Insomnia Disease Background

Last updated: 13 June 2024

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Introduction 

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Introduction 

Insomnia is the subjective perception of difficulty in sleep initiation, duration, consolidation, or quality of sleep, occurring despite adequate opportunities for sleep, and resulting in daytime dysfunction.

Epidemiology 

It is the most prevalent sleep disorder in the general population. Likewise in the United States (US), it is the most common sleep disorder, resulting in a substantial burden for its healthcare system. Therefore, it is an important public health problem that needs accurate diagnosis and effective treatment.  

Approximately 10% of adults have insomnia. While 30-50% of the population is affected by occasional, short-term insomnia. The prevalence of chronic insomnia is estimated to be at least 5-10% in industrialized nations and is more common in females and older adults.  

Pathophysiology 

Sleep-wake traits, such as sleep duration and timing, have genetic basis. Genes associated with insomnia include: Apolipoprotein (Apo) E4, periodic circadian regulator 3 (PER3), and the Clock gene 3111C/C Clock, among others. Molecular factors such as Orexin, catecholamines, and Histamine, which promote sleep, and γ-aminobutyric acid (GABA) Adenosine, Serotonin, Melatonin, Prostaglandin D2, which promote sleep, have all been involved as well in the pathophysiology of insomnia. For example, Orexin mediated increased neuronal firing in the wake-promoting area and inhibition of sleep-promoting areas in the hypothalamus is one possible mechanism leading to insomnia.  

Insomnia is associated with physiologic activation or hyperarousal or increased somatic, cognitive, and cortical activation. Individuals suffering from insomnia experience physiologic activation in both central and autonomic nervous systems that lead to cardiac, metabolic, hormonal changes. In turn, this activation leads to poor sleep, daytime dysphoria, increased metabolic rate, and anxiety symptoms reported by patients.    

Risk Factors 

The following are important factors in developing insomnia:

  • Increasing age: Elderly individuals must be assessed for insomnia as they report more forms of sleeping difficulty including lower rates of sleep efficiency, longer sleep onset times, increased number of nighttime awakenings, more time in bed, earlier wake up times, and more daytime naps
  • Female gender
  • Medical and psychiatric disease (eg depression, mood disorders)
  • Socioeconomic factors (eg marital strain, financial strain, unemployment)

Classification 

Short-Term Insomnia Disorder

In short-term insomnia disorder, symptoms have been present for <3 months. It is also referred to as adjustment insomnia or acute insomnia. There is the presence of insomnia with an identifiable stressor. The sleep disturbance has a relatively short duration, occurring days to weeks, and is expected to resolve when the stressor resolves or when the individual adapts. This is associated with unfamiliar sleep environment, situational stress, acute medical illness or pain, shift work, or caffeine or alcohol use. The diagnosis can only be firmly made retrospectively after it has been relieved. Short-term insomnia disorder is usually triggered by: Changes in sleep environment, high arousal states, poor sleep hygiene or short-term circadian rhythm disorders like jet lag and rotating shift work.  

Chronic Insomnia Disorder

In this insomnia disorder, insomnia has been present for at least 3 months with a frequency of at least 3 times per week. This consists of the former terms primary insomnia, secondary insomnia, and comorbid insomnia. Patients with chronic insomnia should be evaluated for depression.