Introduction Stress is the body’s response towards daily life, in terms of noxious stimuli. There is a correlation between the severity of the stress response, due stimulus intensity, with the length of sleep. The process of sleep is a function of the body by which several hours are used to act on the regulatory systems of the internal environment; balancing out hormone production and breakdown and maintaining a healthy immune system. The average human can survive several days of sleeplessness but the reduction of sleep periods can result in diminishing heath and functioning. (David T. Derrer, 2014)

This essay attempts to look at the various causes and subsequent outcomes of sleep deprivation.

Types and Causes Sleep deprivation occurs when sleep is insufficient to support typical body functions, either as a result of an inefficient sleep period (quantity) or a disturbance in sleeping pattern (quality). It can be either acute; no sleep/ a reduction in total sleep time or it can be chronic; where an individual consistent sleep levels are less than that required for optimal functioning. (ORZEŁ-GRYGLEWSKA, 2010)

General sleep reduction- caused by daily sleep time reduction below level of optimum needs, absence of a single nights sleep or a shift in sleep in relation to circadian pattern. Examples include social eccentrics (partying), late shifts of work and general factors from contemporary lifestyle. Considerable sleep reduction- caused by lengthened insomnia over several days or complete sleep deprivation. Examples would include, experimental conditions or possible extreme situations, i.e., torture. Sleep reduction due to pathological processes- caused by depression, anxiety disorders, addiction/ chemical substance abuse, somatic/painful diseases or sleep disorders, i.e., subjective, idiopathic and psychophysiological insomnia. The sleep in these disorders is of low quality, delayed and shortened, and some genetic factors or enhanced by old age and chronic stress or traumatic experiences. (ORZEŁ-GRYGLEWSKA, 2010)

These different types of sleep deprivation can roll on to have an effect on the different systems inside the body as well as cognitive and general body function. Discussed below in more detail.

Effects

Physiological Cardiovascular Effects

• Sleep deprivation, like smoking is now noted as one of the main causes of developing heart disease. The possible reasoning for this, is that a decrease in sleep results in increased blood pressure, and sympathetic overactivity; known precursors for developing coronary heart disease. Sleep deprivation may be caused by sleep apnea which also can be a factor in developing heart disease (Quan 2009).

Increased Blood Pressure and Sympathetic Overactivity

Studies performed on healthy individuals, showed a significantly larger systolic blood pressure following one night of sleep deprivation, compared with non-sleep deprived individuals. One experiment examined the theory of this systolic increase being linked with stress induced reaction. They created a control, where subjects where not exposed to any form of stressful situation following sleep deprivation (Franzen et al., 2011). The same increase in systolic pressure was observed. Therefore highlighting a clear link between sleep deprivation and increased blood pressure. Without adequate rest periods sympathetic overactivity results. Normally, heart rate is controlled by a balance between the parasympathetic nervous system and the sympathetic nervous system. The parasympathetic innervation via the vagus nerve causes a decrease in heart rate by having a direct depressor effect on the sympathetic nervous system. Sympathetic nervous system elevates the heart rate by causing an muscarinic Acetylcholine activated elevation in cAMP, which causes elevation in heart rate Sympathetic overactivity, leads to inadequate depression via the parasympathetic vagus nerve and the heart rate remains increased as a result. Figure 1.1 highlights the parasympathetic suppressant effect on the heart rate. Long term sympathetic over-excitability results in hypertension, which leads to cardiovascular disease (Ayas et al., 2003).

Fig 1. Sympathetic and Parasympathetic control of Heart Rate. This shoes the effect of the parasympathetic and sympathetic system on heart rate. Elevation in sympathetic activity counteracts the depressor effect of the parasympathetic system thus, resulting in increased heart rate.