During the night we move in and out of sleep stages in approximately 60-90 minute cycles, interspersed with waking. (as below, table cited from CRUFAD). The first sleep cycles each night feature more deep sleep, in response to homeostatic drive build-up during the day, and less REM sleep. As the night progresses, time spent in deep sleep decreases as REM sleep periods increase. By morning, people will more likely wake from light sleep or REM sleep.

REM or rapid-eye-movement sleep: is otherwise known as dream sleep, featuring electrical activation of the brain, low muscle tone and immobile limbs, and rapid eye movements with the eyes darting around under closed eyelids. REM sleep provides energy to the brain and body and supports daytime performance. Dreams often occur during REM sleep, although they can occur at any stage.

NREM or non-rapid-eye-movement sleep, features 4 lighter to deeper sleep stages:

Stage I: this stage is light sleep, between being awake and falling asleep

Stage 2: the onset of sleep, when one becomes disengaged from the environment. Body temperature drops and breathing and heart rate become regular.

Stages 3 & 4: the deepest, most restorative sleep, in stage 4 especially characterised by the brain’s 'delta' ­waves, like ocean swells compared to the “choppy” brain waves of lighter sleep. In these stages blood pressure drops, breathing becomes slower, muscles relax and receive more blood supply, organ and muscle tissue growth and repair occurs, and human growth hormone is released. People are difficult to wake during stages 3 and 4. There is no eye movement or muscle activity. If you are awoken during deep sleep you will experience quite severe “sleep inertia”, ie you will feel groggy, disoriented and “woolly-headed” for several minutes. Some children experience bedwetting, night terrors, or sleepwalking during deep sleep.

The 2 drives that work together to get you the sleep you need are :

a) circadian drive/ 24-hr clock, and

b) homeostatic drive

What is circadian drive?

These are physical, mental and behaviour changes that occur in a 24-hr cycle, in response to light and dark in our environment.. When sun hits your retina in the morning, even through closed eyelids, the light travels from your retina to your SCN, or suprachiasmatic nucleus. The SCN sends messages to the brain and body starting up all your body’s activation processes (ie increased heart rate, blood pressure, body temperature, metabolic rate, increased attention and response rate).

What is homeostatic drive?

Homeostatic drive is like hunger (the longer between meals, the hungrier you get), ie in relation to sleep, the longer you are deprived of sleep, the more your need to sleep grows. These drives work together, so that if you have very few hours sleep or miss a night’s sleep, you can trust that your homeostatic drive will build over the lost sleep time, and you will sleep better the next night, as long as you stay awake during the day.

• Waking up during the night and then resuming sleep quite quickly, within 10 minutes, is normal {1-2 times in younger sleepers (20s-30s) ; 4-5 times in older sleepers (eg 60s, 70s) }
• Feeling drowsy after lunch is normal
• Feeling drowsy after lunch and not giving into the urge to sleep is normal.

First, it’s worth understanding that slow-wave sleep is under the control of your homeostatic drive (ie, like hunger, pressure to sleep increases the longer you go without sleep). So provided you’ve been awake during the day, building up “drive” to sleep, your brain will self-regulate to make sure your deep sleep need is met in the first half of your night’s sleep. You don’t have to do anything to make this happen. Same if you nap during the afternoon, after 20-30 minutes your brain will go into slow wave or deep sleep and start dissipating your pressure to sleep. The problem only happens when people (especially in depression) misinterpret tiredness and fatigue for need to sleep, and get into a habit of sleeping on and off during the day for a few hours at a time, then also wanting to sleep all night. The brain doesn’t get the chance to build up enough pressure to sleep at night because there’s too little waking time. This is why it’s best to cut out the afternoon naps, and build up enough pressure to sleep at night.

First, it’s true there are some reasons why electronic devices can obstruct your sleep.

1. Physiologically, the melanopsin photoreceptor in your eyes is sensitive to the blue light wavelength from your screen which suppresses Melatonin sleep hormone.
2. Attentionally, your orientation response keeps firing at the regular information/page refreshes available on social media.
3. Cognitively, the random pace of social media posting can fire your brain’s reward pathways in the same way as cocaine, and the information content can seem meaningful and valuable, so hard to turn away from.
4. Emotionally, sharing information on social media can create a rush of positive emotions like excitement and joy that you want more. Just looking up stuff can excite your curiosity and increase your sense of mastery and (Information is Power!), which feels compelling if other things in your life feel out of control.

Try to be understanding about your need for social media though. If it’s difficult to wean yourself off games or social media, remember that blaming yourself for doing something “bad” won’t help you get off it. It will just increase performance pressure on yourself to sleep without being pragmatic about the basic uncertainty of sleep onset.

Start by considering the difference between being “tired and wired” (signs of chronic insomnia) and sleepy (a sign of the objectively poor sleep quality in obstructive sleep apnoea, where the brain wakes someone even from deep sleep, to force them to breathe). You may be tired or even exhausted during the day, for a range of reasons, but not in the least sleepy. You know there’s a difference between tired and sleepy at night when you feel exhausted but are still not sleepy.

Sometimes it helps to list the possible reasons for feeling tired. Possible reasons can include:

• Medical conditions: iron deficiency; infectious diseases like glandular fever; immune disorders like Crohn’s disease or MS; ulcerative colitis; food allergies; coeliac disease; CFS/ fibromyalgia; blood disorders; heart and lung disease; COPD; restless legs; diabetes; sleep apnoea; medication side effects (especially heart, blood pressure, and pain medications).
• Psychological conditions: depression; anxiety; chronic stress; grief; boredom; eating disorders

This is not to make you more fearful or hypervigilant, but merely to start getting a balanced view of fatigue causes if you tend to only attribute your tiredness to sleep problems.

1. Low mood in the morning (may lift in the afternoon), poor concentration, fatigue, loss of interest, pleasure & motivation, increasing self-criticism, isolation and social withdrawal, feelings of hopelessness, even suicidality. See your GP if this has gone on for several weeks as these are signs of a depressive disorder.
2. Missing several nights’ sleep in a row, or missing many hours sleep each night, so that your mood becomes elevated, with increasing energy, irritability, talkativeness, distractibility, agitation, anxiety and racing thoughts. See your GP as this could be a sign of bipolar mood disorder.
3. Waking up during the night habitually, and unable to return to sleep because of chronic conditioned worry.
4. Waking up unrefreshed most days with a headache, dry mouth, and your partner saying you’re snoring. You’re unintentionally falling asleep when sedentary throughout the day. Even if you’re not overweight, ask your GP about sleep study, as this could be Obstructive Sleep Apnoea.
5. Your sleep is broken by restless leg movements, which are only improved by moving and walking around.
6. Having a delayed sleep-wake cycle (eg sleeping from 3am – 11am daily) or not having a regular sleep wake cycle, eg waking at 9am some days, then midday or later other days, and not being able to fall asleep when you want to at night. If this is happening every day, or most weekends. You feel drowsy at work all the time, and are perhaps losing work or work opportunities because of this.
7. Waking up 4-5 times during the night to pee, especially in your 20s and 30s. You could use some help with this if you’re losing confidence in your bladder capacity.
8. Waking up in a sweat with (peri)menopausal hot flushes early in the night and feeling tired and drowsy during the day.