Are Daylight Saving Time Changes Bad for the Brain?

Are Daylight Saving Time Changes Bad for the Brain? Beth A. Malow et al. JAMA Neurol., November 4, 2019. doi:10.1001/jamaneurol.2019.3780

Excerpts (full text, map, references, etc., in the DOI above):

Daylight saving time (DST) begins on the second Sunday in March and ends on the first Sunday in November. During this period, clocks in most parts of the United States are set 1 hour ahead of standard time. First introduced in the United States in 1918 to mimic policies already being used in several European countries during World War I, DST was unpopular and abolished as a federal policy shortly after World War I ended.1 It was reinstated in 1942 during World War II but covered the entire year and was called “war time.” After World War II ended, it became a local policy. Varying DST policies across cities and states led to the Uniform Time Act of 1966, which mandated DST starting on the last Sunday in April until the last Sunday in October. States were allowed to exempt themselves from observing DST (including parts of the state that were within a different time zone [eg, Michigan and Indiana]).

The US Department of Transportation (DOT) is responsible for enforcing and evaluating DST. In 1974, DOT reported that the potential benefits to energy conservation, traffic safety, and reductions in violent crime were minimal.2 In 2008, the US Department of Energy assessed the potential effects to national energy consumption of an extended DST and found a reduction in total primary energy consumption of 0.02%. The DOT is currently reviewing the literature associated with DST in response to a request from the US House Committee on Energy and Commerce.

Since 2015, multiple states have proposed legislation to change their observance of DST (Figure).1,2 These efforts include proposals to exempt a state from DST observance, which is allowable under existing law, and proposals that would establish permanent DST, which would require Congress to amend the Uniform Time Act of 1966.

[Figure]

State Legislation Related to Daylight Saving Time

Map of the United States depicting current practices or legislation pending as of August 2019.1,2 Note the exception of the Navajo Nation in Arizona, which participates in the daylight saving time (DST) transition. Most states have either adopted permanent DST or standard time (ST) or have legislation being considered. While Indiana does not have DST legislation being considered, it is considering legislation in which the entire state would be located within the central time zone.

This Viewpoint reviews data associated with the DST transition. The effects of permanent DST have received less attention and are beyond the scope of this review.

Clinical Implications

The transition to DST has been associated with health consequences, including on cerebrovascular and cardiovascular function. The rate of ischemic stroke was significantly higher during the first 2 days after DST transition, with women, older age, and malignancy showing increased susceptibility.3 A meta-analysis based on several studies including more than 100 000 participants documented a modest increased risk of acute myocardial infarction in the week after the DST spring transition (about 5%).4 This increased risk may be associated with the effect of acute partial sleep deprivation, changes in sympathetic activity with increased heart rate and blood pressure, and the release of proinflammatory cytokines.
The association of DST with self-reported life satisfaction scores was assessed using mixed-effect models and found to be negatively associated with individual well-being.5 The effect of DST was more significant for men and those with full-time employment. In a survey of sleep patterns in 55 000 participants, adjustments to the autumn time zone shift were easier, but adjustments were more difficult in the spring. There was a lower quality of sleep reported in participants up to 2 weeks afterwards during the spring season.6
Using time use data (eg, how individuals spent their time) in the week before and after the transition to DST, the transition to DST resulted in an average of 15 to 20 fewer minutes of sleep.1 High school students studied during the DST transition showed reduced weeknight sleep duration (approximately 30 minutes), as measured by actigraphy.7 The average sleep duration was 7 hours and 51 minutes on pre-DST transition weeknights and 7 hours, 19 minutes post-DST weeknights. In addition, longer reaction times, increased lapses in vigilance, and increased daytime sleepiness were documented. While it is important to recognize that this study only involved 40 students and was limited to the week following the DST transition, an American Academy of Sleep Medicine consensus statement has recommended 8 to 10 hours of sleep for adolescents on a regular basis.8 These recommendations were based on a detailed literature review that documented adverse effects of chronic sleep loss on attention, behavior, learning problems, depression, and self-harm. Additional studies will be needed to document whether transitions to DST have more long-term associations with adolescent sleep and contribute to adverse effects.

Genetics of Circadian Disruption

The negative health outcomes associated with the DST transition may be associated with disruptions in the underlying genetic mechanisms that contribute to the expression of the circadian clock and its behavioral manifestations in neurology (ie, chronotype).9 It is well established that genetic factors help to regulate the sleep-wake cycle in humans by encoding the circadian clock, which is an autoregulatory feedback loop. When sleep time shifts there is global disruption in peripheral gene expression, and even the short-term sleep deprivation that occurs following the transition to DST may alter the epigenetic and transcriptional profile of core circadian clock genes.10 While it is unclear how disruptive a 1-hour time change is to otherwise healthy individuals, it is possible that individuals with extreme manifestations of chronotype or circadian rhythm sleep-wake disorders, neurological disorders, or children and adolescents whose brains are still developing are more susceptible to the adverse health effects that occur following the DST transition.

Conclusions
Transitions to DST have documented detrimental associations with the brain, specifically ischemic stroke, with the risk of myocardial infarction and well-being also affected. A lower quality of sleep, shorter sleep duration, and decreased psychomotor vigilance have also been reported. Additional studies are needed to understand the causes of these detrimental effects and the role of sleep deprivation and circadian disruption. Based on these data, we advocate for the elimination of transitions to DST.