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]  

Obstructive sleep apnea (OSA) affects around 4% of men and 2% of women in the United States.[63] In general, this disorder is more prevalent among men. However, this difference tends to diminish with age. Women experience the highest risk for OSA during pregnancy.[64] Also, they tend to report experiencing depression and insomnia in conjunction with obstructive sleep apnea.[65] In a meta-analysis of the various Asian countries, India and China present the highest prevalence of the disorder. Specifically, about 13.7% of the Indian population and 7% of Hong-Kong's population is estimated to have OSA. The two groups experience daytime OSA symptoms such as difficulties concentrating, mood swings, or high blood pressure,[66] at similar rates (prevalence of 3.5% and 3.57%, respectively).[63]

Sort of a milder cousin of sleep apnea, UARS occurs when some type of resistance slows or blocks air in the nasal passages. The most common causes are mild nasal congestion or a tongue position during sleep that blocks breathing. Because the resistance makes it harder work simply to breathe, your body is half-waking up over and over again during the night, so you don't feel refreshed in the morning.

Idiopathic hypersomnia: a chronic neurological disease similar to narcolepsy in which there is an increased amount of fatigue and sleep during the day. Patients who suffer from idiopathic hypersomnia cannot obtain a healthy amount of sleep for a regular day of activities. This hinders the patients' ability to perform well, and patients have to deal with this for the rest of their lives.[15]


Delayed sleep phase disorder is a condition where your biological clock is significantly delayed. As a result, you go to sleep and wake up much later than other people. This is more than just a preference for staying up late or being a night owl, but rather a disorder that makes it difficult for you to keep normal hours—to make it to morning classes, get the kids to school on time, or keep a 9-to-5 job.
What to do: If you suspect you have a circadian rhythm disorder, take steps to get your body onto a regular sleep schedule. Choose a bedtime and wake-up time that work for you, and follow the same routine each day, even on weekends. This can be tough for those who have to get up early during the week but like to stay up later on weekends, but do your best to craft a compromise between your work week and weekend habits. The important thing is to avoid the trap of sleeping from 10 p.m. to 6 a.m. during the week, then suddenly shifting to late nights and late mornings on the weekends. This will inevitably leave you with insomnia on Sunday night, which in turn sets you up to start the week exhausted on Monday morning.
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