In the other camp, proponents of permanent standard time contend that more morning light is optimal for health. Organizations such as the American Academy of Sleep Medicine, the National Sleep Foundation and the American Medical Association have endorsed year-round standard time.<\/p>\n
\u201cIt\u2019s based on the theory that early morning light is better for our overall health,\u201d Zeitzer said of these endorsements. \u201cThe problem is that it\u2019s a theory without any data. And finally, we have data.\u201d<\/p>\n
Syncing to 24 hours<\/p>\n
The human circadian cycle is not exactly 24 hours \u2014 for most people, it\u2019s about 12 minutes longer \u2014 but it can be modulated by light.\u00a0<\/p>\n
\u201cWhen you get light in the morning, it speeds up the circadian cycle. When you get light in the evening, it slows things down,\u201d Zeitzer said. \u201cYou generally need more morning light and less evening light to keep well synchronized to a 24-hour day.\u201d<\/p>\n
An out-of-sync circadian cycle has been associated with a range of poor health outcomes.<\/p>\n
\u201cThe more light exposure you get at the wrong times, the weaker the circadian clock. All of these things that are downstream \u2014 for example, your immune system, your energy \u2014 don\u2019t match up quite as well,\u201d Zeitzer said.<\/p>\n
The researchers used a mathematical model to translate light exposure under each time policy, based on local sunrise and sunset times, to circadian burden \u2014 essentially, how much a person\u2019s innate clock has to shift to keep up with the 24-hour day.\u00a0<\/p>\n
They found that over a year, most people would experience the least circadian burden under permanent standard time, which prioritizes morning light. The benefits vary somewhat by a person\u2019s location within a time zone and their chronotype \u2014 whether they prefer early mornings, late nights or something in between.<\/p>\n
Counterintuitively, people who are morning larks, who make up about 15% of the population and tend to have circadian cycles shorter than 24 hours, would experience the least circadian burden under permanent daylight savings time, as more evening light would extend their circadian cycles closer to 24 hours.<\/p>\n
Health implications<\/p>\n
To link circadian burden to specific health outcomes, the researchers analyzed county-level data from the Centers for Disease Control and Prevention on the prevalence of arthritis, cancer, chronic obstructive pulmonary disease, coronary heart disease, depression, diabetes, obesity and stroke.<\/p>\n
Their models show that permanent standard time would lower the nationwide prevalence of obesity by 0.78% and the prevalence of stroke by 0.09%, conditions influenced by circadian health. These seemingly small percentage changes in common conditions would amount to 2.6 million fewer people with obesity and 300,000 fewer cases of stroke. Under permanent daylight time, the nationwide prevalence of obesity would decrease by 0.51%, or 1.7 million people, and stroke by 0.04%, or 220,000 cases.\u00a0<\/p>\n
As expected, the models predicted no significant difference in conditions such as arthritis that have no direct link to circadian rhythms.<\/p>\n
Not the last word<\/p>\n
The study might be the most evidence-based analysis of the long-term health implications of different time policies, but it\u2019s far from the last word, Zeitzer said.<\/p>\n
For one thing, the researchers didn\u2019t account for many factors that could influence real-life light exposure, including weather, geography and human behavior.\u00a0<\/p>\n
In their calculations, the researchers assumed consistent and relatively circadian-friendly light habits, including a 10 p.m. to 7 a.m. sleep schedule, sunlight exposure before and after work and on weekends, and indoor light exposure from 9 a.m. to 5 p.m. and after sunset. But in reality, many people have erratic sleep schedules and spend more time indoors.\u00a0<\/p>\n
\u201cPeople\u2019s light habits are probably much worse than what we assume in the models,\u201d Zeitzer said. \u201cEven in California, where the weather is great, people spend less than 5% of their day outside.\u201d<\/p>\n
Moreover, though circadian health seems to favor permanent standard time, the results are not conclusive enough to overshadow other considerations. Zeitzer hopes the study will encourage similar evidence-based analyses from other fields, such as economics and sociology. \u00a0<\/p>\n
He also points out that time policy is simply choosing which clock hours represent sunrise and sunset, not altering the total amount of light there is. No policy will add light to the dark winter months.<\/p>\n
\u201cThat\u2019s the sun and the position of Earth,\u201d he said. \u201cWe can\u2019t do anything about that.\u201d<\/p>\n
The study received funding from the National Institutes of Health (grant F31HL170715).<\/p>\n","protected":false},"excerpt":{"rendered":"In the other camp, proponents of permanent standard time contend that more morning light is optimal for health.…\n","protected":false},"author":3,"featured_media":230213,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[35],"tags":[210,1141,10667,1142,3740,50,57005,1079,57006,67,132,68],"class_list":{"0":"post-230212","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-health-care","8":"tag-health","9":"tag-health-care","10":"tag-health-policy","11":"tag-healthcare","12":"tag-medical-research","13":"tag-news","14":"tag-send-to-ucomms","15":"tag-sleep","16":"tag-stanford-school-of-medicine","17":"tag-united-states","18":"tag-unitedstates","19":"tag-us"},"share_on_mastodon":{"url":"https:\/\/pubeurope.com\/@us\/115211545136995267","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/posts\/230212","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/comments?post=230212"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/posts\/230212\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/media\/230213"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/media?parent=230212"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/categories?post=230212"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/tags?post=230212"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}