A. Insomnia is the most common sleep disorder. It involves difficulty falling asleep, staying asleep, or waking up too early and not being able to return to sleep, leading to daytime impairment. B. OSA insomnia is not a recognized standalone disorder; obstructive sleep apnea (OSA) and insomnia are separate conditions, though they can co-occur. C. Circadian rhythm sleep disorders are less common and involve disruptions in the timing of sleep, such as shift work disorder or delayed sleep phase disorder. D. Restless leg syndrome is a neurological condition that can impact sleep but is not as prevalent as insomnia