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16 Ways Daylight Saving Could Affect Your Health, According to Science

24/7 Wall St. logo 24/7 Wall St. 11/1/2018 Hristina Byrnes

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Daylight saving time was introduced during World War I as a way to conserve fuel needed for war industries and to extend the working day so people could use less energy. The resulting sleep disturbance, however, can take a toll on your body and wreak havoc on your internal clock.

Opinions are mixed when it comes to the time changes twice a year, as well as the potential impact on public health. In fact, Arizona (except the Navajo region), Hawaii and the overseas territories of the United States don’t observe DST, and some states have petitioned to permanently end it. Reasons cited vary from getting more sun, to altered sleep patterns and increased road accidents.

Experts point to several possible causes for the troubles, including trouble adjusting to the sudden sunset time change.

To compile the following list of health effects DST may have on a person’s health, 24/7 Wall St. reviewed over a dozen studies and consulted a sleep expert.

Click here to see the ways DST could affect your health.

The most common time-change disorder is circadian rhythm disorder, a disruption in the body’s internal clock due to DST or jet lag, according to Dr. Jordan Stern, board certified in Otolaryngology and Sleep Medicine and founder of Blue Sleep. “Moving the clock forward is always more difficult; in travel this translates into more difficulty when traveling east than when traveling west.”

Adapting to new time zones usually takes the body about one day per hour of time difference, but some studies show effects lasting up to 10 weeks. Other research goes even further, indicating that the circadian system does not adjust to DST at all, and its seasonal adaptation to shorter days and longer nights is disrupted by the introduction of summer time. The result is your body follows one clock while your social calendar follows another.

The one-hour change can seriously impair cognitive and motor function, especially in sleep-deprived populations, said Stern. Because natural blue light is the strongest factor in controlling the internal clock, rising 15 minutes earlier for four days, and turning on blue light (from your computer or phone in the morning) will definitely help wake you up in the morning, he added. “For falling asleep at the right time a few days before DST hits, 2 mg of melatonin (not more!), two hours before bedtime can help.” Warm baths, chamomile tea, and reading a book are other helpful strategies for winding down at night, Stern added.


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1. Stroke hospitalizations increase

Changing the clock -- both in the spring and fall -- has been associated with an increase in stroke hospitalizations in the following two days. The overall rise was 8% in that period. Women were more susceptible to the time changes than men. The risk was also higher for cancer patients and people over the age of 65.


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2. People spend even more time online

Believe it or not, it is possible to be even more addicted to the internet. This has become an obstacle to productivity, leading to "cyberloafing," which is described as engaging in non-work online activities while working. The shift to DST has been shown to result in a dramatic increase in cyberloafing behavior, according to a study published in the Journal of Applied Psychology.


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3. The fall shift mostly affects people under 65 years old

The effects of the time changes were consistently more noticeable in people under 65 years of age than in those who were older, according to the study published in the New England Journal of Medicine.


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4. More people seek help for depression

Researchers in Denmark looked into the records of more than 185,000 patients at the Danish Psychiatric Central Research Register from 1995 to 2012. They compared the trend in the incidence of hospital contacts for unipolar depressive episodes following the clock shifts to and from summer time. The transition from summer time to standard time was linked to an 11% increase in depressive episodes that lasted for about 10 weeks. The time shift in the spring was not associated with a parallel change.


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5. Suicide rates among men rise

The one-hour shift due to daylight saving correlated with an increase in male suicide rates in the weeks after summer time takes effect in March, according to an Australian study published in the Sleep and Biological Rhythms journal. Also, suicide rates in the weeks after DST ended remained significantly higher compared to the rest of the fall season, the study noted. The authors suggested that even small changes in the body's natural rhythm could be destabilizing for vulnerable people.


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6. Cluster headaches are more likely

The most likely times for these painful headaches that occur in clusters were associated with the number of daylight hours, according to the American Headache Society. The periods of intense headaches slow down about two weeks after the start of DST in the spring and its end in the fall.


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7. People are prone to car accidents

Getting even an hour less sleep in the fall when we turn the clocks back has been linked to an increase in traffic accident rates. An analysis reviewing data from 21 years of fatal car crashes in the United States shows a significant increase in the number of accidents on the Sunday of the shift back to standard time, possibly due to late night or early Sunday morning driving after consuming alcohol and feeling sleepy. A separate study by British Columbia's Ministry of Transportation and Infrastructure found a 10% increase in the average number of crashes in the late afternoon up to two weeks after DST ends. Driving in the dark has been pointed out as a possible factor.


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8. Heart attack rates go up after the time shift in the spring and down in the fall

Researchers examined the incidence rate of acute myocardial infarctions (AMI), more commonly known as heart attacks, for weeks after the spring and fall DST changes between March 2010 and September 2013. The Monday after DST starts in the spring was linked to a 24% increase in heart attacks; however, the Tuesday following the return to standard time in the fall was associated with a 21% reduction. Another study came to similar conclusions. The rate of heart attacks significantly increased in the first three weekdays after the spring transition, affecting more women. In the fall, however, the incidence rate was lower, affecting more men.


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9. Sleep may be affected for up to a week

The cumulative effect of five consecutive days of waking up earlier as a result of the fall daylight saving change is a net loss of sleep across the week, according to a review in the Sleep Medicine Reviews journal. It usually takes the body one day per hour change to get accustomed to the time shift, Stern said. "The first day of time change, everybody will have difficulty falling asleep at the new time when we are moving the clock (in the fall), and be sleepy in the morning."


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10. Immune system improves for four days after the fall transition

What a difference just an hour of sleep can make! Researchers from Cornell University reviewed up to 3.4 million Behavioral Risk Factor Surveillance System (BRFSS) respondents from the United States and 160 million hospital admissions from Germany over one decade. Setting the clocks back an hour improves population health for about four days after DST ends, because people slept about an hour more, according to the study. There is not enough evidence to suggest the same or the opposite is true following the shift in the spring.


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11. High school students do worse on SATs

If you can help it, don't take the SAT the day after DST starts in March. It adversely affects sleep and vigilance in high school students, which leads to daytime sleepiness, deteriorated vigilance, and increased lapses. A study published in the Journal of Neuroscience, Psychology, and Economics found a strong negative relationship between the time shift and SAT scores.


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12. People with children report low life satisfaction when DST begins

Research examining the effects on a person's well-being by the spring and fall transitions in the U.K. and Germany has found that people experience deteriorations in happiness levels in the first week following the beginning of summer time. The negative effects are particularly strong, according to the study, among people with young children at home.


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13. Miscarriage rates are higher after DST starts in the spring

Researchers from Boston University Medical Center studied the impact daylight saving time has on pregnancy loss rate among women who have undergone in-vitro fertilization. They found that miscarriage rates were significantly higher in the first three weeks after DST takes effect in the spring and among women who had already had a prior pregnancy loss. The study, published in Chronobiology International, found no difference in pregnancy loss rates during the change back to standard time in the fall.


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14. Both waking up and falling asleep are problematic

The brain's circadian rhythm, or internal clock, follows daylight. "The blue light from natural daytime light is the most powerful signal for our 24-hour body rhythm," Stern said. However, he added, each cell in the body has its own rhythm, and when there is a sudden change in time such as jet lag or DST, normal body functions are immediately affected.


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15. Insomniacs have a harder time with DST

People already suffering from insomnia may find DST changes even more difficult to deal with, Stern said. Just one night of irregular sleep can trigger a pattern of insomnia. Common symptoms include feeling fatigue during the day, worrying about sleep, cognitive impairment, mood swings and lack of energy, according to the American Academy of Sleep Medicine.


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16. Changing to DST increases workplace injuries

Studies examining data from the National Institute for Occupational Safety and Health covering the 1983-2006 period show mining workers sustain more workplace injuries as well as more severe wounds on Mondays following the switch to DST. Data from the Bureau of Labor Statistics show workers sleep on average 40 minutes less on Mondays than other days following the time shift.


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