How Sleep Is Affected By Time Changes

What Difference Could an Hour Make?

By Michael J. Breus, PhD, D, ABSM
WebMD Weight Loss Clinic - Feature

Reviewed By Stuart Meyers

This Sunday at 2 a.m., the daylight-saving time change will force most of us to spring forward and advance our clocks one hour. This effectively moves an hour of daylight from the morning to the evening, giving us those long summer nights. But waking up Monday morning may not be so easy, having lost an hour of precious sleep and perhaps driving to work in the dark with an extra jolt of java. How time changes actually affect you depends on your own personal health, sleep habits, and lifestyle.

Moving our clocks in either direction changes the principal time cue light -- for setting and resetting our 24 hour natural cycle, or circadian rhythm. In doing so, our internal clock becomes out of sync or mismatched with our current day-night cycle. How well we adapt to this depends on several things.

In general, "losing" an hour in the spring is more difficult to adjust to than "gaining" an hour in the fall. It is similar to airplane travel; traveling east we lose an hour. An "earlier" bedtime may cause difficulty falling asleep and increased wakefulness during the early part of the night. Going west, we fall asleep easily but may have a difficult time waking.

How long will it take you to adapt to time changes?

Though a bit simplistic, a rule of thumb is that it takes about one day to adjust for each hour of time change. There is significant individual variation, however.

How will you feel during this transition?