A large dose of caffeine may be the way many of us start the day, but researchers say little and often would do more to help us stay awake. Harvard University researchers say a morning coffee boosts caffeine levels, but these fall away during the day. They say frequent low doses of caffeine would give people such as shift workers who need to stay awake more of boost. Writing in the journal Sleep, they say caffeine works by interfering with one of the systems which governs sleep. When we sleep, and for how long, is regulated by both the circadian system and the homeostatic system. The circadian system is tuned in to the difference between night and day, and promotes sleep rhythmically, with an internal clock releasing melatonin and other hormones in a cyclical fashion. But the homeostatic system is demand driven - it tells the body it needs more sleep the longer someone has been awake.
