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]
Although we do not know the causual relationship, we know that the more the AD progresses, the more we find sleep disorders.[29] In the same way, the more sleep disorders there are, the more the disease progresses, forming a vicious circle.[29] Taken this into account, sleep disturbances are no longer a symptom of AD and relationship between sleep disturbances and AD is bidirectional.[30]
A population susceptible to the development of sleep disorders is people who have experienced a traumatic brain injury (TBI). Because many researchers have focused on this issue, a systematic review was conducted to synthesize their findings. According to their results, TBI individuals are most disproportionately at risk for developing narcolepsy, obstructive sleep apnea, excessive daytime sleepiness, and insomnia.[20] The study's complete findings can be found in the table below:

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.