Caffeine will get you going during the day but could leave you tossing and t

Caffeine will get you going during the day but could leave you tossing and turning at night—unless you’re a " night owl" to(26)begin with, a new study suggests.
    In the study, "morning people" who(27)consumed caffeine during the day appeared more likely than late risers to(28)awaken in the middle of their nighttime sleep.
    Fifty college students were asked to record their caffeine consumption and their sleeping and waking times for a week. The students wore(29)wrist devices that monitored their movements to(30)assess whether they had periods of wakefulness after they had fallen asleep. The researchers also(31)measured caffeine levels in the students’ saliva(唾液)over the week.
    As college students, they tended to be so(32)sleep-deprived that, for most, "it didn’t matter how much caffeine they had!" They slept well whenever they finally(33)hit the sack, said study researcher Jamie Zeitzer, an assistant professor of psychiatry and behavioral sciences at Stanford University.
    However, the more caffeine in their bodies, the more time they spent awake during the night after(34)initially falling asleep. This was not seen in the night owls.
    The amount of caffeine in a person at bedtime can vary(35)widely. Some people’s bodies clear caffeine within a few hours, but lunchtime coffee may still be in the system of other people even late at night. Therefore it’s hard to say whether any particular person could avoid the effects of caffeine on sleep by simply steering clear of coffee(or tea)in the afternoon or evening, Zeitzer said.