Daytime Sleep: Why Can't I Sleep At Night?

There are many reasons why someone might be only able to sleep during the day. One of the most common reasons is a Circadian Rhythm Sleep Disorder, which occurs when the circadian clock in the brain is not synchronized with local time, resulting in abnormal sleep patterns. This can include jet lag, shift work adjustments, delayed sleep phase syndrome, and advanced sleep phase syndrome. Other reasons for daytime sleepiness include sleep disorders such as insomnia, sleep apnea, restless leg syndrome, hypersomnia, and parasomnia. Lifestyle choices such as caffeine and alcohol consumption, irregular schedules, and aging can also contribute to sleep problems.

Circadian Rhythm Disorders

Circadian rhythm sleep disorders occur when the circadian clock in the brain, which drives daily behavioural and physiological rhythms, is not synchronised with 'real' local time. This can result in abnormal sleep patterns, sleep loss, and fatigue.

The circadian rhythm is like an internal timekeeper for everything our bodies do in a 24-hour period. This system uses light, dark, and our biological clock to regulate body temperature, metabolism, hormones (including melatonin), and sleep.

The body's master clock is called the suprachiasmatic nucleus (SCN). Located in the brain, the SCN controls melatonin production. This hormone helps regulate sleep. During the day when it's light outside, melatonin levels remain low. Later in the day, as it grows darker, our bodies produce more melatonin, with levels peaking between 2 and 4 a.m. before falling again. Our bodies are best primed for sleep about two hours after melatonin levels start to rise.

There are several types of circadian rhythm sleep disorders, including:

• Delayed Sleep Phase Disorder: This occurs when an individual's preferred time for sleep is typically after 2 a.m., with a wake-up time after 10 a.m. This results in difficulty falling asleep and waking up at times conducive to school and work. This condition is most common in adolescents.
• Advanced Sleep Phase Disorder: This is more common in older adults, who may prefer to go to bed early in the evening (6 p.m. to 9 p.m.) and wake up in the early morning hours (2 a.m. to 5 a.m.). This makes it difficult to stay awake through the evening hours.
• Irregular Sleep Wake Disorder: This disorder is characterised by a lack of rhythm in a person's sleep and wake cycle. Sleep occurs irregularly throughout a 24-hour period, with individuals unable to sleep through the night and experiencing difficulty maintaining wakefulness during the day. This disorder is commonly seen in elderly patients with dementia.
• Free-running disorder or non-24-hour sleep-wake disorder: This rare disorder is more commonly seen in individuals with blindness. Bright morning light (sunrise) helps align our internal clock to the 24-hour day. When light perception is absent, the sleep period drifts later and later each day, causing this disorder.
• Jet Lag: This occurs during air travel when we traverse time zones faster than our body clocks can adjust, resulting in a mismatch between preferred and destination sleep and waking times.
• Shift Work Sleep Disorder: This disorder is due to an unconventional work schedule that causes individuals to remain awake during their preferred sleep times. As a result, they experience sleepiness while at work and insomnia during the time available for sleep. Other symptoms may include difficulty concentrating, headaches, and low energy levels while awake.

Sleep Disorders

There are several reasons why someone might only be able to sleep during the day. One common reason is a condition called hypersomnia, which is characterised by extreme daytime sleepiness despite getting an adequate amount of nighttime sleep. People with hypersomnia may sleep for long periods and wake up feeling confused or irritable, a condition known as sleep inertia. This condition affects about 5% of the population, with an average onset age of 17 to 24 years.

Another reason could be a circadian rhythm sleep disorder, where the circadian clock in the brain that drives daily behavioural and physiological rhythms is not synchronised with 'real' local time. This can result in abnormal sleep patterns, sleep loss, and fatigue. One type of circadian rhythm sleep disorder is Delayed Sleep Phase Disorder (DSPD), where individuals are unable to fall asleep until the early morning, typically between 2 am and 6 am, and sleep correspondingly longer during the daytime. DSPD is more common in adolescents, affecting about 7 to 16% of young people and 1% of adults.

Other potential causes of daytime sleepiness include anxiety, depression, insomnia, medication, alcohol consumption, caffeine intake, and diet. In some cases, daytime sleepiness may be a symptom of an underlying medical condition such as epilepsy, hypothyroidism, encephalitis, multiple sclerosis, or Parkinson's disease.

If you are experiencing excessive daytime sleepiness, it is important to consult a healthcare professional for proper diagnosis and treatment.

Hypersomnia

There are several types of hypersomnia sleep disorders:

• Idiopathic hypersomnia: People with this type sleep for long periods and wake up feeling confused, irritable, or not refreshed (sleep inertia). There is no known cause for this type of hypersomnia.
• Narcolepsy type 1 (with cataplexy): This type is characterised by sudden attacks of sleep and a loss of muscle control (cataplexy).
• Narcolepsy type 2 (without cataplexy): Similar to type 1, but without the loss of muscle control.
• Kleine-Levin syndrome (KLS): This type is characterised by excessive sleepiness and may be related to hormonal changes, particularly in menstrual cycles.
• Hypersomnia associated with other disorders: Hypersomnia can also occur in conjunction with other disorders, such as narcolepsy.

Circadian rhythm sleep disorders are another type of sleep disorder that can cause abnormal sleep patterns. These disorders occur when the internal circadian clock, which regulates the 24-hour cycle of sleep and wakefulness, is disrupted. This can lead to problems falling asleep at the desired time, staying asleep, and feeling rested during the day.

If you suspect you may have hypersomnia, it is recommended to consult a healthcare professional. They may ask about your sleep patterns, mental and physical health, and any medications you are taking. Keeping a sleep diary can also be helpful in identifying any patterns or issues. Treatment for hypersomnia depends on the underlying cause and may include medications to promote wakefulness.

Sleep Inertia

There are three main theories explaining sleep inertia. The first theory suggests that it is caused by an increase in delta waves in the posterior part of the brain. Delta waves, or slow waves, are commonly observed during the non-rapid eye movement (NREM) stage of sleep, and they are more likely to increase after periods of sleep deprivation or loss. Sleep inertia may occur when the brain has not yet reduced delta waves in preparation for waking up or when an individual is suddenly awoken during NREM sleep.

The second theory focuses on adenosine, a nucleic acid compound found in the brain that plays a crucial role in sleep and wakefulness. Upon waking, adenosine levels should be low. However, research indicates that sleep inertia could be caused by high levels of adenosine upon awakening. Adenosine levels in the brain progressively increase with sleep deprivation and return to normal during sleep. Therefore, when an individual wakes up after a period of sleep deprivation, high amounts of adenosine will be bound to receptors in the brain, leading to a slowdown in neural activity and a feeling of tiredness.

The third theory relates to the body's blood flow to the brain, which follows a pattern that corresponds to sleep cycles. Chronic fatigue syndrome (CFS) is associated with reduced cerebral blood flow, and its symptoms resemble those of sleep inertia. It is possible that a reduction in blood flow upon waking contributes to the symptoms of sleep inertia. However, more research is needed to confirm this theory.

Certain factors can influence the duration and severity of sleep inertia. For example, night shift workers who take an hour-long nap during the early morning hours tend to experience longer periods of sleep inertia. This is due to the strong drive for sleep at that time and the fact that a longer nap allows the brain to enter deeper stages of sleep. Caffeine consumption before a short nap or immediately upon waking can help reduce the duration of sleep inertia by increasing alertness and attentiveness. Additionally, exposure to bright light and washing the face have been found to restore alertness more quickly after a nap.

Sleep Hygiene

Set a Sleep Schedule

Having a set sleep schedule is important for normalising sleep as an essential part of your day. It helps your brain and body get accustomed to getting a full night's sleep. Here are some ways to improve your sleep schedule:

• Fixed Wake-Up Time: Try to wake up at the same time every day, even on weekends. A fluctuating schedule disrupts your body's sleep rhythm.
• Prioritise Sleep: Avoid skipping sleep for work, studies, socialising, or exercise. Calculate a target bedtime that allows for 7-8 hours of sleep and prepare for bed around that time each night.
• Make Gradual Adjustments: If you want to shift your sleep times, do it gradually. Making sudden changes can disrupt your sleep schedule. Adjust your sleep times by up to an hour or two each day until you reach your desired bedtime.
• Manage Naps: Naps can be energising, but they can also disrupt your nighttime sleep. Keep naps short and limited to the early afternoon.

Follow a Nightly Routine

Your pre-sleep routine can help you relax and prepare for sleep. Here are some tips for an effective nightly routine:

• Consistency: Follow the same steps each night, such as putting on pyjamas and brushing your teeth. This reinforces the signal to your mind and body that it's bedtime.
• Wind Down: Allocate 30 minutes before bed for calming activities like soft music, light stretching, reading, or relaxation exercises.
• Dim Lights: Bright lights can hinder melatonin production, a hormone that facilitates sleep. Dim the lights an hour before bedtime to encourage melatonin production.
• Unplug from Electronics: Blue light from electronic devices can suppress melatonin production and keep your brain alert. Avoid screens for 30-60 minutes before bed to improve sleep quality.
• Practise Relaxation Techniques: Instead of forcing yourself to fall asleep, focus on relaxation. Meditation, mindfulness, paced breathing, and other relaxation techniques can help prepare your mind and body for sleep.

Cultivate Healthy Daily Habits

Your daytime habits also play a crucial role in supporting your sleep. Here are some daily habits to improve your sleep hygiene:

• Daylight Exposure: Light, especially natural sunlight, is a key regulator of your body's circadian rhythm. Get at least 30 minutes of natural light exposure daily to encourage quality sleep.
• Regular Exercise: Regular physical activity can improve your sleep quality and overall health. However, avoid intense exercise close to bedtime, as it may hinder your body's ability to settle down for sleep.
• Reduce Stimulants: Stimulants like nicotine and caffeine disrupt sleep. Avoid nicotine entirely, and limit caffeine intake after 2 PM or earlier, depending on your sensitivity.
• Limit Alcohol Consumption: Alcohol may make you drowsy initially but can disrupt sleep later in the night. Moderate your alcohol intake and avoid it a few hours before bedtime.
• Avoid Late Dinners: Eating a large meal close to bedtime can negatively impact your sleep quality and cause acid reflux. Eat dinner a few hours before bed, and opt for lighter snacks if you need an evening bite.

Optimise Your Bedroom Environment

Your sleep environment should be calm and free of disruptions. Here are some tips to create a sleep-friendly bedroom:

• Comfortable Bedding: Invest in a comfortable mattress, pillows, and bedding. A supportive mattress and pillow ensure proper spinal alignment and pain-free sleep. Choose bedding that feels comfortable and maintains a pleasant temperature.
• Ideal Temperature: Set your bedroom temperature to a cool yet comfortable level, typically between 60-68°F (15.6-20°C).
• Block Out Light: Use heavy curtains or an eye mask to block out light and prevent interruptions to your sleep.
• Reduce Noise: Use earplugs, a white noise machine, or a fan to minimise noise disturbances.
• Calming Scents: Light scents like lavender may induce a calmer state of mind and create a positive sleep environment.

Frequently asked questions