The 'fall back' to standard time is Sunday, but at what cost?

Pennsylvanians will turn their clocks back one hour this weekend as daylight saving time ends and standard time resumes — a ritual that marks the darker days of late autumn with a familiar mix of relief and fatigue.

While many welcome the “extra” hour of sleep, the shift can still throw off the body’s internal rhythm, said Matthew Lehrer, assistant professor of psychiatry at the University of Pittsburgh and a sleep medicine expert at UPMC.

“People have trouble taking advantage sometimes of the extra hour, because their body's still waking them up,” Mr. Lehrer explained. “Your biological processes, your internal clock, are still synchronized to the environment and to the light-dark cycle.”

The chemical that controls waking — cortisol — is tied to a person’s regular sleep routine and, as