Daytime Sleep And Sickness: What's The Link?

Feeling unwell after a nap can be caused by a variety of factors, including the duration of the nap, your sleeping position, and underlying health conditions. Longer naps, for instance, increase the likelihood of sleep inertia and acid reflux, resulting in feelings of grogginess, nausea, or heartburn. Sleep is essential for recovery when you're sick, but napping during the day can sometimes leave you feeling worse, especially if you're prone to acid reflux or sleep interruptions.

Sleep inertia: the groggy, disoriented feeling that can accompany waking up

Sleep inertia is the groggy, disoriented feeling that can accompany waking up. People with sleep inertia may feel drowsy, have slower reaction times, impaired cognitive ability, and fuzzy thinking. Sleep inertia can negatively impact essential cognitive functions, such as decision-making, and can be particularly common in those with alternative sleep schedules.

There is no consensus on why sleep inertia occurs, but researchers have developed several theories. One theory suggests that sleep inertia results from being awoken during deep sleep and having the sleep cycle interrupted. During sleep, a sleeper passes through four stages, separated into non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep. NREM sleep has three stages, the third of which is called deep sleep or slow-wave sleep. Deep sleep is important for healing, immune function, long-term memory, and general refreshment. It is harder for a person to awaken from deep sleep, and the longer a person sleeps, the more likely they are to enter deep sleep and experience sleep inertia upon waking.

Another theory suggests that sleep inertia is caused by an increase in delta waves in the posterior part of the brain. Delta waves are most commonly seen in the NREM stage of sleep and 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 is suddenly awoken during NREM sleep.

A third theory proposes that sleep inertia is caused by high levels of adenosine, a nucleic acid compound found in the brain that plays a pivotal role in sleep and wakefulness. Upon waking, adenosine levels should be low, but research suggests that sleep inertia could be caused by high levels of adenosine upon waking.

Sleep inertia usually lasts for 15 to 60 minutes but can last for up to a few hours. It can be mitigated by consistent wake-up times, natural light exposure, and gentle alarms. Caffeine, bright light exposure, and washing the face can also help to reduce sleep inertia and restore alertness.

Acid reflux: a backup of stomach contents and acids into the oesophagus

Acid reflux is when there is a backup of stomach contents and acids into the oesophagus. This can cause a painful, burning sensation in the chest, known as heartburn, and a sour taste in the mouth. It can also cause nausea and a reduced appetite.

Acid reflux occurs when the lower oesophageal sphincter (LES) weakens or relaxes, allowing acid to pass from the stomach into the oesophagus. The LES is a circular muscle that opens to let food pass into the stomach and closes again to keep substances in the stomach. It also opens a little to let gas out when you burp or have hiccups.

There are several factors that can contribute to the weakening of the LES, including:

• Lying down too soon after eating
• Hiatal hernia
• Pregnancy
• Obesity
• Smoking
• Alcohol consumption
• Certain medications
• Fatty foods

Acid reflux is a common condition, and occasional episodes are usually manageable at home. However, chronic acid reflux, known as gastroesophageal reflux disease (GERD), can damage the oesophagus and affect your quality of life. GERD is estimated to affect about 20% of adults and 10% of children in the U.S.

If you experience frequent acid reflux, it is recommended to make lifestyle changes such as losing weight, quitting smoking, avoiding fatty foods and alcohol, and eating dinner earlier in the evening. Over-the-counter medications such as antacids and alginates can also help neutralise stomach acid and provide relief. If these measures do not help, prescription medications such as H2 blockers and proton pump inhibitors (PPIs) may be prescribed to reduce stomach acid production.

Hormone levels: lower levels of cortisol at night enable symptoms to flare

Cortisol, also known as the "stress hormone", is an important factor in regulating sleep. It is produced by the hypothalamic pituitary adrenal axis (HPA axis), which is part of the central nervous system and the endocrine system. Cortisol helps us feel alert and regulates our sleep-wake cycle.

Cortisol levels typically follow a 24-hour circadian rhythm, with levels highest in the morning to help us wake up, and lowest in the evening to help us fall asleep. However, if cortisol levels are too high in the evenings, it can cause insomnia and other sleep problems.

High cortisol levels in the evening can be caused by short-term stressors, prolonged light exposure, or shift work. This can lead to a vicious cycle, as sleep loss is also a stressor that increases cortisol levels. Additionally, lower levels of cortisol at night can cause other hormone levels to become imbalanced, making you feel worse.

To reduce high cortisol levels at night, it is important to lower stress levels, create a relaxing bedtime routine, improve your diet, and enhance sleep hygiene. This includes reducing screen time, spending time in nature, exercising during the day, and doing relaxation exercises such as deep breathing or meditation.

By managing cortisol levels and maintaining healthy sleep habits, you can keep your hormones in balance and improve your overall sleep quality.

Circadian rhythm: our internal clock that signals immune cells to be more active at night

Circadian rhythm is like an internal clock that helps control the changes that happen in your body throughout the day. It is influenced by factors such as sleep, light exposure, exercise, and stress levels. This internal clock also affects the immune system, with immune cells being more active at night.

The circadian rhythm controls the daily oscillations of the immune system, including the recruitment of immune cells to tissues and the expression of adhesion molecules and chemokines. The immune system's response to acute inflammatory insults and the onset of diseases also exhibit circadian rhythms.

During the resting phase, the number of circulating immune cells, such as hematopoietic stem and progenitor cells, peak in the circulation. In contrast, the migration of these cells to tissues occurs during the active phase. This circadian rhythm in leukocyte trafficking is regulated by sympathetic nerves and the expression of adhesion molecules and chemokines.

The circadian rhythm also influences the immune system's response to pathogens and inflammatory insults. Mice, for example, exhibit enhanced sensitivity to detect pathogens during their active phase due to increased expression of components of the innate immune system. The response to bacterial endotoxins and the survival rate upon exposure to them also vary depending on the time of day.

Furthermore, chronic diseases like rheumatoid arthritis and cardiovascular complications exhibit circadian exacerbations in symptoms, which has been linked to the circadian expression of pro-inflammatory mediators.

In summary, the circadian rhythm plays a crucial role in regulating immune functions, with immune cells being more active at night. This internal clock helps coordinate the daily oscillations of the immune system, influencing the recruitment of immune cells, the expression of adhesion molecules, and the response to inflammatory insults and diseases.

Body position: lying down allows mucus to pool at the back of the throat

Feeling unwell after sleeping during the day can be caused by a variety of factors, including body position. When you lie down, mucus can pool at the back of your throat, causing congestion and pressure in your sinuses, which may result in a headache or sinus pain. This is known as postnasal drip and can lead to a chronic cough, sore throat, and the urge to clear your throat frequently.

Postnasal drip occurs when excess mucus builds up and drips down the back of your throat. The glands in your nose and throat typically produce one to two quarts of mucus per day, which serves several important functions, such as moistening and cleaning your nasal lining, trapping and clearing particles you inhale, and helping to fight infections. Usually, you swallow mucus without noticing, as it mixes with your saliva. However, when excess mucus builds up, you may feel it dripping down your throat, causing irritation and discomfort.

In addition to body position, postnasal drip can be caused by various factors, including allergies, infections, pregnancy, medications, and gastroesophageal reflux disease (GERD). Allergies are one of the most frequent causes, as the body produces extra mucus to eliminate allergens like pollen. Cold temperatures, changing weather, and dry air can also irritate the nose and throat, triggering increased mucus production.

To manage postnasal drip, you can try propping your head up with pillows while sleeping, which promotes mucus drainage and reduces the amount of mucus in your throat. Drinking plenty of fluids can also help thin the mucus and keep it flowing smoothly. Over-the-counter medications, such as decongestants, antihistamines, and mucus-thinning medications, can be effective in drying out or thinning the mucus. Additionally, saline nasal sprays or irrigation pots can help flush out mucus buildup and clear blocked airways.

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