American researchers have discovered that human brains and sleep patterns are confused by devices  that give out bright lights. Electronics, such as laptops, mislead our minds into thinking that it is still daytime, preventing sleep and increasing the risk of _ . Sleep experts say human's natural body clock begins to rest and relax from the day between 9 and 10 pm but the use of computers confuses it. A person's brain biologically becomes awake when the sun is out because bright light after dark causes the brain to stop producing the hormone   called melatonin that makes us sleepy. Researchers say blue light from devices such as iPads, which is expected to become a popular reading tool when it comes out later this month, is particularly disruptive  during the night when the brain thinks it should be dark. Experts say a good book is a far better way of resting the brain and ensuring a good night's sleep because the bedside lamp  light doesn't affect the brain as it does not look straight into a person's eyes. "Potentially, yes, if you're using an iPad or a laptop close to bedtime... that light can be stimulating   to the brain to make it more awake and delay your ability to sleep," Phyllis Zee, a professor at Northwestern University and director of the school's Centre for Sleep & Circadian Biology, told CNN. "And I think more importantly, it could also be enough to affect your circadian   rhythm. This is the clock in your brain that determines when you sleep and when you wake up. " Alon Avidan, associate director of the Sleep Disorders Center at the University of California Los Angeles, added, "I wish people would just take a boring book -- an oldfashioned book -- and read by a lamp." We can conclude from the passage that   _  .
one who uses his laptop often before bedtime can have his body clock disturbed using a laptop before bedtime is more harmful than using an iPad we'd better not do anything before going to bed the best time to go to bed is before 9 pm