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There’s nothing better than falling into bed at the end of a long day, or waking up in the morning feeling rested and refreshed. We all spend roughly a third of our lives asleep, but how much do we really think about it? With more and more of us working, studying, and partying until late at night, how many of us actually get enough sleep? It is essential for our health and wellbeing, and this article aims to highlight some of the reasons why.
In a study of college students, 68.9% of pupils reported having insufficient sleep on school nights. This lack of sleep was not only linked to a general feeling of sleepiness in class, but also to a long list of unhealthy behaviours including smoking, drug and alcohol use, and lack of physical activity. Interestingly, lack of sleep has repeatedly been linked to an increased risk of obesity and weight problems. Having a shorter time asleep could result in the loss of one of the rapid eye movement (REM) periods of sleep, in which the eyes move rapidly and the brain is most active. A loss of this REM period may increase appetite, and lead to a higher intake of high fat and carbohydrate snacks.
Type 2 diabetes, a disease clearly linked to obesity, also shows an association with lack of or disturbed sleep. This could be due to the hormone disturbances that come with restricted sleep, leading to a higher likelihood of insulin resistance. Thus, it is evident that prolonged sleep deprivation affects your long-term health; beyond the effects we might immediately see or feel.
Athletic performance is also impacted by sleep deprivation, particularly when the task is of longer duration, which is likely due to increased fatigue and a loss of motivation. It appears however that shorter duration; high-power performances were not affected to the same extent by sleep deprivation. Taking an afternoon nap after a sleepless night was shown to improve performance, reducing tiredness and enhancing readiness to participate. This provides a possible explanation to why athletes must ensure that they are rested, particularly those participating in endurance sports. This is also likely to be why athletes make sure they have a few days to adjust when they compete in a different country, to avoid jet lag (which we’ll come on to...).
I’m sure we’re all aware, when children are tired, they become more emotional and perhaps unsurprisingly, this link has also been made in adults. We’ve all been there, becoming more emotionally reactive, with mood swings and altered processing of our emotions when we are sleep deprived. Of course, powerful emotions can also affect our ability to sleep, as our sleep affects our emotional state and this is a two-way street, with sleep and emotions being deeply intertwined.
Our decision making, cognitive, sensing and processing abilities and memory are also negatively impacted by reduced sleep. In one study, sleep-deprived participants made more economically risky decisions, and had an increased likelihood of exhibiting unethical behaviour than those who had slept well. Young adults also showed slower reaction times and poorer performance in cognitive tests following sleep deprivation. It has also been shown that sleep is essential for the formation of memories; we remember things better after a good nights sleep, as opposed to spending the same amount of time awake. So maybe a good night’s sleep before exams really is better than cramming until 3am…? I’ll leave that with you.
There is also a significant link between sleep and mental health disorders.Patients with major depressive disorder, bipolar disorder and ADHD (attention-deficit hyperactivity disorder) have been shown to have higher rates of sleep deprivation and disturbance, or lack of a stable sleeping pattern. Interestingly, a loss of normal rhythmicity in sleeping patterns has been seen in patients 10 months before a clinical diagnosis of Alzheimer’s disease can be made, which could be an interesting early biomarker (a characteristic which allows you to identify a disease), possibly allowing treatment to begin sooner.
Each of us has what is commonly referred to as a ‘body clock’; towards bedtime we begin to feel tired and sleepy, and towards the morning we become more awake. This can also be referred to as the sleep-wake cycle, which is one of the circadian rhythms in our body, occuring cyclically over 24 hours. A circadian rhythm is like an inner sense of time, which organises different biological systems and behaviours to interact with the outside environment as it changes.Left to ourselves, without exposure to markers of day and night (also called free-running), our natural rhythm runs for slightly longer than 24 hours, but the outside cues of daylight and night-time pull us towards a 24 hour daily rhythm. This rhythm can be affected by other external factors, such as a change in our sleeping patterns, shift work, and changing time zones. The jet lag feeling you experience when you travel abroad is simply due to this misalignment between the rhythm your body is following, and the contrasting external cues you see around you.
With circadian rhythms comes the idea of chronotypes, the thought that each of us has a slightly different rhythm, leaning towards a preference for either morning or evening, referred to as morningness and eveningness . There are also those with a preference for neither – those who are intermediate. There are a series of questionnaires to accurately determine your morning-evening preference, but it mostly boils down to your natural waking and sleeping times (earlier in those with a morning preference, later in the evening preference), and the time of day at which you perform best, either morning or evening.
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So what determines your chronotype? Associations have been made with age, sex, personality, and the strictness of bedtimes during childhood.As age increases towards adolescence, there is an increased eveningness, and individuals typically become more morning-oriented in adulthood. Interestingly, it is suggested that women have a higher likelihood of morningness, and men of eveningness. In studies done in both adults and adolescents, there were several different characteristics commonly associated with each chronotype. Morning types were more likely to be proactive, agreeable, conscientious and persistent, with lower levels of novelty seeking, smoking and alcohol use, and physical inactivity. Conversely, those with an evening preference showed greater sleep problems, poorer school performance, a greater tendency towards smoking, caffeine and alcohol consumption, and a higher level of physical inactivity. Whilst these are generalisations and correlations rather than causation, it remains to be investigated whether eveningness could be a marker or a predictor for mental disorders.
We can assume that the majority of us, spending a lot of our time in our modern homes, schools, and offices, spend most of our day under some sort of electric, or artificial light. Tablets, streetlights, computer screens, and televisions, the list is endless and it seems there really is no escape from artificial light in the modern world. There’s no doubt, of course, that this is useful for us in many ways, but it also seems it could have a negative impact on our health.
As mentioned above, our circadian rhythms rely on external light-related cues to determine our sleep-wake cycle and other bodily rhythms, such as hormone cycles. This is a problem particularly seen in night shift workers, who spend the dark hours inside under artificial lights. Increased levels of various cancers have been shown in people in these occupations, and whilst light levels do not categorically cause this, some studies have drawn links between these two factors. Even non-shift workers spend their days under the electric lights, and at night, very few people are able to sleep in a room that is totally dark. We check our phones, we read on our tablets, the lights on the street shine through the blinds, and our bedrooms are inevitably dimly lit. In actual fact, this can disrupt our circadian rhythms, our sleep-wake cycle, core body temperature, and the regulation of hormone release and gene expression throughout our body, affecting any number of different body systems. Maybe we should think twice before checking social media before going to sleep?
Photo credit: Pixaby