Third year, Sarah Levy, looks at the medical effects of sleep deprivation and its prevalence in the UK.
Being the fact-cramming, society-juggling, library-living, pub-frequenting multitaskers that they are, it is hardly surprising that medical students often have to sacrifice something in order to maintain at least half-decent grades and some semblance of a social life. For many, a decent night’s sleep is the first luxury to be lost. Although sleep deprivation is particularly common among medical students, for whom a work-life balance can be hard to achieve, it is most certainly not restricted to those in the medical profession. Indeed, a recent study carried out by the UK Sleep Council aptly entitled the “Great British Bedtime Report” found that 33% of the population sleep five to six hours a night, with 70% sleeping for seven hours or less. In addition, of those participating in the study, 27% described their sleep as being of “poor quality” on a regular basis.
But How Much Do I Need?
Although scientists have generally concluded that there is no official optimal amount of sleep, with values depending on age, genetic factors, activity levels etc., it is generally concluded that most adults function at their best on 7-8 hours of sleep a night. A study investigating the link between sleep amount and sickness absence in 3760 individuals concluded that the optimum was 7.8 hours for adult men and 7.6 hours for adult women. Worryingly, less than a quarter of adults questioned by the UK Sleep Council regularly sleep this amount. A variety of factors have likely resulted in this, including heavy work pressure, depression, insomnia and other conditions that make sleep difficult. 47% of those questioned said that they found themselves lying awake at night preoccupied by stress and worry.
And Why Can’t I Get Out of Bed in the Mornings?
A common sleep-related problem among both teenagers and university students is that of being excessively tired in the morning and then becoming more alert late in the evening. There is no doubt that a combination of factors is to blame for this. For instance, increased academic pressures lead to students delaying their bedtimes in order to study.
Similarly, as a person progresses from childhood into adulthood the timings of social events become later, meals times tend to be later and television programmes of interest are aired later. In addition, research has found that teens do not start producing melatonin until 1am on average, whereas their adult counterparts tend to commence production at 10pm. Melatonin is a hormone secreted by the pineal gland of the brain in response to darkness, which inhibits melanin formation and is thought to be involved in the initiation of sleep and maintenance of circadian rhythms. It has been hypothesised that this teenage delay in production could be due to a combination of the behavioural factors (e.g. late night computer use) and the complex interactions of the hormones involved in puberty.
The physiological effects of mild/partial sleep deprivation have been less studied than those of total sleep deprivation, but nevertheless there is clear evidence of the detriment it evokes on the body. Partial sleep deprivation has three main aetiologies. The first is sleep fragmentation, which has a variety of causes including obstructive sleep apnoea, and is classified by frequent waking after initiation of sleep. The second (much rarer) cause is termed selective sleep stage deprivation and involves the loss of specific physiological sleep stages. Finally, the most common cause of partial sleep deprivation is sleep restriction, which is typified by a reduction in sleep duration . This type of sleep deprivation has marked effects on cognitive performance, particularly behavioural alertness .
Psychomotor vigilance abilities are also adversely impacted. Psychomotor vigilance tasks are often used in studies on sleep, and generally involve measuring the reaction time of the subject to a visual stimulus over a 5 to 10 minute period. A study carried out by the renowned sleep expert Professor David Dinges found that the delays in the reaction to the stimuli following sleep deprivation can range from 0.5 seconds to over 10 seconds, and in wake of severe sleep deprivation, the subjects were even observed to have “full blown sleep attacks”, during which they were totally unreactive without additional stimulation . This is worrying, considering the percentage of the population who work in fields in which their own lives or the lives of others are potentially dependent on their ability to concentrate and respond to stimuli, for instance pilots, soldiers, firefighters and of course doctors. In addition, it is highly concerning that much of our population is sleep deprived enough to have impaired results in psychomotor vigilance tests, yet almost all of us would drive a car when tired. UK Government statistics state that approximately 20% of accidents on major roads are related to sleepiness and that sleep-related accidents are more likely to cause a fatality or serious injury .
Sleep also has known effects on mood. An American study has recently found that subjects who were limited to 4.5 hours of sleep per night for 7 days reported feeling more sad, angry, stressed and mentally exhausted. Interestingly on resumption of their normal sleep habits, they reported a dramatic improvement in mood .
In addition to cognitive, behavioural and emotional effects, sleep restriction also has chemical effects on the body. Studies have shown that sleeping 4-6 hours per night compared to 12 hours per night in young adults leads to an increased activation of the sympathetic nervous system, decreased glucose tolerance, decreased thyrotropin activity and elevated evening production of cortisol (a steroid hormone with actions including stimulation of gluconeogenesis). Increased risk of heart attack and stroke  and immune effects relating to elevation of specific inflammatory cytokines[ 12] have also been linked to chronic sleep deprivation. Sleep could even be contributing to the obesity epidemic affecting the Western World, with an American study concluding that of the 10,000 adults studied, those who slept less than seven hours a night were significantly more likely to be obese . Conversely, there are also detrimental effects associated with sleeping too much, which is generally defined as consistently more than 9/10 hours a night in adults.
Well, what can I do about it?
As mentioned above, optimal sleep amount for healthy adults is generally around 7-8 hours with significant variations from person to person. Signs that you are getting enough sleep include waking naturally in the morning without the aid of an alarm clock and not experiencing feelings of daytime drowsiness. If, on the other hand, you fall into the vast majority of students who struggle to roll out of bed to a 9am lecture or are even one of the nappers who can occasionally be spotted using a copy of Gray’s Anatomy as a pillow, do not despair. If the actual act of falling asleep proves difficult, the NHS Choices website advises having a regular bedtime routine, sleeping in a cool room and having a comfortable bed . However, if leading a busy life is the culprit then there is no quick fix. Work-related sleep deprivation is becoming endemic in the UK and is no doubt affecting the health and wellbeing of our nation. So if you want to feel happier, smarter, quicker and healthier, stop reading and go to sleep!
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- Dinges DF, Rogers NL, Baynard MD, editors. WB. Saunders; 2005. Chronic sleep deprivation
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