Getting a good night’s sleep can be a challenge for many. Indeed, it is estimated that around one in three people regularly experiences insomnia, with older people particularly at risk.¹

We spend around a third of our lives sleeping. Newborn babies need up to 17 hours per day, while teenagers need eight to 10 hours, and adults need seven to nine hours. A night’s sleep typically occurs in four to five cycles, with each lasting 90-120 minutes, divided into REM (rapid eye movement) and non-REM (NREM) sleep. NREM is further sub-divided into three stages, recently renamed N1, N2 and N3 (see below). Sleep is slightly skewed, in that we get more NREM during the first half of the night and more REM during the second half.

• N1 is the shallowest stage and lasts just a few minutes as we are falling asleep. Our heart rate and breathing slow, our muscles relax and our eyes move slowly. Brain activity involves low amplitude theta waves. 
• N2 is light sleep and makes up the largest cumulative portion of our slumber. Our heart rate and breathing slow further, our body temperature falls and our eyes stop moving. Brain activity is marked by sleep spindles and K-complexes. 
• N3 is the deepest stage when we are hardest to rouse, with our heart rate and breathing at their slowest and no eye movements. Delta waves predominate, while the body takes this opportunity to repair cells and tissues and strengthen our immune system. 
• Finally, Stage R involves rapid eye movement (during phasic REM but not tonic REM), more-rapid heart rate and breathing, muscle paralysis and increased brain activity including dreaming. 

For most people, stage R begins around 90 minutes after falling asleep and lasts 10 minutes first time round, increasing with each cycle to 30-60 minutes just before we wake.

Hormones linked to our circadian rhythm include: growth hormone (higher during sleep), melatonin (higher during sleep), thyroid-stimulating hormone (TSH; higher during sleep and lower in the afternoon), cortisol (rising rapidly in the middle of the night and peaking next morning), and ghrelin and leptin (which promote and suppress the appetite respectively).²

Initial insomnia, broken sleep or early morning wakening can occur de novo or in the context of chronic pain or psychiatric illnesses like depression or mania. For the former, where attention to sleep hygiene does not work, cognitive behavioural therapy (CBT) or non-benzodiazepine hypnotics such as melatonin may help. Benzodiazepine hypnotics are a last resort and used with caution. Obstructive sleep apnoea (OSA) involves intermittent occlusion of the airway at night causing the patient to wake up repeatedly. First-line treatment may include a continuous positive airway pressure (CPAP) machine. Other treatable sleep disorders include restless leg syndrome (RLS) and narcolepsy. 

However, for most of us, a good night’s sleep rests on good sleep hygiene practices, which include daily exercise and timely exposure to natural light, limiting nap time, avoiding too much caffeine or food before bedtime, limiting screen time in the hour before bed and a warm, dark, quiet and comfortable bedroom environment.