"If you want your spouse to listen and pay strict attention to every word you say, talk in your sleep."

Anonymous

This is defined as periods of sleep loss that occur for at least three nights per week for one month or longer. Chronic insomnia can be caused by various different factors acting on their own or in combinations. These factors may occur along with other health problems.

Insomnia associated with psychiatric, medical or neurological disorders
Psychiatric disorders are a common source of chronic insomnia, however they account for less than 50 percent of cases. Anxiety and mood disorders are the most common psychiatric conditions that are associated with insomnia. Insomnia is also associated with a wide range of medical and neurological disorders.
Factors that cause problems throughout the day such as pain, immobility, breathing difficulties, dementia, and hormonal changes associated with pregnancy or menopause can also cause insomnia. Many medical disorders worsen at night such as asthma or acid reflux which is worsened by lying down.

Insomnia associated with medication and substance use
A variety of prescription drugs and non-prescription drugs can lead to wakefulness and poor-quality sleep. Some drugs, legal and non-legal, that are commonly related to insomnia include:
Caffeine
Nicotine
Alcohol
Stimulating antidepressants
Steroids
Some over the counter cold and flu remedies
Beta blockers, and
Recreational drugs such as ecstasy, amphetamines and cocaine

Insomnia associated with specific sleep disorders
Insomnia can be associated with specific sleep disorders including:
Sleep apnea
Restless legs syndrome (RLS)
Periodic limb movement disorder (PLMD)
Circadian rhythm sleep disorders such as jet lag

Primary Insomnia
When other causes of insomnia have been investigated and ruled out, difficulty with sleep may be classified as primary insomnia. Factors such as chronic stress, hyper-arousal and behavioral conditioning may be contributors to Primary Insomnia.
Sleep patterns do alter as we get older with older, people tending to sleep more lightly. As our bodies age our quality of sleep becomes poorer and becomes lighter, less efficient and less restful.Your physician or other practitioner may prescribe insomnia medication to help you get to sleep, commonly known as sleeping tablets.