Insomnia
Key Points
- Hypnotic medicines do not cure insomnia but can provide useful short-term symptomatic treatment.
- Before starting medication, the primary cause of insomnia should be investigated and treated appropriately where possible.
- Non-pharmacological approaches should be considered first line.
- Hypnotic medicines should only be used short-term (2–4 weeks); long-term regular use leads to tolerance, dependence and other adverse effects.
- Sleep hygiene, relaxation techniques and psychological methods are more appropriate than hypnotics as long-term treatment.
- Nonbenzodiazepine hypnotics (zopiclone, zolpidem, zaleplon) have similar pharmacological and adverse effects to benzodiazepines.
- Promethazine can be used for short-term management, but tolerance to its hypnotic effects can occur.
- A melatonin preparation is available for primary insomnia in those older than 55 years; it stimulates sleep initiation without causing dependence.
Definitions and Epidemiology
Insomnia refers to difficulty in either falling asleep, remaining asleep or feeling refreshed from sleep. It is the most common sleep disorder. In the UK adult population, an annual prevalence of around 35% has been reported (Ellis et al., 2012).
Insomnia is significantly associated with increasing age, female gender, comorbid anxiety, depression, and pain. By age 50, a quarter of the population is dissatisfied with their sleep, rising to 30–40% among individuals older than 65 years (two-thirds of whom are women) (Sateia and Nowell, 2004).
Pathophysiology
The pathophysiology is related to the overactivity of the arousal, emotional regulatory, and cognitive sleep systems in the brain (Riemann et al., 2015). These systems determine the degree of alertness during wakefulness and the quality of sleep.
Sleep Systems
Sleep is actively induced by neural mechanisms in the lower brainstem, pons, and parts of the limbic system. Normal sleep includes two distinct levels: Non-Rapid Eye Movement (NREM) and Rapid Eye Movement (REM) sleep.
Wake
Light Sleep
NREM
Delta/Deep
REM
NREM (80%): Stages N1–N3. N3 is the deepest (delta) sleep, primarily occurring in the first few hours.
REM (20%): Characterized by rapid eye movements, atonia (paralysis), and vivid dreams. Prominent toward the morning.
Drug Effects on Sleep Stages
- Benzodiazepines: Suppress stage N3 (deep sleep) but cause only a slight decrease in REM.
- Z-hypnotics: Shorten N1 and prolong N2, with little effect on N3 and REM.
- Sedating Antihistamines: Reduce the duration of REM sleep.
Aetiology and Clinical Manifestations
Any factor increasing arousal system activity can cause insomnia. Common causes include:
- Physical Health: Chronic pain, gastric reflux, and uncontrolled asthma.
- Mental Health: Anxiety (delays sleep onset) and depression (characterised by frequent awakenings and early waking).
- Circadian Disruption: Shift work or jet lag.
- Stimulants: Caffeine, nicotine, theophylline, and certain antidepressants.
- Withdrawal: Rebound insomnia following the cessation of alcohol or CNS depressants.
Investigations and Differential Diagnosis
Diagnosis involves identifying primary causes such as pain, psychiatric disturbances, or organic causes like sleep apnoea. It is important to differentiate clinical insomnia from "physiological insomnia," where healthy subjects (often the elderly) simply require less sleep and do not suffer from daytime fatigue.
Treatment
Non-pharmacological Therapies
These are considered first-line. Techniques include:
- Sleep Hygiene: Reducing caffeine/alcohol and optimizing the sleep environment.
- Cognitive Behavioural Therapy (CBT): Highly beneficial for long-term management.
- Stimulus Control: Limiting the bed to sleep and intimacy only.
- Relaxation Therapy: To reduce emotional and cognitive arousal.