For example, private rooms, adopted as a standard for new hospital construction in 2006, have been shown to reduce the spread of infection and decrease the disruption of sleep, an important factor in healing.

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Is it a good or bad idea to give this supplement to kids whose sleep schedules may be thrown off by a time change or some other factor?

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On the other hand, those who aren't getting seven hours of sleep may be kept up by another condition -- anxiety, sleep apnea, or an undiagnosed illness -- that could be the real risk factor.

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"We are just starting to work out the mechanisms: hormones play a role, but a lack of physical activity, which tires you out, could well be a factor too, " said Dr Sharhad Taheri, who has studied the relationship between sleep and obesity closely.

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