Position Letter to the California Senate: AB-7, permanent Daylight Saving Time

June 3, 2019

To the Committee on Energy, Utilities, and Communications,

I write to oppose AB-7, and I hope to convince the committee that permanent DST will wake people up too early throughout the winter, restricting how much they sleep. This pattern is associated with increased cancer, heart disease, diabetes, obesity, and depression, and it is especially harmful to night owls and younger people.

I submit that this process has misunderstood recent scientific discoveries in circadian biology. The legislature must consider that “switching” is not the only harm, but instead that persistent disruption to sleep timing (called “social jetlag”) can cause health problems at all times of year. From this new perspective, people do not fully adapt to the time change, and risks to health increase when people are forced to wake up in the dark.

Considering statements made by members to the public about what science says is revealing, because scientific evidence has been used in public to say exactly the opposite of what the authors of these articles actually find.

Here are three examples from Obernolte’s petition to the U.S. Congress in 2016 (AJR 28) [1] used to justify permanent DST to California voters and to the U.S. Congress:

  • Claim: will reduce myocardial infarction from a letter in the New England Journal of Medicine, Janszky and Ljung, 2008
    Actual result: transitioning to DST increases risk by 5.1%, whereas transitioning out of DST reduces the risk by 1.5%.
  • Claim: will reduce workplace Injuries from Christopher Barnes in Journal of Applied Psychology, 2009
    Actual text: [switching to DST] “a 40-min decrement in sleep led to increased injury frequency and increased injury severity.” And also “On Mondays directly following the switch to Standard Time, in which 1 hr is gained — there are no significant differences in sleep, injury quantity, or injury severity.”
  • Claim: will reduce suicides from Berk, in Sleep and Biological Rhythms, 2008
    Actual text: “For the men…more suicides for the weeks after DLS commenced than in the weeks after it finished.”

As should be clear, the statements made in AJR 28 could be used to support permanent Standard Time, but no reasonable person would use them to support permanent DST.

These three studies are not the whole story. The science on human health and sleep is remarkably consistent: going to Standard Time in the winter is good for health, and DST is not.

For instance, considering heart attacks, Sandhu in 2014 observes a 24% increase in myocardial infarction in the spring, and a 21% reduction in the fall, within a week of the time change.

Research on four million cancer cases by a team at NIH and Harvard (Gu, 2017) shows that those on the eastern edge of a timezone (where there is more sun in the morning) get cancer at a much lower rate than those on the western side. These numbers suggest that certain cancers may increase by more than 10% by shifting the clocks by an hour the wrong direction, as AB-7 would do.

AJR 28 includes many of the same claims made to sway voters in Prop. 7, these claims now repeated in other legislatures around the world, and in the urgency statute, Sec. 2 of AB-7.

With an understanding that people do not fully adapt to their wall clocks, especially in the wintertime, many of these claims are simply false, inconsistent with the scientific research they cite and the broader literature, and must not be written into law. The legislature must take advice from the scientific community and not misrepresent the research.

It must be appreciated by the legislature that restricting sleep (as permanent DST does) creates serious health risks, that these effects persist after the time change, that these risks are greatly magnified in the winter, and that there is a wide body of literature documenting these trends. Night owls and younger people are especially vulnerable.

There are risks to human health in picking a timezone that wakes people up too early, and this legislature is proposing a harmful choice for human health. If you wish to improve human health, you must amend AB-7 to allow for more sleep in the wintertime, as Standard Time does.


Michael Herf
President, f.lux Software LLC
Los Angeles, California

[1] https://leginfo.legislature.ca.gov/faces/billTextClient.xhtml?bill_id=201520160AJR28

co-founder of f.lux, finding the connections between circadian rhythms, sleep, healthy buildings, and light. (Previously made Picasa.)

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