The results of the study suggest that people with iRBD are more likely to report having a first-degree relative with the same sleep disorder than people of the same age and sex that do not have the disorder. More research needs to be conducted to further understand the hereditary nature of sleep disorders. A population susceptible to the development of sleep disorders includes 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. The results indicate that individuals who experienced a TBI are most disproportionately at risk for developing narcolepsy, obstructive sleep apnea, excessive daytime sleepiness, and insomnia. The studys complete findings can be found in the table below:

Sleep disorders and Neurodegenerative Diseases
Neurodegenerative diseases have often been associated with sleep disorders, mainly when they are characterized by abnormal accumulation of alpha-synuclein, such as multiple system atrophy (MSA), Parkinsons disease (PD) and Lewy body disease (LBD). For instance, people diagnosed with PD have often presented different kinds of sleep concerns, commonly in regard to insomnia (around 70% of the PD population), hypersomnia (more than 50% of the PD population), and REM sleep behavior disorder (RBD) - that may affect around 40% of the PD population and it is associated with increased motor symptoms.
A sleep disorder, or somnipathy, is a medical disorder of an individuals sleep patterns. Some sleep disorders are severe enough to interfere with normal physical, mental, social and emotional functioning. Polysomnography and actigraphy are tests commonly ordered for diagnosing sleep disorders. Sleep disorders are broadly classified into dyssomnias, parasomnias, circadian rhythm sleep disorders involving the timing of sleep, and other disorders including ones caused by medical or psychological conditions. When a person struggles to fall asleep and/or stay asleep with no obvious cause, it is referred to as insomnia, the most common sleep disorder. Others include sleep apnea, narcolepsy and hypersomnia (excessive sleepiness at inappropriate times), sleeping sickness (disruption of sleep cycle due to infection), sleepwalking, and night terrors. Sleep disruptions can be caused by various issues, including teeth grinding (bruxism) and night terrors. Management of sleep disturbances that are secondary to mental, medical or substance abuse disorders should focus on the underlying conditions.Primary sleep disorders are common in both children and adults. However, there is a significant lack of awareness in children with sleep disorders, due to most cases being unidentified. Several common factors involved in the onset of a sleep disorder include increased medication use, age-related changes in circadian rhythms, environmental changes, lifestyle changes, pre-diagnosed physiological problems, or stress. Among the elderly, the risk of developing sleep disordered breathing, periodic limb movements, restless legs syndrome, REM sleep behavior disorders, insomnia, and circadian rhythm disturbances is especially increased. List of conditions
There are a number of sleep disorders.