed information about narcolepsy, please refer to the article below:
What is Narcolepsy? Causes, Symptoms, and Characteristics of Those Prone to It

Mental illnesses such as depression

There is a close relationship between depression and sleep disorders, with many depression patients experiencing poor quality sleep.

Characteristic symptoms of depression include:

• Persistent difficulty falling asleep (insomnia)
• Waking up multiple times during the night (middle-of-the-night awakenings)
• Waking up early in the morning (early morning awakening)

Early morning awakening, in particular, is a characteristic symptom of depression and serves as a key indicator for diagnosis.

Furthermore, in patients with depression, deep sleep (slow-wave sleep) tends to decrease, leading to an overall lighter sleep. Many patients also report frequent nightmares.

Severe fatigue upon waking can significantly impair a patient's quality of life (QOL), so it must be addressed. Additionally, persistent difficulty falling asleep can disrupt the sleep-wake rhythm, sometimes leading to a reversal of day and night.

If you want to know more about middle-of-the-night awakenings, please refer to the article below:
【Physician Supervised】What is Middle-of-the-Night Awakening? Causes and Cures for Waking Up Multiple Times at Night

5 ways to avoid evening drowsiness

To avoid feeling drowsy in the evening, try the five methods described below:

• Consume caffeine
• Do stretching exercises
• Press acupressure points
• Take a nap
• Consult a medical institution

Consume caffeine

The accumulation of sleep-inducing substances in the brain is a natural mechanism that causes drowsiness. Caffeine temporarily suppresses the action of these sleep-inducing substances, thereby exerting an awakening effect. The stimulating effect of caffeine lasts for 5 to 8 hours, and it can take several days for it to be completely eliminated from the body.

It is especially important to note that the half-life of caffeine is approximately 4 hours. The half-life is the time it takes for the concentration of a substance in the body to be reduced by half. To ensure quality sleep, it is recommended to avoid caffeine intake 4 hours before bedtime, taking into account its half-life.

While many people associate caffeine primarily with coffee, it's important to remember that other beverages also contain it.

Reference: Caffeine and Sleep｜NCNP Hospital National Center of Neurology and Psychiatry

Excessive caffeine intake can not only impair sleep quality but also cause problems such as insomnia and anxiety, so it's important to pay attention to appropriate amounts and timing of intake. Additionally, the article below further explains the upper limits of caffeine intake. Please refer to it.

How are sleep and caffeine related? What is the upper limit of caffeine intake?

Do stretching exercises

When you feel intense drowsiness in the evening, it might be because your parasympathetic nervous system is dominant. To alleviate drowsiness, it's necessary to activate the sympathetic nervous system, and physical activity is an effective way to do this.

Here are some stretches you can easily do at work or at home. Please try them:

1. Straighten your back in a relaxed posture.
2. Clasp both hands and stretch them high above your head, pushing your palms towards the ceiling.
3. Extend your right arm across your chest.
4. Repeat with the other side.

The trick is to stretch slowly while exhaling. Repeating this a few times will promote blood circulation and help suppress drowsiness.

Doing this during desk work breaks can not only help with drowsiness but also prevent shoulder stiffness.

Press acupressure points

In Oriental medicine, there are said to be 361 acupressure points on the body, and several of them are effective in suppressing drowsiness.

Stimulating the following key acupressure points is recommended for awakening from drowsiness:

Jingming (睛明)

Jingming (睛明) is an acupressure point located in the inner corner of the eye. Gently pressing it with the pad of your thumb can relieve eye fatigue and suppress drowsiness. Since the skin is delicate, avoid pressing too hard.

Taiyang (太陽)

Taiyang (太陽) is an acupressure point located on the temple. Gently pressing it with your middle finger can relieve eye and head fatigue and promote alertness.

Fengchi (風池)

Fengchi (風池) is a depression located behind the neck and below the ear. Gently pressing and massaging both sides simultaneously with the thumbs of both hands can relax neck tension and clear the head.

Baihui (百会)

Baihui (百会) is a slightly indented acupressure point located at the top of the head. Gently massaging it in a circular motion with your fingertips can relieve stress and insomnia.

Hegu (合谷)

Hegu (合谷) is the area at the base of the thumb and index finger. Pressing it with the thumb of the opposite hand can stabilize one's mental state and alleviate neck and shoulder stiffness.

The key is to stimulate these acupressure points gently for about 3 to 5 seconds each time. Be careful not to press too hard.

Take a nap

While naps can improve work efficiency, naps longer than 60 minutes can lead to entering a deeper sleep stage, which paradoxically causes more intense drowsiness upon waking.

An effective way to solve this problem is to consume caffeine before taking a nap.

Since caffeine's stimulating effects begin to appear about 30 minutes after ingestion, taking caffeine before a nap can align the waking moment from the nap with the onset of caffeine's alerting effect, thereby helping to combat drowsiness.

Reference: Caffeine Intake in Daily Life - Mechanism of Action and Safety Evaluation -｜Hisashi Kurihara

This method is especially recommended for those who work shift duties.

Additionally, we introduce other ways to alleviate drowsiness below. Please take a look:
【Physician Supervised】12 Ways to Instantly Wake Up! How to Deal with Drowsiness in an Instant

Consult a medical institution

If you have tried the drowsiness countermeasures described above and still experience severe evening drowsiness, you might be dealing with conditions such as sleep apnea syndrome, circadian rhythm sleep-wake disorder, or depression.

Persistent drowsiness may indicate a condition requiring specialized treatment. For your health, we recommend consulting a medical institution such as a sleep clinic or psychiatrist. Appropriate diagnosis and treatment by a specialist can lead to an improvement in symptoms.

Improve sleep quality with bedding! Brain Sleep items

Evening drowsiness is often caused by poor sleep quality. To ensure a good night's sleep, choosing the right bedding for you is essential. Here, we introduce Brain Sleep products.

Additionally, we also discuss other methods to enhance sleep quality below, so please refer to them:
What is the secret to improving sleep quality? Understanding what determines quality and causes of poor sleep

Brain Sleep Pillow

The Brain Sleep Pillow is a personalized pillow tailored to the shape of your head and sleeping posture. More than 90% of its structure consists of an air layer, allowing it to release heat and moisture generated during sleep, thereby maintaining a comfortable sleeping environment.

Experiments showed that 6 hours of sleep with this pillow resulted in 16% higher fatigue recovery compared to 7 hours of sleep with a typical functional pillow.
Click here for more details on the Brain Sleep Pillow

Brain Sleep Mattress Premium Float

The Brain Sleep Mattress Premium Float replicates NASA's proposed neutral posture with its unique three-dimensional structure, allowing you to experience a sensation as if floating.

Optimal firmness is felt at the shoulders, hips, and legs, enabling an ideal relaxed posture free from gravity. Its 9-layer structure absorbs and rebounds in response to body movements during sleep, reducing energy consumption and supporting comfortable sleep until morning.
Click here for more details on the Brain Sleep Mattress Premium Float

Brain Sleep Comforter All Seasons

This product incorporates temperature-regulating material developed from space suit technology. It can be used as a single layer in spring, summer, and autumn, and as an inner blanket in winter.

Its automatic temperature control function maintains a comfortable sleeping temperature throughout the year, promoting deep sleep. Furthermore, it is a convenient bedding item that can be machine-washed and folded compactly for storage.
Click here for more details on the Brain Sleep Comforter All Seasons

Brain Sleep Coin

Based on data from the latest sleep research, we have developed a unique measurement algorithm to analyze individual sleep patterns more accurately. We have created an innovative system that improves sleep quality, converts good quality sleep into coins, and allows them to be exchanged for various benefits and services.

Through the collaboration between devices and applications, we offer an unprecedented new experience.
Click here for more details on Brain Sleep Coin

Brain Sleep Recovery Wear

This sleep-specialized wear supports body conditioning just by wearing it. It enables effective maintenance even with limited sleep time, allowing you to recharge energy for the next day.

With generously designed armholes and minimal constrictions from elastic or ribbing, its relaxed silhouette provides comfortable wear that doesn't hinder natural turning during sleep.
Click here for more details on Brain Sleep Recovery Wear

Understand the causes and countermeasures for evening drowsiness to live healthily

Evening drowsiness can be linked to various factors such as lack of sleep, poor sleep quality, stress, disrupted circadian rhythms, and sleep apnea syndrome.

Addressing these issues requires taking measures like maintaining a regular lifestyle and alleviating stress. Additionally, re-evaluating your sleep environment is crucial for achieving quality sleep.

Brain Sleep offers a wide range of products developed based on scientific research. With an extensive lineup including pillows, mattresses, and wear, we support higher quality sleep.

For details on each product, please see this page:
Brain Sleep product list