Counting Sheep: The Science and Pleasures of Sleep and Dreams. Paul Martin

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СКАЧАТЬ why we feel hot and sleepy when we have a bad infection. The fever response is a defence mechanism found in all animals: the rise in body temperature makes life harder for the offending bacteria or viruses, and the lethargy forces the infected organism to curl up in a dark corner and sleep until it has recovered. It all makes good biological sense.

      The brain and the immune system are interconnected through an elaborate network of chemical and neural communication channels. One important link between sleep, immune function and psychological stress is the steroid hormone cortisol. Sleep deprivation and prolonged stress both provoke an increase in the level of cortisol. After one night of sleep loss, your cortisol levels would typically be raised by about 45 per cent the next evening. It is not good to have elevated cortisol levels for too long, since cortisol has a powerful suppressive effect on the immune system. The functioning of the immune system is also intimately bound up with the 24-hour sleep – wake cycle and the circadian rhythms in hormone levels. Various aspects of immune function fluctuate in tune with the circadian cycle. Anything that disrupts the normal cycle of sleep and wakefulness therefore tends to disturb the immune system, with potential consequences for the body’s ability to defend itself against infection and disease.

      The intimate relationship between sleep and immune function takes on a potentially huge practical significance when you consider how widespread sleep deprivation has become in society. Tired people are more likely to become sick people.

The Battle of Stalingrad

      O, I have passed a miserable night,

      So full of fearful dreams, of ugly sights

      William Shakespeare, Richard III (1591)

      Prolonged sleep deprivation, uncontrollable stress and starvation make a lethal cocktail, as Hitler’s troops found to their cost during the Battle of Stalingrad in World War Two. In June 1941 German forces invaded the Soviet Union and were soon threatening Moscow. The capture of Stalingrad on the River Volga became a key strategic objective. Stalin decreed that the city must be defended to the bitter end. The titanic struggle that ensued cost the lives of at least 800,000 Axis soldiers and 1.1 million Soviet soldiers.

      The fight for Stalingrad (now renamed Volgograd) began in earnest in the summer of 1942, as the Germans advanced rapidly towards its suburbs. There was fierce Soviet resistance and the fighting dragged on into the harsh Russian winter. By September 1942 the battle was being waged at close quarters among the buildings, cellars, sewers and bunkers of ‘the Stalingrad Academy of street-fighting’.

      To increase the pressure on their opponents, the Soviet commanders ordered continual raids to be carried out by night. They did this partly because the Germans lacked protection from their air force at night, but mainly to induce exhaustion among the enemy. To augment the night raids, the Soviets fired flares indicating that an attack was imminent even when it was not. Their air force also attacked German positions every night. The Soviets kept up the psychological pressure throughout the night, with loudspeakers blaring out propaganda broadcasts, surreal tango music, or the sound of a ticking clock. The strategy was highly effective. ‘We lie exhausted in our holes waiting for them,’ wrote one German soldier. The German commanders begged for air support, citing their men’s exhaustion.

      The German troops’ health started to deteriorate badly even before the dreadful Russian winter had begun to bite. There was a sharp rise in deaths from infectious diseases including dysentery, typhus and paratyphus. The actual prevalence of these diseases was not much worse than it had been a year earlier, but the numbers of infected men who were dying from them increased fivefold. It was as though the German soldiers had lost their capacity to resist infection. The Russians noticed this phenomenon, which they referred to as ‘the German sickness’.

      In November 1942 the Russians launched a huge and ultimately successful counteroffensive that soon had the Germans encircled within the ruined city. But the Germans were under orders from Hitler not to surrender, and so they fought on through December while the Russians gradually tightened the noose. Conditions for the German troops became appalling as their supply lines were cut off and the Russian winter froze them. There was hardly any food and little or no medical care.

      In mid-December 1942 the German military doctors in Stalingrad noticed a new phenomenon: more and more apparently healthy troops were suddenly dying for no obvious reason. The Germans were unsure whether the deaths were the result of starvation, exposure, exhaustion or an unidentified disease. A German army pathologist named Girgensohn, who was sent to Stalingrad to investigate the problem, became convinced that a combination of exhaustion, stress, cold and lack of food was responsible for the much higher death rate. The Russian night attacks and round-the-clock activity had caused severe sleep deprivation, and Girgensohn concluded that this had amplified the effects of the food shortage by ‘upsetting the metabolism’ of the exhausted Germans. We know now that one symptom of prolonged sleep deprivation is a marked increase in metabolic rate and hence the requirement for food. Whatever the precise explanation, the pressure was too much for the Germans. In February 1943 the Battle of Stalingrad finally ground to a halt, as the crushed and starving remnants of the German army surrendered.

Sleepless in hospital

      I have the feeling that once I am at home again I shall need to sleep three weeks on end to get rested from the rest I have had.

      Thomas Mann, The Magic Mountain (1924)

      Sleep is good for you and lack of sleep is bad. It therefore seems odd that hospitals, which are supposed to promote recovery, are usually dreadful environments for sleeping. ‘The hospital bed,’ wrote one historian, ‘is one in which normal sleep is forbidden.’ A Punch cartoon of 1906 shows a patient being told to ‘wake up and take your sleeping-draught’. Things have improved since 1906, but not much.

      Sick people really do benefit from sleep. We saw earlier how the brain and the immune system respond naturally to infection by inducing sleep. This helps the body cope with disease in several ways. The production of growth hormone occurs mainly during sleep, and growth hormone aids physical recovery by promoting the healing of mucous membranes and in other ways. The hormone melatonin, which is also produced at night, boosts immune responses, inhibits the growth of tumours and enhances resistance to viral infections. Conversely, sleep deprivation impairs immunity and slows the healing process. Given the importance of sleep for recovery, it is ironic that hospital patients are routinely subjected to conditions that make normal sleep almost impossible.

      Sick people start with big disadvantages, of course. Pain is a powerful disrupter of sleep. Patients suffering from chronic, severe pain often become exhausted. Disrupted sleep is a common complication of burn injuries, for example. Studies have found that between half and three quarters of burns patients experience significant sleep disturbances. Sleep problems are common among cancer patients too. Fatigue can become one of the most distressing aspects of having cancer, severely reducing the quality of life. While medical treatments for cancer have advanced apace, efforts to improve patients’ quality of life by alleviating their fatigue have lagged behind.

      To make matters worse, tired people are more sensitive to pain. Sleep deprivation lowers pain thresholds, generating a vicious cycle in which pain disrupts sleep, the resulting sleep loss makes the pain feel even worse, and so on. An investigation of patients with burns injuries uncovered a systematic link between the quality of their sleep and subsequent pain. Patients who slept poorly during the night experienced more intense pain the following day, because the fatigue intensified their perception of pain.

      One of the worst places imaginable СКАЧАТЬ