Overview of Insomnia
Insomnia is a common sleep disorder characterized by a lack of sleep or by sleep of poor quality. Insomnia, which often leads to sleep deprivation, can involve difficulty falling asleep, difficulty staying asleep (waking frequently), and/or waking up too early in the morning. There are several different causes for insomnia, suggesting that sleep is a delicate environment that is easily disrupted and that is often is difficult to obtain good sleep.
Insomnia is not a disease; rather, it is a complex symptom. This sleeping disorder is not the same as short sleep. In fact, many people sleep less than 75% of conventional eight-hour sleep time and experience no difficulty sleeping or waking.
Insomnia is divided generally into two main categories: sleep onset insomnia and sleep maintenance insomnia. Sleep onset insomnia is the inability to fall asleep naturally. Sleep maintenance insomnia is the inability to stay asleep or to resume sleep after waking in the middle of the sleep cycle. A person may experience both sleep onset insomnia and sleep maintenance insomnia, which leads to both insufficient sleep and poor-quality sleep.
Insomnia can be categorized further as acute or chronic. Acute insomnia is self-limiting, meaning it lasts for a period of time (e.g., a few weeks or months) and ends without treatment. Chronic insomnia lasts longer than 3 months and often needs to be treated.
Secondary insomnia is caused by medical problems, such as chronic pain syndromes; psychiatric problems, such as depression; or primary sleep problems, such as periodic limb movement disorder (PLMD) and restless legs syndrome (RLS). This type of insomnia is more common than primary insomnia, which is caused by life changes such as chronic stress and long-lasting emotional difficulties.
Studies have shown that people who experience insomnia have higher blood pressure during the night. Hypertension (high blood pressure) increases the risk for heart disease. More research is needed to determine the effects of insomnia on patients with cardiovascular disease.
Incidence and Prevalence of Insomnia
The prevalence of insomnia is unknown. Surveys of the general population suggest that 49% of adults report having brief periods of difficulty sleeping and about 10% of adults claim they have had insomnia lasting 2 weeks or longer. About 50% of those who have periods of insomnia also claim it is a significant problem in their lives.
Since insomnia is frequently a symptom of illness, severe stress, or trauma, incidence varies with regard to age, sex, and severity of the predisposing condition.