Sleep is important for a healthy life.
- central to human health and happiness
- plays a role in cerebral development
- crucial for maintenance of cognitive skills – thinking, speaking, learning.
Insomnia is a common problem that affects about a third of the population (NHS data). It is defined as difficulty with getting to sleep and staying asleep despite good opportunity for sleep resulting in daytime impairment.
Insomnia can come and go without affecting us, but when it becomes recurrent it can cause all sorts of secondary problems like mood swings, inability to concentrate and difficulty coping with life. It is then that we need to seek help. Our daily patterns of waking and sleeping are controlled biological rhythms, such as weather systems, phases of light and dark and temperature fluctuations. These affect our internal ‘clock’ that regulates our waking and sleeping cycle.
There are two prominent rhythms controlling our sleep cycle: the circadian rhythm that works over a 24-hour period, and the ultra-diem rhythm that operates on 90–120 minute cycles. Consequently, at predictable times during the day we become alert, sleepy, active, hungry, listless or energised and our body adjusts accordingly with changes in heart rate, blood pressure, hormone level and brain wave activity etc.
The base value of our biological rhythms is genetically pre-determined. The circadian mechanism is primarily initiated and governed by exposure to light first thing in the morning and to darkness at night. Additionally, the circadian mechanism takes its secondary cues from environmental signals such as meal times, social circumstances, and exercise patterns.
In the absence of natural light and other signals the elaborately intuitive rhythms of the body are thrown out of balance, promoting sleep disorders, hormonal imbalances, mood disturbances and generally compromised health and well-being. Examples of things that can affect are circadian rhythms are jet lag, travelling to the Northern latitudes, shift work, long spells in a dark room.
The neurotransmitters serotonin and melatonin control our daily body rhythms. Serotonin is made from the essential amino acid tryptophan (one of the building blocks of protein). Tryptophan is considered essential because the body cannot synthesise it and needs to be taken from the protein in the food we eat – like eggs, meat, cheese, tofu, green tea, dark chocolate, turmeric, cold-water fatty fish, nuts, and seeds.
Serotonin is found predominately in the gut, where 90 per cent of it is produced. A small amount of serotonin is produced in the large constricted blood vessels and in the Central Nervous System (CNS). Serotonin in the brain regulates mood, appetite and creates a general ‘feel-good’ vibe and helps us get on with daily life. Some people with clinical low serotonin levels resort to going to their doctor and they might prescribe anti-depressant drugs – selective serotonin re-uptake inhibitors (SSRIs) widely used antidepressant to treat anxiety and depression.
On the onset of darkness – some of our serotonin is converted into melatonin, which prepares the body for sleep. Melatonin levels in the blood starts to rise about two hours before your habitual bedtime, leaving you primed for sleep and they peak roughly two hours after you doze off. Levels decline during the night and are barely detectable during the day. Melatonin stays in our bodies for about 12 hours until the morning daylight turns off its production. We are left with just the serotonin again, which helps us through the next day. The daylight we receive through our eyes lets us know whether it is light or dark and the body produces serotonin all the time and melatonin only when light levels fall.
Life style factors inhibit melatonin production. For example, caffeine, alcohol, high Glycaemic Index (GI) foods (such as sugary sweets), UV light from electronic screens and anxiety and stress caused by psychological problems or pain. Unlike serotonin, production of melatonin decreases with age and consequently insomnia is more common in elderly people.
Brief overview of the stages of sleep
Sleep occurs in a recurring cycle of 90–120 minutes matching the body’s ultradian rhythm. It is divided into non-rem (rapid eye movement), slow-wave sleep, and REM sleep.
- Stage one – very light sleep – beta to theta waves (hypnogogic state)
- Stage two – true/light Sleep – theta waves – lasting 20 minutes per cycle.
- Stage three and four – slow-wave/deep sleep (delta waves) lasts around 30 minutes.