The state of the science
Shifting from ST to DST has been associated with an increase in cardiovascular morbidity (heart attacks and atrial fibrillation), increased missed medical appointments, increased ED visits, increased mood disturbances and suicide risk, increased risk of fatal car crashes and medical errors – and sleep loss, said Elizabeth Klerman, MD, PhD, professor of neurology in the division of sleep medicine at Harvard Medical School, Boston.
These associations are covered in AASM statement, along with acknowledgment that most studies on the chronic effects of DST have “either been retrospective or addressed the issue indirectly.”
For Dr. Johnson, who refers to DST as “sleep deprivation time,” the most convincing data regarding the dangers of permanent DST come from studies comparing locations within time zones. “The farther you’re off from the meridian, the more you have that ‘social jet lag’ or circadian misalignment [between the innate circadian rhythm, which is synchronized with solar time, and school or work schedules],” she said at the meeting.
Researchers reported in 2017, for instance, that the risk for all cancers and many specific cancers increased from east to west within a time zone, as solar time is progressively delayed. “They documented changes in risk for every 5 degrees west from the meridian,” she said.
Dr. Johnson is a case in point of the “educational gap” that she believes needs attention. Two years ago, as chair of the sleep section of the American Academy of Neurology, she delved into the literature after the AAN asked the section whether it should endorse the AASM’s position paper on DST. “I didn’t know the literature even as a sleep scientist until I got into this,” she said.
“If you’re asked me 2 years ago,” she added in the later interview, “I would have said that permanent DST is fine.”
The sleep section recommended that the AAN endorse permanent ST, but the AAN ultimately decided it “didn’t feel strongly enough to say that standard time is unequivocally the better option,” Dr. Johnson said in an interview. “They agreed that there’s science [in favor of it], but ... it’s a big public policy decision.”
Jamie Zeitzer, PhD, associate professor of psychiatry and behavioral sciences at Stanford (Calif.) University’s Center for Sleep Sciences and Medicine, voiced similar concerns at the meeting about currently advocating a shift in either direction. It’s “absolutely clear that switching clocks, especially since it’s occurring at a population level, is deleterious and we need to get rid of it,” he said. “But before we put forth dictates on public health [with a shift to permanent ST], I think we better be sure we’re correct.”
“I think we’re getting close. I think the data thus far [are indicating] that permanent standard time is better for health,” Dr. Zeitzer said. “But I don’t think there’s a cumulative amount of evidence to really say that we have to subvert all other interests because this is so important for public health. We need at least a few more studies.”
There is not enough evidence, for instance, to conclude that the body clock does not eventually adjust to DST, he said, and it is not yet clear what roles electric light and sunlight each play in the body’s circadian time.
“And we need to think about north-south. What may be important for the upper Midwest, and for Maine, and for Washington, may not be ... good for Florida and Texas and southern California,” Dr. Zeitzer said. “You have very different patterns of light exposure, especially when it deals with seasons.”