Among the conditions examined by the St Thomas' team were obstructive sleep apnoea (OSA) and restless leg syndrome (RLS).

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They also can help identify restless leg syndrome, a chronic neurological disorder often characterized by the urge to move the legs.

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According to the American Academy of Sleep Medicine, there are 81 chronic sleeping disorders, from apnea, which causes interrupted breathing, to restless leg syndrome.

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According to the agency, the same risk-benefit analysis does not hold true for restless-leg syndrome.

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