Elemental Mercury Exposure and Sleep Disorder

Abstract

The sleep-wake rhythms cycle coincides with the solar 24-hour schedule. Most adult subjects in nontropical areas are comfortable with 6.5 to 8.0 hours of daily sleep, taken in a single period. It is known that normal sleep consists of four to six behaviourally and electrophysiologically (EEG) defined cycles. Sleep is divided in two main types: REM (rapid eye movements) sleep and non-REM sleep. In the general population, sleep disorders are common and usually associated with some illness, psychological and social disturbances. Insomnia as the most common sleep disorder is most often the consequence of psychological disturbances. It is characterized by the inability to fall asleep quickly. Sleepwalking, night terrors and nightmares are parasomnias which often reflect significant stress or physiopathology. Restless legs syndrome and periodic limb movements are a type of motor disorders. Restless legs usually occur before sleep onset, while periodic limb movements can fragment the sleep. Transient sleep disturbances are mostly associated with variety of factors including stress, life changes, shift work, jet lag, and some acute health disorders. The most popular drugs, such as alcohol, nicotine and caffeine, can adversely affect the quality and quantity of sleep (