In addition, insomnia may be a symptom of underlying sleep disorders. For example, restless legs syndrome—a neurological condition in which a person has an uncomfortable sensation of needing to move his or her legs—can lead to insomnia. Patients with restless legs syndrome typically experience worse symptoms in the later part of the day, during periods of inactivity, and in the transition from wake to sleep, which means that falling asleep and staying asleep can be difficult. An estimated 10 percent of the population has restless legs syndrome.