RLS sensations can most closely be compared to an itching or tickling in the muscles, like "an itch you can't scratch" or an unpleasant "tickle that won't stop." The sensations typically begin or intensify during quiet wakefulness, such as when relaxing, reading, studying, or trying to sleep. In addition, most individuals with RLS have limb jerking during sleep, which is an objective physiologic marker of the disorder and is associated with sleep disruption. Some controversy surrounds the marketing of drug treatments for RLS. It is a "spectrum" disease with some people experiencing only a minor annoyance and others experiencing major disruption of sleep and significant impairments in quality of life.