Falling back to standard time is healthier than springing forward

CHICAGO --- Falling back to standard time (ST) may be healthier than springing forward to daylight saving time (DST), say Northwestern Medicine sleep experts as the date for changing the clocks approaches Nov. 6. That’s because in ST, your circadian rhythms (body clock), sun clock and wall clock are in better alignment.

Still, the back and forth can wreak havoc on your body, resulting in increased risk of car accidents, heart attacks and strokes. Here Northwestern neurologists discuss the benefits of ST, and why we need to remain on a single time.

The experts:

Dr. Phyllis Zee is professor of neurology and chief of sleep medicine at Northwestern University Feinberg School of Medicine. She advocates banishing DST for better health.

Dr. Sabra Abbott is an associate professor of neurology in sleep medicine at Northwestern University Feinberg School of Medicine. 

Dr. Zee: “If you live under ST, you’re most closely aligned with your internal biological rhythms, with your physical environment (light/dark cycle) and with your social and professional times. That’s because for most days of the year, you will have more natural sunlight exposure in the morning. DST is like living in the wrong social time zone or having jet lag for half the year. 

“Light during the day helps to regulate mood, metabolism, cardiovascular function and performance, particularly in the morning hours. ST provides more morning sunlight, which is important to keep the clocks aligned for everyone, but especially for adolescents and individuals who are evening chronotypes and those with mood disorders. Bright light is activating. In addition to mood, it can affect appetite, physical activity and cognition.

“People say one-hour change is no big deal. But just that one hour in DST changes the relationship between your internal rhythm and the sun clock. Almost all body systems are regulated by circadian rhythms. These clocks exist in virtually all cells and tissues. To misalign or desynchronize them has broad implications for psychiatric and neurological health. It’s also associated with higher levels of obesity, diabetes and cardiovascular disease.   

“There are some myths out there: People think if you are in DST, the days are longer. Or, the sun sets later. But there is no actual change in daylength or sunset time relative to sun time. 

“Shifting clocks back and forth has adverse effects on the brain and body, because it causes circadian rhythms to be misaligned. Your internal rhythms are out of sync. Even with possibly an extra hour of sleep for a day in the fall, the change in time has been associated with negative performance in learning, memory and attention. There is also an increased risk of car accidents, heart attacks and strokes.”

Dr. Abbott: “When looking at the fall transition away from daylight saving time, this again raises the debate about which is better for overall health, daylight saving time or standard time. To best understand this, it helps to think of living in a world of three clocks. You have the external rising and setting of the sun, or solar clock. You have your internal clock, that generally tends to follow the solar clock. Finally, you have the wall clock, which is the time that arbitrarily changes twice a year. 

“Standard time is the time in which those three clocks are in best alignment.  Individuals who live on the far western edge of the time zone experience later sunrises and sunsets relative to clock time, mirroring what those in the eastern edge of the time zone would experience during DST. Those individuals in the western edge of the time zone tend to have greater rates of obesity, cancer and depression, thought to result from misalignment of the solar and clock time. 

“So, while you may not see acute benefits from the fall transition back to standard time (beyond possibly catching up on an hour of sleep over the weekend), we believe there are longer term health benefits from living in ST as compared to DST.”