^ Tranah, Gregory J.; Blackwell, Terri; Stone, Katie L.; Ancoli‐Israel, Sonia; Paudel, Misti L.; Ensrud, Kristine E.; Cauley, Jane A.; Redline, Susan; Hillier, Teresa A. (2011). "Circadian activity rhythms and risk of incident dementia and mild cognitive impairment in older women". Annals of Neurology. 70 (5): 722–732. doi:10.1002/ana.22468. ISSN 1531-8249.

A catch-all term for the inability to fall or stay asleep, sleeplessness is -- as sufferers know -- a very serious problem. It's sleeplessness whenever something, whether it's physical pain, anxiety, or an underlying condition, prevents you from falling asleep within a reasonable amount of time or staying asleep long enough to achieve a good night's sleep.
Interestingly, it has been shown that the sleep-wake cycle acts on the beta-amyloid burden which is a central component found in AD.[29][30] Indeed, during waking, the production of beta-amyloid protein will be more consistent than during sleep.[29][30][32] This is explained by two phenomena. The first is that the metabolic activity will be higher during waking and thus will secrete more beta-amyloid protein.[29][30] The second is that oxidative stress will also be higher and lead to increased AB production.[29][30]

The natural internal clock that controls our 24-hour cycle of sleep and waking, circadian rhythms are easily upset by changes in schedule, and they're greatly affected by light and darkness. Jet lag is the best known circadian rhythm disorder, but this sensitive inner clock can also be disrupted by changes in routine resulting in an erratic sleep schedule.