Sleep deprivation circadian rhythms

Existing mathematical models predicting cognitive readiness/performance from sleep/wake history are based on the interaction of three factors. These factors are sleep homeostasis, circadian rhythm, and sleep inertia (12). Three-factor models successfully predict performance effects of acute, total sleep deprivation and... 

One of the most consistent findings is the sleep disturbance that often precedes and may even trigger a manic phase ( 46). Studies on circadian rhythms have demonstrated that many aspects of the sleep cycle are phase-advanced in mania (i.e., occur earlier than normal), and often these patterns resemble the free-running rhythms seen in normal individuals who are removed from all time cues. In addition, there is a blunting of amplitude and a doubling of the sleep-wake cycle up to 48 hours. Lithium is known to delay the sleep-wake cycle and often slow such free-running rhythms, which in turn are partly modulated by neurotransmitters such as NE, 5-HT, and acetylcholine. Further, manipulation of the sleep-wake cycle may prevent a manic episode or be used to treat the depressive phase (e.g., sleep deprivation therapy see also the section Experiments in Chapter 8). 

Sleepiness is a primary symptom of narcolepsy, often preceding the onset of the other well-known symptoms of the disease, namely cataplexy, sleep paralysis, and hypnagogic hallucinations (44). Evaluation of the MSLT of narcoleptic patients has demonstrated a short sleep latency (<5 min) and multiple sleep-onset REM periods (SOREMPs). The more specific finding in the MSLT of narcoleptic patients is more than 2 SOREMPs, shown to reach a specificity of 99% by Amira et al. (45), which further increased to 99.2% if 3 SOREMPs were recorded (46). On the other hand, more than one SOREMP can occur in nonnarcoleptic patients, such as those with sleep apnea, sleep deprivation, depression, periodic limb movements, circadian rhythm disruption, or withdrawal from REM-suppressing medications (5,47). Thus, the findings of the MSLT, which is always performed for suspected narcoleptic patients, must be interpreted in view of the clinical history and nocturnal PSG. 

One reason why sleep tends to be inadequate during continuous operations is that even when they are sleep-deprived, commanders and soldiers are not always able to take full advantage of emergent opportunities to sleep. Their only opportunity for sleep may occur during the ascending phase of the circadian alertness rhythm, or the sleep environment may not be conducive because of noise, light, commotion, etc. It is under these operational circumstances that pharmacological enhancement of sleep may be useful. 

The increased mental drive necessary to maintain performance was apparent in another study of military recruits kept awake for 3 successive nights (18). An increase in fatigue was accompanied by a decline in rifle-shooting accuracy, both reflecting circadian rhythmicity over which the deteriorating trend was superimposed. There was a clear rhythm in circulating noradrenaline whose peak increased on each of the 3 days of sleep deprivation. 

Benoit O, Foret J, Merle B, Reinberg A. Circadian rhythms (temperature, heart rate, vigilance, mood) of short and long sleepers effects of sleep deprivation. Chronobiologia 1981 8 341-350. 

Patients wdth major depressive disorder are reported to have decreased latency to first episode of rapid eye movement (REM) sleep (Kupfer and Foster, 1972). This finding may relate to the hypothesized dysregulation in circadian rhythms found in mood disorders. This interest in circadian rhythms has lead to development of some specific treatments for depression, including sleep deprivation and light therapy. 

Melatonin has been used to regulate the sleep-wake cycle and is used often to treat insomnia. It is not recommended during pregnancy and breast-feeding becanse of a lack of information abont its safety. Lower doses of melatonin (e.g., 0.1-1 mg at bedtime) are effective in initiating sleep higher doses may not improve the hypnotic effect. The rednction in daytime snnUght, which increases melatonin secretion, may exacerbate PMS in the winter this type of seasonal mood disorder may respond to phototherapy. Early sleep deprivation also may help to correct circadian rhythm disturbances in PMDD. ... 

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