Daylight saving time can mess with circadian rhythms

Twice a year, most Americans experience a one-hour time shift. No matter how small it is, it can still create big problems in our daily lives. In March, we wake up exhausted and stumble out the door feeling like an hour early – only to be confused when at the end of the day it’s time to sleep, but we’re wide awake. And in November we get out of bed grateful for the extra hour zzzs standard time gave us, and then remember what it’s like to walk home in the dark.

Although more than 60 percent of Americans want this time-switching system to be abolished, we’re not there yet. Earlier this year, the Senate voted unanimously to make daylight saving time permanent, but the Sun Protection Act has yet to be voted on in the House. Meanwhile, biannual time changes cause residents of 48 states to experience circadian misalignment. This basically means that our internal clocks are wrong.

Circadian misalignment is not uncommon. Being too much of a night owl can be enough to make you misaligned. Daylight saving time can give it a boost, but so can the choices we make every day. To combat the effects of daylight saving time and other disorientations of the body clock, the key is to understand our circadian system.

What are circadian rhythms?

Our circadian system is like an internal clock that regulates sleep, wakefulness, and other cyclical behaviors, says Jean Duffy, an associate professor of medicine at Harvard Medical School. “The circadian system helps us be optimally prepared for the regular changes in our behavior that occur every day,” says Duffy. These rhythms essentially follow a 24-hour cycle: the term itself comes from the Latin phrase about a day, meaning “about a day.” For some people, especially women, the clock may be slightly off by a few minutes.

We also have other clocks that affect our bodily processes. Some lead to seasonal rhythms, others are annual, and some are even lunar, Duffy says. Most living things, down to unicellular organisms, use circadian rhythms as regulators.

How do they work?

For circadian rhythms in humans, a specific area of ​​the brain—the suprachiasmatic nucleus (SCN) in the hypothalamus—is where the magic happens. Scientists have suggested, based on studies in mice and flies, that protein accumulation is responsible for driving this mechanism. These molecules, some of which are called CLOCK proteins, come together throughout the day and activate genes that keep us awake.

CLOCK proteins can also create their own off switches. Based on research in mice and flies, CLOCK proteins cause other inhibitory proteins to slowly build up throughout the day. Finally, around dusk, these other proteins override the genes that activate CLOCK and make us sleep. The cycle continues: at night the CLOCK, which is now low, starts to increase – signaling us to wake up and start the process all over again.

Circadian rhythms are based on this feedback in our brains, but our environment also informs our clocks. “The true circadian rhythm is generated internally,” says Duffy, but external factors “synchronize our internal rhythms with the outside world.”

These external signs are called timer, which is two German terms smashed together to mean “time giver”. Light, for example, is great. Because our eyes are connected to the SCN, light exposure can be reset when these genes are activated or deactivated. Darkness can also affect melatonin production, supporting rhythmic sleep patterns by promoting the release of these hormones that make us sleepy. This may mean that the circadian rhythms of visually impaired people may not be very synchronized with our day and night schedules, although melatonin and other supplements may help. Light isn’t the only factor that affects these rhythms—exercise, age, and temperature do, too.

[Related: How to wake up when it’s still dark outside]

Our daily rhythms probably evolved because of the consistent light-dark pattern in the natural world, Duffy says. “If the first single-celled organisms lived in this strong environment of light and dark, it would help them if they could predict it,” she says.

What do they regulate besides sleep?

Quite a lot actually. Circadian rhythms affect our immune system, hormones, body temperatures and metabolism, and these are just some of the processes that have been studied. There may be many more systems driven by circadian rhythms that we haven’t even explored, Duffy says.

Metabolism is relatively well known. If you’ve ever heard that you shouldn’t eat dinner too late, the circadian system may be the reason. “If we eat during the day, our metabolic system can react quickly to that food. Whereas if we try to eat in the middle of the night, none of our systems are ready for that,” says Duffy.

Scientists are investigating how circadian rhythms affect other processes. Recently, researchers have been studying vaccine-fueled immune responses based on time of day and circadian rhythms, Duffy says.

How can we mess this up?

Drowsiness is not the only consequence of a disturbed rhythm. Individuals who go against their internal clock “are most likely to develop things like metabolic disorders, obesity, diabetes and cardiovascular disease,” says Duffy.

And it’s surprisingly easy to snap out of the madness. Even just one night of staying up late can create cascading effects. “You may sleep much longer in the morning, but not necessarily because your clock has reset, but because you’re sleep deprived,” Duffy says. “By sleeping, you miss the morning sun exposure that synchronizes your clock with the outside world. And then you don’t get to sleep so early tonight.” And then a few days later, “it’s impossible to get up because you’ve moved your clock,” she says.

Other common activities, such as talking on the phone before bed, can also confuse synchrony by mimicking the natural light we equate with the living room. Sleep is “very strongly influenced by our behavior and things we do, especially our exposure to light,” says Duffy. “So the misconception that people have is that if they’re not sleepy yet, they don’t need to go to bed yet.”

What about factors we cannot control, such as changes in the weather?

Although the time only changes by one hour in March and November, it can have some pretty serious consequences — especially the loss of an hour in the spring to daylight saving time. Researchers found that this time change caused people to lose an average of 40 minutes of sleep. It might not sound like much, but on the Monday after the time change, researchers found that workplace injuries were more frequent and severe. When gaining an hour in the fall, researchers saw no difference in injuries or sleep loss before and after the time change.

[Related: Take the best naps, with science]

Other studies have examined the increase in traffic accidents and medical errors after the spring time change. “We get up a little earlier, and that’s actually a time of day when our efficiency and alertness are at their lowest points within the 24-hour cycle. So it might make us a little more vulnerable to getting into a car accident on that day,” says Duffy.

What’s the best way to adjust to the weather change?

For some, this can happen quickly, and for others it can take a few more days, Duffy says. For those really worried about the adjustment, she advises preparing for the time change in advance by going to bed 30 minutes later on two nights in the fall (or 30 minutes earlier in the spring).

Getting enough sleep leading up to the time change is also important. “If we’re chronically sleep-deprived, it can make it difficult for us to make any kind of adjustment,” Duffy says.

And as a general rule, to keep our bodies and rhythms happy, stay regular. “Regularity appears to be important for long-term health,” says Duffy. Eating and sleeping at the same time every day can really support our circadian rhythms. Getting enough sleep is “the best recommendation we have,” says Duffy. “You’ll feel the effect much less than you would otherwise,” she says. After all, circadian rhythms know best.

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