As most individuals are aware, there is ongoing controversy over continuing the Daylight Savings Time (DST) policy generally in place in the United States and implemented in various overseas countries. This question is most pertinent to those residing in temperate zones around the globe.
The American Academy of Sleep Medicine has issued online a position statement on DST (Rishi, M.A., Ahmed, O., Perez, B.H.J., Berneking, M., Dombrowsky, J., Flynn-Evans, E.E.,… Gurubhagavatula, I. (August 26, 2020) Daylight saving time: an American Academy of Sleep Medicine position statement). They advocate for discontinuing DST.
General application of DST, in which the clocks are advanced one hour ahead with the advent of spring and then returned to standard time in the fall, has been around slightly over 100 years. One justification floated for DST has been energy savings. However, in a 24/7/365 personal and business culture, LED lighting, ongoing computer use and round the clock vehicular traffic weaken the argument that a clock advance of one hour will offer significant energy conservation.
A significant concern raised by Rishi et al is circadian misalignment. Simply stated, when we abruptly shift our external time keeping one hour ahead, there is a burden imposed on our physical and mental processing and cellular mechanisms. Normally, our body clock is synchronized with external clock cues. Our inner timekeeping is exquisitely attuned to changes in external light levels. When the clock is moved ahead and there is extra daylight in the evening, our inner clock slows its natural advance toward sleep. Surrounded by more natural illumination, people are walking their dogs later, socializing, eating and doing chores, but the clock shift could create an adverse impact on sleep onset. For example, someone who customarily goes to sleep at 10pm standard time, may, as a result of activity choices, be less tired or ready for sleep at 11pm DST, remaining awake and active beyond the time of customary bedtime preparation. The following morning, when work or school begin at 8am DST, the body and mind are still lagging behind. Any threat to the integrity of the sleep period in the 24-hour day, and restriction of sleep to below the critical 7-hour interval for adults, means potential for following day compromised working memory, and weakened executive control over focus and decision-making. The circadian mismatch with the designated clock time can invite possible immune-compromise, even if the effects are presumably short-lived as one adapts to the clock change. And one cannot assume that the psycho-biological effects of the clock change and impact on the circadian rhythm are transient inconveniences. More research on this topic is needed.
For night owl adolescents struggling to be mentally and physically ready for early middle and high school next day start times, the advanced DST clock time can interfere with the opportunity for sufficient sleep, thereby setting the stage for predictable morning struggles of sleep inertia, mental fatigue, and exhaustion. Extra minutes of nocturnal sleep on a regular basis really do make a difference for teens in terms of academic and behavioral adjustment. The customary weekday waking time in the morning, say 7am standard time, is advanced by one hour, challenging a person’s circadian alignment. Now the teen’s body and mind have to be prepared for whatever the 8am clock time demands, even though the inner time-keeper informs the adolescent that the mental and physical system is in the process of awakening. For those teens with neuro-developmental and social delays or other psychiatric impairments, the added adaptive burden in the morning can set a negative tone for the rest of the day, triggering anxiety, loss of self-confidence or fear of performance failure.
Conversely, the shift back to standard time from DST to standard time in the fall, especially in northern temperate latitudes, hastens the onset of darkness in the latter part of the day and early evening, when dependence on artificial illumination is even stronger. With higher levels of interior illumination already in place by late afternoon, during the fall and winter, there is momentum to keep lights and activity going at a significant level. Around mid-evening, when melatonin secretion naturally occurs in the pineal gland, there may be a masking of the darkness signal and a potential delay to the arrival of natural sleepiness. Individuals would need to be intentional about reducing the ambient intensity of lighting in home and office settings as the evening proceeds.
There is a growing body of health outcome research (cf. Rishi et al., 2020) to suggest that circadian misalignment related to DST can, acutely, raise the risk of motor vehicle crashes, emergency room visits, and adverse cardio-metabolic outcomes. At-risk populations include: individuals abusing substances, diabetes or other endocrine disorders, obesity, hypertension or respiratory compromise. Mood disorders are a potential downstream impact of circadian misalignment.
Clearly, maintaining a standard clock orientation throughout the calendar year represents a desirable objective from the standpoint of reducing individual and community vulnerabilities and protecting both mental and physical well-being.
Michael DeSanctis, PhD, Licensed Psychologist, Diplomate Board of Behavioral Sleep Medicine, National Register of Health Psychology Providers