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Second wind (or third wind, fourth wind, etc.), a colloquial name for the scientific term wake maintenance zone, is a
sleep
Sleep is a sedentary state of mind and body. It is characterized by altered consciousness, relatively inhibited sensory activity, reduced muscle activity and reduced interactions with surroundings. It is distinguished from wakefulness by a de ...
phenomenon in which a person, after a prolonged period of staying awake, temporarily ceases to feel drowsy, often making it difficult to fall asleep when exhausted.
They are the result of
circadian rhythms
A circadian rhythm (), or circadian cycle, is a natural, internal process that regulates the sleep–wake cycle and repeats roughly every 24 hours. It can refer to any process that originates within an organism (i.e., endogenous) and responds to ...
cycling into a phase of wakefulness. For example, many people experience the effects of a second wind in the early morning even after an entire night without sleep because it is the time when they would normally wake up.
While most "winds" coincide with the 24-hour cycle, those experiencing extended sleep deprivation over multiple days have been known to experience a "fifth day turning point".
Characteristics
The "second wind" phenomenon may have
evolved
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation t ...
as a survival mechanism as part of the
fight-or-flight response
The fight-or-flight or the fight-flight-or-freeze response (also called hyperarousal or the acute stress response) is a physiological reaction that occurs in response to a perceived harmful event, attack, or threat to survival. It was first des ...
, allowing sleep-deprived individuals briefly to function at a higher level than they would without sleep deprivation.
Performance enhancement
One study presented a series of tasks of increasing difficulty to 16 young adults who had not slept in 35 hours and observed heightened activity in several brain regions using
magnetic resonance imaging
Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio wave ...
.
Researcher Sean P.A. Drummond commented that the ability to summon a second wind allowed them to "call on cognitive resources they have that they normally don't need to use to do a certain task". (He also noted that their performance, though an improvement considering their state of sleep deprivation, were below what it would be had they slept.)
Another study found significant improvement in the performance of 31 adults on various neurobehavioral tests after the onset of the wake maintenance zone as compared to their performance just three hours prior, despite the fact that the subjects had been awake longer.
The improvement as test subjects caught another wind was even more pronounced on the second day of extended wakefulness. A later study reproduced similar results.
Duration
The wake maintenance zone generally lasts 2 to 3 hours, during which one is less inclined to fall asleep.
[ While potentially useful for completing urgent tasks, it may have a potentially unwanted side-effect of keeping one awake for several hours after the task has been completed. The hypervigilance and stimulation brought on by a second wind can cause fatigue, which, in the case of infants, can be literally painful.][ Thus, an infant may begin crying when sleep habits are disrupted.
]
"Fifth day turning point"
Multiple studies have observed that individuals subjected to total sleep deprivation for extended periods spanning multiple days may feel "helplessly sleepy" up until the fifth day, upon which all observed individuals would feel what may be described as a second wind. This particular form of the experience has been dubbed the "fifth day turning point" (Pasnau et al. 1968).
Causes
There are multiple possible ways by which a person may experience a second wind, depending on the time of day. A second wind at around 6:008:00a.m. may be explained by cortisol
Cortisol is a steroid hormone, in the glucocorticoid class of hormones. When used as a medication, it is known as hydrocortisone.
It is produced in many animals, mainly by the ''zona fasciculata'' of the adrenal cortex in the adrenal gland ...
, a light-triggered hormone, peaking at that time. Cortisol helps facilitate adrenaline's role in glycogenolysis
Glycogenolysis is the breakdown of glycogen (n) to glucose-1-phosphate and glycogen (n-1). Glycogen branches are catabolized by the sequential removal of glucose monomers via phosphorolysis, by the enzyme glycogen phosphorylase.
Mechanism
The ...
and, therefore, in glucose release, which helps maintain wakefulness. As late afternoon transitions into evening, changes in light levels can stimulate the suprachiasmatic nucleus
The suprachiasmatic nucleus or nuclei (SCN) is a tiny region of the brain in the hypothalamus, situated directly above the optic chiasm. It is responsible for controlling circadian rhythms. The neuronal and hormonal activities it generates regula ...
in the brain to promote an arousal signal. At about 10:30p.m. (depending on factors including the season and the condition of the individual), melatonin
Melatonin is a natural product found in plants and animals. It is primarily known in animals as a hormone released by the pineal gland in the brain at night, and has long been associated with control of the sleep–wake cycle.
In vertebrates ...
the hormone responsible for preparing the body for sleeppeaks; a second wind may occur at this time if a person resists sleeping or fails to fall asleep before the peak.[ Such second winds could aggravate ]sleep debt
Sleep debt or sleep deficit is the cumulative effect of not getting enough sleep. A large sleep debt may lead to mental or physical fatigue, and can adversely affect one's mood, energy and ability to think clearly.
There are two kinds of sleep ...
.
In 2018, the second wind phenomenon, or "forbidden sleep zone of the wake maintenance zone", in scientific terms, was found to be caused by the buildup of dopamine in proportion to the time spent awake, as a paradoxical counterbalance to adenosine, the hormone of sleep pressure.
Although there is one zone of minimal sleep tendency, which is often termed the "wake maintenance zone" "approximately one to three hours before habitual bedtime", there are several other zones of lower sleep tendency; hence, these zones should be collectively termed "wake maintenance zones" in the plural, or the more colloquial "sleep gates".
Interactions with medications
When hypnotic medications are administered too early in the evening, such medications may reach peak their levels in the blood during the wake maintenance zone. Not only could this negate the soporific
Hypnotic (from Greek ''Hypnos'', sleep), or soporific drugs, commonly known as sleeping pills, are a class of (and umbrella term for) psychoactive drugs whose primary function is to induce sleep (or surgical anesthesiaWhen used in anesthesia ...
effectiveness of the medication, it may also cause users of the drug to experience disinhibition
In psychology, disinhibition is a lack of restraint manifested in disregard of social conventions, impulsivity, and poor risk assessment. Disinhibition affects motor, instinctual, emotional, cognitive, and perceptual aspects with signs and symptom ...
, hallucinations, or other dissociative phenomena, should they remain awake.[
]
See also
* Sleep state misperception
Sleep state misperception (SSM) is a term in the International Classification of Sleep Disorders (ICSD) most commonly used for people who mistakenly perceive their sleep as wakefulness,Minecan, Daniela, and Antonio Culebras. http://www.medlink.com ...
* Insomnia
Insomnia, also known as sleeplessness, is a sleep disorder in which people have trouble sleeping. They may have difficulty falling asleep, or staying asleep as long as desired. Insomnia is typically followed by daytime sleepiness, low energy, ...
* Hypnophobia
The English language, English suffixes -phobia, -phobic, -phobe (from Ancient Greek, Greek φόβος ''phobos'', "fear") occur in technical usage in psychiatry to construct words that describe irrational, abnormal, unwarranted, persistent, or ...
* Circadian rhythm
A circadian rhythm (), or circadian cycle, is a natural, internal process that regulates the sleep–wake cycle and repeats roughly every 24 hours. It can refer to any process that originates within an organism (i.e., Endogeny (biology), endogeno ...
* Delayed sleep phase syndrome
Delayed sleep phase disorder (DSPD), more often known as delayed sleep phase syndrome and also as delayed sleep–wake phase disorder, is a delaying of a person's circadian rhythm (biological clock) compared to those of societal norms. The diso ...
References
{{DEFAULTSORT:Second Wind (Sleep)
Sleep physiology