The process from complete sleep to being alert is a very quick process considering the amount of adjustments made. To simplify; your brain shouts ‘get up now‘ and the provides some assistance, it releases stress hormones, increasing both your heart rate and your blood pressure, getting the blood around so you actually can get out of bed without collapsing onto the floor (not that it helps some people).
This normally works, once you are out of bed it doesn’t take too long for your to start functioning properly does it; however, there are some downsides to this method. Namely when you wake up at an unusually early time for you. In this case the brain isn’t easing you into consciousness so gently so all of the effects are exacerbated, blood pressure goes trough the roof and heart rates increase dramatically.
This happens to nearly everyone at least once a year, with the moving forward of the clocks. That hour-long change takes at least three days to properly adjust to, so for most people those three days are ones that at least start out as stressful. Suddenly the time is a very dangerous thing indeed, this 60 minute change increases stress hormone levels and puts so much stress on the heart that it can kill. In fact this process of waking up is the exact reason as to why people are just so likely to have heart attacks within 3 days of the clock changes.
That is how time kills.