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.[10] 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[11]
At the same time, it has been shown that memory consolidation in long-term memory (which depends on the hippocampus) occurs during NREM sleep.[29][33] This indicates that a decrease in the NREM sleep will result in less consolidation and therefore poorer memory performances in hippocampal-dependent long-term memory.[29][33] This drop in performance is one of the central symptoms of AD.[29]  
One factors that could explain this change in sleep architecture is a change in circadian rhythm, which regulates sleep.[29] A disruption of the circadian rhythm would therefore generate sleep disturbances.[29] Some studies show that people with AD have a delayed circadian rhythm, whereas in normal aging we will find an advanced circadian rhythm.[29][31]
Recent studies have also linked sleep disturbances, neurogenesis and AD.[29] Indeed, it is now known that neurogenesis exists and that the subgranular zone and the subventricular zone keep on creating new neurons even in an adult brain.[29][34] These new cells are then incorporated into neuronal circuits and interestingly, the supragranular zone is found in the hippocampus.[29][34] These new cells will contribute to learning and memory and will play a role in the hippocampal-dependent memory.[29]

None of these general approaches is sufficient for all patients with sleep disorders. Rather, the choice of a specific treatment depends on the patient's diagnosis, medical and psychiatric history, and preferences, as well as the expertise of the treating clinician. Often, behavioral/psychotherapeutic and pharmacological approaches are not incompatible and can effectively be combined to maximize therapeutic benefits. Management of sleep disturbances that are secondary to mental, medical, or substance abuse disorders should focus on the underlying conditions.
What to do: Talk to experts about sleeplessness, and you'll be told to practice good "sleep hygiene." What this means is that you need to take your lack of sleep seriously and look at your sleep habits and physical surroundings to see what might be preventing you from sleeping well. Start with your evening habits: What do you do in the hours before bed? Eliminate late-night eating, drinking, and computer use and your chances of falling asleep quickly and sleeping soundly are much greater. Use the last hour before bed to do things that relax you, like taking a warm bath, meditating, or reading.
Waking up in the middle of the night to use the bathroom is such a common problem it has a name: nocturia . As we get older, our bodies' ability to hold fluids for long periods decreases, thanks to a decline in antidiuretic hormones. According to the National Sleep Foundation, 65 percent of older adults have sleep deprivation resulting from waking up frequently to use the bathroom.