A normal person needs eight hours of sleep every night. A person who speaks in sleep is called a Somniloquent. A sleep walker is known as Somnambulist. Sleep patterns change as one gets older. Also, older people may have multiple medical problems, they may be taking many medicines that could be interfering with one's sleep.
Sleep apnea is another most commonly found sleep disorder suffered by elders.
REM - Rapid eye movement. Difficulty with normal breathing patterns during sleep.