It is a hot debate (but also sleepy) that ignites twice a year in the United States: why do we still change clocks? The “spring in front” each March can be particularly volatile, the research connecting this loss of a precious time of sleep to more heart attacks and fatal car accidents. Now a new study published today in the journal PNA Indicates that sticking to standard time can improve health.
Three time policies
While many people support the end of these seasonal time changes, disagreements persist on the policy to adopt – you compose in standard time all year round or implementing permanent summer time.
“You have passionate people on both sides, and they have very different arguments,” said Dr. Jamie Zeitzer, co-author of the study and circadian physiologist at Stanford Medicine, in a press release.
Supporters of the permanent hour of daylight say that more evening light could save energy, dissuade crime and give people more free time after work. According to Zeitzer, golf courses and outdoor shopping centers are the great supporters of this policy. However, a test of permanent writing time of daylight in 1974 proved to be so unpopular that it was abandoned after less than a year. In 1986, the duration of the day -to -day saving time was finally increased from six months to seven months and invoices offering a permanent savings time were also introduced to the congress since 2018. However, none of these measures has been adopted.
Supporters of permanent standard time argue that more morning light is better for our health. Organizations such as the American Academy of Sleep Medicine, the National Sleep Foundation and the American Medical Association approved the standard time all year round.
“It is based on the theory that light early in the morning is better for our overall health,” said Zeitzer about these endorsements. “The problem is that it is a theory without any data. And finally, we have data.”
[ Related: All the ways daylight saving time screws with you. ]
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In the study, a team from Stanford Medicine compared three different time policies: permanent standard time, the permanent summer of daylight and the biannual displacement that we are currently making. They compared the way the three affect people’s health and circadian rhythms, the innate body clock that regulates several bodily functions.
According to the results of the team. The use of permanent standard time or permanent daylight would be healthier.
However, permanent standard time also seems to benefit most people. By modeling exposure to light, the circadian impacts and the county health characteristics by the county, the team estimates that the use of permanent standard time (and not from the front in March) could prevent some 300,000 cases of stroke per year. In comparison, the permanent summer time of daylight would reach around two thirds of this same effect.
“We have found that staying standard or staying in summer time is certainly better than changing twice a year,” said Jamie Zeitzer.
For sleep studies, it is also important to remember that the human circadian cycle is not exactly 24 hours. For most people, it looks more like 24 hours and 12 minutes and light can change this cycle. The light in the morning accelerates the circadian cycle, while the evening light slows things. According to Zeitzer, we generally need more morning light and less evening light to stay synchronized with 24 hours day and a circadian cycle excluding synchronization was associated with a range of bad health results.
“The more you get an exposure to light in bad times, the lower the circadian clock. All these things that are downstream – for example, your immune system, your energy – do not correspond as well,” said Zeitzer.
To study the exposure to light in each time cycle, the team used a mathematical model based on sunrise and local sunset and its effect on the circadian load. The circadian burden is essentially the way in which the innate clock of an individual must change to follow the day 24 hours a day.
More than a year, they found that most people would suffer the least circadian load in permanent standard time, which prioritizes morning light. The advantages of this low circadian burden vary depending on geographic location in a time zone and if they prefer mornings at night.
In addition, the 15% of the population considered as main elements have circadian cycles which are shorter than 24 hours. These people would experience the least circadian burden under a time of permanent savings, because the evening light would bring their circadian cycles closer to 24 hours.
Time health results
To take a closer look at specific health results and circadian charges, the team used centers for Disease Control and Prevention on the prevalence of arthritis, cancer, chronic obstructive disease, coronary diseases, depression, diabetes, obesity and brain vascular accidents. They were particularly interested in the rate of stroke and obesity, because these conditions are both influenced by circadian health.
According to their models, the permanent standard time would reduce the national obesity prevalence by 0.78% and the prevalence of the stroke by 0.09%. However, these slightly low percentage changes would represent approximately 2.6 million people less with obesity and 300,000 cases of the stroke less.
Under permanent daylight, the national obesity prevalence would decrease by 0.51%, or 1.7 million people. Stroke would decrease 0.04%, or 220,000 cases.
The models have predicted any significant difference under conditions such as arthritis which have no direct link with circadian rhythms.
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No policy will make it brighter in winter
Although this study has provided concrete examples whose policy should be implemented for better health, there are still unanswered questions and different variables to consider. The team did not take into account several factors that could influence an exposure to real light, including weather, geography and human behavior.
In their calculations, the researchers assumed coherent and relatively circadian light habits, but many people have much more erratic sleep hours and spend more time inside in reality.
“People ‘luminous habits are probably worse than what we assume in the models,” said Zeitzer. “Even in California, where time is great, people spend less than 5% of their day outside.”
Although circadian health seems to promote permanent standard time, the results are not enough to overshadow other considerations. However, Zeitzer hopes that this type of research will encourage analyzes based on similar evidence of other areas, such as economics and sociology.
Above all, time policy is simply to choose clock hours represent sunrise and sunset. It does not change the total quantity of light, and no policy will add light to these dark winter months.
“It’s the sun and the position of the earth,” said Zeitzer. “We can’t do anything about it.”
