In today's world, sleep experts often say that for a better night's rest, Americans should turn {#blank#}1{#/blank#}their smart phones or iPads before sleeping. Such electronic products make the brain more {#blank#}2{#/blank#}(act), and then influence their sleep. But according to a latest survey, more than 90% of Americans regularly use a computer or some other {#blank#}3{#/blank#} (kind) of electronic products in the hour before bed.

    Researchers find that man-made light from some electronic products at night may reduce (减少) the brain chemicals that help {#blank#}4{#/blank#} (sleep). In the study, the researchers let volunteers read, play games and watch movies on a screen for different time while measuring {#blank#}5{#/blank#} much light their eyes received. They found that two hours of {#blank#}6{#/blank#}(sit) before a bright screen at night reduced the sleep chemical levels by about 22%.

    Then the researchers studied the college students {#blank#}7{#/blank#} often used computers at night. They got the {#blank#}8{#/blank#}(similar) results. And researchers say that may not only cause sleeplessness, but also {#blank#}9{#/blank#}(raise) the risk of obesity（肥胖症）, diabetes（糖尿病）and other diseases.

    To be on the safe side, the researchers suggest that we should use computers {#blank#}10{#/blank#}(little) than before, or turn down our screens as much as possible before sleeping.