Spring forward, fall back—even though the clocks change by only an hour during Daylight Savings Time, the effects can be noticeable. This is especially true in the spring, when people lose an hour of the day and that hour is often subtracted from time spent sleeping. If you’re already somewhat sleep-deprived, giving up just one hour of shuteye can negatively impact how you feel and function during the day, perhaps even compromising your alertness and reaction time while driving.
It’s as if you end up with a mild case of jet lag . Your body’s internal clock (or circadian rhythm ) may be thrown off course, which can affect how much sleep-inducing melatonin is released and when. Plus, before springing forward, it was probably light outside when you woke up, which helped your body’s internal clock activate brain regions that are involved in stimulating alertness and energy. After springing forward, you get an extra hour of light in the late afternoon but the early morning hours are dark, which means that your body’s internal clock may not be quite ready to wake up when the alarm goes off. These changes can make it harder to get going in the morning and perhaps more difficult to turn in at your usual hour.