Oct 29: Turning the clocks back an hour each fall can feel like a gift: an extra hour of sleep. But the tradeoff is less daylight in the evening, and the annual switch continues to earn mixed reviews. The same is true in spring, when we lose an hour as daylight saving time begins.
But this twice-a-year reset isn’t so easy for our internal clocks – also known as our circadian rhythm. In fact, desynchronization of our body clocks has been linked to increased health risks such as depression, obesity, heart attack, cancer, and even car accidents.
In 1997, my laboratory discovered the CLOCK gene – the first circadian gene in mammals. My colleagues and I determined that mutated CLOCK genes can cause delays in circadian functions, which in turn lead to dysfunctions in metabolic, behavioral, and cognitive abilities.
Every cell in our bodies keeps track of the time, and changes in daily patterns can trigger stress in our brains and cause sleep deprivation, disorientation, and memory loss. It can also lead to difficulties with learning, social interactions, and overall cognitive function.
In 2016, in collaboration with Dr. Masashi Yanagisawa’s laboratory, we discovered the first genes in mice that regulate sleep using an unbiased mutagenesis and screening method. We uncovered two genes in mice that control how much rapid eye movement (REM) sleep and non-REM sleep are needed. A healthy sleep pattern should include long stretches of non-REM sleep, when the brain is not actively dreaming and processing memories.
With this knowledge, we can begin to understand why sleep is important for our health and how to improve sleep hygiene for the 15% to 20% of people in the U.S. with sleep disorders – particularly when environmental factors disrupt our health.
While there is still a lot of uncharted territory in the field of circadian rhythms and sleep medicine, there is a growing body of evidence to suggest that spring-forward, fall-back is not the best choice for the 21st century.
LISTEN: Dr. Takahashi joins The New York Times podcast “The Argument” to discuss Daylight Saving Time.
How daylight saving time can disrupt our health
Sleeplessness is commonly associated with stress, and the last six years have been among the most stress-filled years in recent memory. It’s likely that more people were struggling with sleep deprivation than was reported during the COVID-19 pandemic. Having to readjust once again is bound to be another hurdle for people in the U.S.
Add this to standing facts – 26% fewer third-shift than first-shift workers report getting enough sleep, and teens and tots typically get far less than their recommended 10 hours nightly due to demanding school, sports, and social schedules – and daylight saving time seems to be exacerbating an already prevalent issue.
Low mood and depression
Sleep disruptions can also cause an increased risk of mental illness. In the fall, losing an hour of evening light can markedly affect our mood – and signal the beginning of seasonal affective disorder, a type of depression that is associated with a lack of sunlight.
Darkness = Sleepy + grumpy
Lack of sunlight suppresses the production of two important hormones: sleep-inducing melatonin and the “happy chemical” serotonin, which plays a key role in mood balance. In other words, we’re more likely to be grumpy and tired – but unable to fall asleep – in the days following daylight saving time.
One study showed that hospitals reported addressing 11% more depressive symptoms right after the fall time change. The time change in the spring did not produce a similar result, supporting the notion that sunlight does our minds and bodies good.
Cardiovascular risks
Multiple studies have shown a small increase in heart attacks after the start of daylight saving time in the spring and a small decrease at its end in the fall. Meanwhile, stroke rates are 8% higher in the first two days following both time changes.
Vehicular crashes
Fatal traffic accidents also become more of a danger after the spring time change. A recent study showed that fatal accidents increase 6% and are more common in the mornings directly after the clock change. There did not appear to be an effect from the fall-back transition to standard time.
Of course, one season of time changes is highly unlikely to cause issues. However, over time, we must be mindful of how sleep, or lack thereof, affects our overall health. While we can’t manually reset our internal clock, try these tips to have a more restful daylight saving transition this year.
