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Lecture notes for 2nd year medical students, Kulliyah of Medicine, International Islamic University, Kuantan Malaysia Saturday 13th March 1999 by Prof Dr Omar Hasan Kasule, Sr.
1.0 BIOLOGICAL CLOCK/DIURNAL RHYTHM
Day and night: The change or alternation of day and night is among the signs of Allah for those with insight (24:44).
Bio-rhythm: Several biological phenomena are affected by the diurnal variation. Examples of bio-rhythm are: sleep, cortisol, and melatonin secretion. Release of melatonin from the pineal is controlled by light and dark cycles. It is released in the dark and not in light hours. Light entering the eyes stimulates the CNS which in turn stimulates the pineal gland to inhibit melatonin release.
2.0 NATURE OF SLEEP
Qur'anic terminology for sleep: Four terms are used by the Qur'an to refer to various forms of sleep: nuas, sinat, and naum. The Qur'anic term nuas refers to drowsiness or dozing, a type of sleep (3:154, 8:11). Nuas is good as a preliminary to deep sleep. It is bad during salat. Salat is delayed in cases of nuas so that mistakes are not made (KS p. 315, MB #161 p 127, #162 p 127, Muslim 1718, 1719). Nuas is condemned during salat al jumu'at because of the necessity of paying full attention to the sermon (KS p. 158). The Qur'an described sinat as a minor form of sleep (2:255). Naum is the general term for sleep. The Qur'an uses the term yaqdhat to refer to waking up from sleep or to being awake and alert (18:18).
Physiology of sleep: Sleep is a recurrent reversible phenomenon. Some bodily functions are diminished whereas others are increased but no functions ever stop completely. The following are diminished in sleep: muscle inertia, basal metabolic rate, and sensory reactivity to the environment. On the other hand mitosis and electrical activity in the brain are increased. The increased brain activity is due to rearrangement of the data-base to include new information garnered during the day.
Equilibrium: Sleep and wakefulness are a balance between the activation of the raphe nuclei, the sleep system, and the ascending reticular formation, the wake system. Thus sleep and wakefulness are on a wide spectrum depending on the relative activity of the two opposing systems of wakefulness and sleep. The reticular activation system, RAS, is a collateral sensory pathway that is responsible for maintaining the conscious alert state.
Sleep and death: The Qur'an and sunnat described sleep as a type of death (6:60, 39:42. MB #2073 p 973). Some who go into sleep may never wake up again. The Prophet taught special supplications, dua, on falling asleep and on waking up in view of sleep being a major transitional event.
Sleep is Allah’s sign: The ability of humans to sleep and wake up is one of the signs of Allah (30:23). It is also a blessing for humans because their life would have been very exhausting if there were no periods of rest and sleep.
Sleep is a human attribute: Humans and other living things created by Allah can fall asleep. Sleep is a form of inactivity and inattentiveness to the environment that are not compatible with divine attributes. Allah who has to look after the whole universe and its contents does not fall asleep (2:255)
Sleep is an active function: We know from studies of physiology and the evidence from the sunnat that sleep is not a passive activity. There are many intellectual and physiological processes that continue during sleep. Some of these are even enhanced during sleep. The Prophet was described as sleeping with the eyes but not with the heart (MB #2213 p 1028). Sleep is not an intellectually passive activity. Thinking and memory take place. Humans are not conscious of much of this activity. Mitotic activity is highest during sleep. It is least during vigorous exercise and stress because hormones associated with stress inhibit mitosis. Metabolism continues during sleep but at a lower rate. The Prophet forbade missing supper, tark al asha, (al tirmidhi & Ibn Majah). This is understood to mean that the body needs food energy during the night because metabolism does not stop during sleep.
Sleep and legal responsibility: Sleep involves a temporary suspension of full sensory perception and interaction with the environment. A sleeping person is not legally accountable for the period during sleep (KS p. 192). If a person misses undertaking an obligatory act because of sleep, he or she is excused under the law. In the same way deep sleep abrogates wudhu because there is no way of telling what actions the sleeping person could have undertaken during sleep resulting in abrogation of wudhu. It is for example possible that a sleeping person touched the genitals and thus abrogated wudhu without being aware of it.
Times of salat and sleep: Sleep may prevent a person from performing salat at the right time. Shaitan tries his best to prevent a sleeping person from waking up at the time of salat (KS 49).
3.0 PURPOSE OF SLEEP
Sleep is a biological imperative: an adult needs 8-9 hours of sleep in a 24-hour cycle. Sleep can not cheated. Long-term deprivation of sleep leads to psychological and physiological problems.
Sleep and rest: The human organism needs rest, raahat al jism (p 461 7:163, 7:189, 10:67, 16:6, 21:20, 25:47, 27:86, 28:72-73, 30:21, 40:61, 43:74-75, 78:9). The period of sleep is an opportunity for the human to rest the body and the mind (78:9). This rest is both psychological (decreased anxiety and sensory stimulation) and biological (lower respiration and circulation). During sleep there is decrease in urinary excretion, lachrymal, nasal, oral, and throat secretions. The heart and respiratory rates are decreased. Body temperature is lowered. Pupils are constricted. Cold-blooded animals such as reptiles and amphibians can hibernate for long periods of time during which they have a very low metabolic rate. Sleep could be looked at as a type of hibernation but less profound than that of the frog.
Sleep as ibadat: Sleep is an act of ibadat that is opened and is closed by special supplications, dua. There is a dua before sleeping (Ibn al Qayim p. 248-9). Another dua is recited on waking up. A special dua is recited on waking up during the night. Waking up at night for salat gives energy (Ibn al Qayim p. 253) for the next day's work.
4.0 NORMAL SLEEP
EEG patterns of sleep: Electrophysiological studies have enabled us to understand many phenomena related to sleep. Using the electro-encephalogram (EEG), 3 patterns of sleep have been identified according to the pattern of electrical waves recorded: alpha, beta, theta, and delta sleep patterns.
Types, stages, and cycles of sleep: There are 2 types of sleep, REM and non-REM. In REM sleep there is rapid eye movement and intense electrical activity in the brain. Non-REM sleep is electrically more quiescent. There is cyclic alternation between REM and non-REM sleep. Different events and mental experiences occur in REM and non-REM sleep. There are 5 stages of sleeping. There is a gradation in depth of sleep from stage 1 to stage 5, stage 1 being the lightest and stage 5 the deepest sleep. Stages 1-4 are in REM sleep is REM. Stage 5 is non-REM.
Etiquette of sleeping: The Prophet taught sleeping on the right side of the body (MB# 2074 p 973, Ibn al Qayim p. 247. He forbade sleeping on the face (Ibn al Qayim p. 248-9). Further medical research will uncover the physiological basis for these prophetic recommendations.