Why daylight saving time may be bad for your brain and health
October 29, 2020
On Sunday, Nov. 1, we will turn our clocks back an hour to end daylight saving time. While the "fall back" technically equates to a potential extra hour of sleep, the reset isn't so easy for our internal clocks – also known as our circadian rhythm.
In fact, this twice-a-year 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 is 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 such as daylight saving time disrupt our health.
The daylight saving time debates
As scientists at UT Southwestern and around the world continue to delve into the effects of daylight saving time, the topic continues to spark debates in legislative circles, too.
In Florida, for instance, two senators recently introduced a bill called the Sunshine Protection Act, which would keep the U.S. on daylight saving time through Nov. 7, 2021, because, they state, “Americans are already dealing with enough change and other disruptions from the COVID-19 pandemic.” (The legislation appears to be stalled in Congress.)
Permanent daylight savings time; however, is not recommended by the scientific community. Studies have shown that residing on the most western border of time zones, which is similar to being on daylight savings time, is associated with increased risks for cancer. Rather permanent standard time is the optimal solution.
The European Union voted in spring 2019 to do away with the biannual time changes next year, and several other U.S. states are considering similar legislation – largely because of the health risks posed by time changes twice a year.
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.
Our internal CLOCKs
More than 20 years ago, Dr. Joseph Takahashi and his colleagues at UT Southwestern set out on a daring scientific journey to successfully pinpoint a mammalian clock gene using an unbiased method of gene discovery. Their work continues to reveal important findings.
How daylight savings can disrupt our health
Sleeplessness is commonly associated with stress, and 2020 has been among the most stress-filled years in recent memory. It's likely that more people are struggling with sleep deprivation than are reported during the ongoing 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 recommend 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
In the fall and winter, many people typically spend all day indoors at work or school – or home, amidst the pandemic. By the time we leave our tasks, it’s dark already. This means we get less exposure to the sun, which reduces the amount of vitamin D our bodies produce. Low levels of vitamin D are linked to low mood and depression, as well as fatigue, muscle pain, and weakened bones.
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 result in a similar result, supporting the notion that sunlight does our minds and bodies good.
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.
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.
Tips to manage daylight saving time transitions
1. Make a gradual shift
A few days before the time changes, go to bed and wake up 10 to 15 minutes later each day to help your body slowly adjust.
2. Stick to your sleep schedule
Once the clock changes, try to keep things as normal as possible. Get up and go to bed at your normal times. The same goes for your other daily routines, such as eating and exercising.
3. Maintain good sleep hygiene
A healthy bedtime routine can do wonders for your sleep. A few good sleep hygiene habits to follow include going to bed and waking up a the same time every day; not watching TV or browsing social media; avoiding caffeine and alcohol in the evening; and not exercising before going to bed.
4. Get out in the sun
Spending time outdoors during daylight hours, even if it’s only for a quick walk over lunch, can help stimulate your body. You also can sit by a window or try light therapy.
5. Limit your caffeine intake
You don’t have to skip your morning cup of coffee, but try not to go overboard if you hit an afternoon slump. And definitely stay away from caffeinated beverages in the evening so you can fall asleep when you should and stay asleep.
Get help sleeping
UT Southwestern’s Sleep and Breathing Disorders Clinic is among the most advanced sleep centers in the nation. To visit with a sleep medicine expert, call 214-645-5337 or request an appointment online.
Keeping your circadian rhythms in sync
The fall time change, when you gain an hour of sleep, is thought to be an easier adjustment than springing “forward” in March, but many scientists believe any disruption of the optimal phasing of our circadian rhythms – the timing of our rhythms relative to the phase of the solar day-night cycle – can be a culprit in associated health risks.
Organized efforts to “lock the clock” and “ditch the switch” have gained traction in recent years. But daylight saving time remains a fixture in about 70 countries, including the U.S., where it was first introduced in 1918 and later formalized by The Uniform Time Act of 1966.
For now, there are no large-scale changes on the horizon, so we must “spring forward” and “fall back” to the best of our abilities. Understanding that daylight saving time disrupts our circadian rhythms is a start. And knowing that help is available for sleep deprivation or disorders is the key to coping with the condition.