^ Hirshkowitz, Max (2004). "Chapter 10, Neuropsychiatric Aspects of Sleep and Sleep Disorders (pp 315-340)" (Google Books preview includes entire chapter 10). In Stuart C. Yudofsky; Robert E. Hales (eds.). Essentials of neuropsychiatry and clinical neurosciences (4 ed.). Arlington, Virginia, USA: American Psychiatric Publishing. ISBN 978-1-58562-005-0. ...insomnia is a symptom. It is neither a disease nor a specific condition. (from p. 322)
Restless leg syndrome (RLS) is an overwhelming need to move the legs. This urge is sometimes accompanied by a tingling sensation in the legs. While these symptoms can occur during the day, they are most prevalent at night. RLS is often associated with certain health conditions, including ADHD and Parkinson’s disease, but the exact cause isn’t always known.
The most common sleep disorder is insomnia. Others are sleep apnea, narcolepsy and hypersomnia (excessive sleepiness at inappropriate times), sleeping sickness (disruption of sleep cycle due to infection), sleepwalking, and night terrors. Management of sleep disturbances that are secondary to mental, medical, or substance abuse disorders should focus on the underlying conditions.
Primary sleep disorders are most common in men and women over the age of 65. About half of the people claim to have some sleep problem at one point. It is most common in the elderly because of multiple factors. Factors include increased medication use, age-related changes in circadian rhythms, environmental and lifestyle changes  and pre diagnosed physiological problems and stress. The risk of developing sleep disorders in the elderly is especially increased for sleep disordered breathing, periodic limb movements, lestless legs syndrome, REM sleep behavior disorders, insomnia and circadian rhythm disturbances.
What to do: This condition requires evaluation by an otolaryngologist, who can look at your nose, mouth, and throat to see what's interrupting your breathing and how to repair that process. You'll also need a sleep test in which your oxygen levels are measured. Often, the first treatment doctors will recommend is a Continuous Positive Airway Pressure (CPAP) device, a specially designed nasal mask that blows air directly into your airways. Studies have shown CPAP masks to be extremely effective in treating sleep apnea. However, many people don't like wearing them -- and, of course, it doesn't work if you don't wear it.
Sleep apnea, obstructive sleep apnea, obstruction of the airway during sleep, causing lack of sufficient deep sleep, often accompanied by snoring. Other forms of sleep apnea are less common. Obstructive sleep apnea (OSA) is a medical disorder that is caused by repetitive collapse of the upper airway (back of the throat) during sleep. For the purposes of sleep studies, episodes of full upper airway collapse for at least ten seconds are called apneas
Even if you’ve struggled with sleep problems for so long that it seems normal, you can still learn to sleep better. You can start by tracking your symptoms and sleep patterns, and then making healthy changes to your daytime habits and bedtime routine. If self-help doesn’t do the trick, you can turn to sleep specialists who are trained in sleep medicine. Together, you can identify the underlying causes of your sleeping problem and find ways to improve your sleep and quality of life.
Although we do not know the causual relationship, we know that the more the AD progresses, the more we find sleep disorders. In the same way, the more sleep disorders there are, the more the disease progresses, forming a vicious circle. Taken this into account, sleep disturbances are no longer a symptom of AD and relationship between sleep disturbances and AD is bidirectional.
Although the exact mechanisms and the causal relationship between sleep disturbances and AD are not yet clear, these findings already provide a better understanding. In addition, they open up ideas for the implementation of treatments to curb the cognitive decline of patients suffering from this disease. In the same way, it also makes it possible to better target at risk population.
Keep a pen and paper next to your bed. If you're often kept awake by racing thoughts and worries and you tend to make to-do lists in your head, keep a pen or pencil and a small pad of paper handy and write them down. As you put each item down on paper, imagine yourself setting aside that concern. (Again, use a book light; don't turn on the overhead or a bright bedside light to write.)