In one campaign, French doctors used six syringes to inject 80, 000 African workers with a medicine for sleeping sickness.

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The habit can be caused by being overweight, drinking alcohol, having collapsed airways, a blocked nose, or by taking some types of medicine such as sleeping tablets before bed.

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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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