Plagued by regular, long-term trouble falling asleep or staying asleep, insomniacs often feel fatigued day and night, due to their inability to get a decent quantity - and quality - of rest.
Most commonly thought of as "snoring," sleep apnea can take on different forms. Obstructive sleep apnea is snoring caused by a partial blockage of your airways as you sleep. Central sleep apnea is a neurological condition in which the brain temporarily "forgets" to tell you to breathe, so you wake up and gasp for air. Both kinds of apnea can inadvertently wake you up several hundred times a night, leaving you feeling exhausted, even though you didn't realize you were waking up.
Restless legs syndrome
A creepy-crawly feeling or uncontrollable urge to twitch or move your legs, this often misunderstood disorder interferes with many people's ability to relax and go to sleep each night. It can be brought on by hormonal changes such as pregnancy, as well as many other factors.
The most obvious characteristic of this brain disorder is the sudden, uncontrollable attack of sleep that can occur at any time of day, even during a physical activity such as walking. Most narcoleptics will suddenly nod off at inappropriate times and may have very restless nights of sleep.