Drinking coffee will indeed disrupt sleep. But British and American scientists found that drinking coffee will change the body clock(Body behavior) as well.
The British Medical Research Council and American Colorado University researchers confirmed that Caffeine in coffee controls and delays the Melatonin hormone, which triggers sleep.
Drinking espresso coffee before the 3 hours of sleep will delay the melatonin hormone by 40 minutes.
Caffeine will be a very helpful medicine for changing the body clock for whom having sleeping problems and for flight travelers who have Jet lag.