5 ways to protect your health post-DST
Deep dive: How DST affects our health and what you can do about it
Dear community,
The switch to daylight savings time (DST) was just observed in the US this past weekend — and many of us are feeling its effects. Before we dive into why and what we can do about it, a note about frequency: starting this month, we’ll be moving to twice monthly posts. This will enable me to release each post when it’s ready and spend time on a book project (more to come!).
It turns out that three-quarters of the world’s population does not observe the biannual switch between DST and standard time — including India and the Philippines, two countries I spent time in as a child — along with much of the rest of Asia, Africa, Latin America, and the Caribbean.
So it was always jarring to me to do this in the US, both as a kid (ages 6 to 10) and when I returned as an adult. Of note: Within the US, Hawaii, parts of Arizona, American Samoa, Puerto Rico (where I am right now — to give a keynote), Guam, the Northern Mariana Islands, and the US Virgin Islands don’t observe this custom, either. The rest of the US does.
What are the roots of DST?
DST was first introduced in the US by President Wilson in 1918 on the tail end of World War I as a way to extend daylight and conserve fuel, modeled after Germany and other European powers. But it proved unpopular and was abolished by Congress federally, though it remained a local option. It was next reinstated as a year-round policy (called “war time”) by President Wilson during World War II, from 1942 to 1945. The twice-yearly clock change, with DST occurring only during the summer, started in the following year, with local variations in timing until the Uniform Time Act standardized DST across the country in 1966.
Fun fact: Centuries prior, Benjamin Franklin wrote a satirical letter in 1784 proclaiming that waking people up earlier in the summer — thereby creating more sunlit evening time — would be a great way to save on evening candle use. It didn’t catch on.
By the way, the commonly held idea that farmers like DST turns out to be incorrect — farmers have lobbied against DST since its inception, as their work follows the sun’s rhythms and is disrupted.
“As in 1917, when the U.S. first adopted daylight time as a war measure, farmers were the loudest objectors. The cow, they cried, is a delicately balanced creature, yields less milk for defense when her hours are disturbed. The dew, they insisted, stays on the grass until 9 a.m. (10 a.m. daylight saving time), and farmers cannot work their fields until the dew dries. Rising before dawn, they declared, they would be dog-tired long before day's end.”
—1942 TIME article on DST
During medical training, ‘falling back’ often meant working an extra hour during an already stressful night or 28-hour shift. And ‘springing forward’ to DST? A lost hour of much needed sleep. But the impacts actually go much further: The week following either time switch carries an increased rate of errors in medicine, by about 19% for DST and about 5% for the standard time switch.
The science says: DST — compared to standard time — desynchronizes our internal circadian rhythms from those of the sun, because we lose morning sunshine hours (we wake up to darker mornings) and gain exposure to brighter evenings (the sun sets ‘later’ in the day).
This is the opposite of what our brains and bodies need. We do best with early morning sunlight and darker evenings. Our internal clocks are set by well-timed exposure to sunlight and darkness, acting in part through a hormone called melatonin (suppressed by light and active in the dark, triggering us to sleep) — in addition to other cues like food, physical activity, and social inputs.
Exposure to early morning light coinciding with our awakening (ie: when sunrise is closer to our wakeup times) and to darker evenings (when sunset is a few hours prior to bedtime) is optimal for our circadian functions.
DST makes it so we take longer after rising to achieve optimal alertness (and associated functions) and on the other end, are unable to go to sleep ‘on time,’ given the extra evening light exposure, which suppresses melatonin and other sleep-regulating systems — but still have to wake up early (earlier than ideal for our internal clocks). In technical terms, DST induces “phase delay,” so our internal circadian clock, set by the sun, is off-cycle — later — relative to the time by the clock. These effects are particularly felt in Western-most areas of any time zone, because the sun already rises and sets at a later time by the clocks there.
Our circadian systems is intrinsically tied to a number of essential functions, not just our sleep, but also our metabolic processes, our hormones, our immune systems, and our moods and cognition. This why you may be feeling ‘off’ on a number of levels.
Here’s how DST affects our health:
The DST switch results in altered molecular signaling and gene expression, including in the genes governing our internal clocks and sleep, stress responses, functioning of the heart, immune and inflammatory systems, and several hormonal cascades.
Chronic circadian misalignment increases inflammation and stress reactivity, while decreasing parasympathetic nervous system tone (which helps us rest and digest), with increased heart rate and lower heart rate variability — all setups for acute cardiometabolic events and potentially longer-term health risks.
Every year, in the days immediately after DST goes into effect, we see an increase in acute events like heart attacks, cardiac arrests, strokes (particularly for women, those over 65 years, and those with cancer), and the heart arrhythmia atrial fibrillation (particularly for women). Heart attacks have been observed to fall during the transition back to standard time.
Depression increased by 11% in a study in Denmark in the 8 weeks post-DST. The change to DST has also been associated with an increase in acute or emergency visits, as well as return visits (within 4 days of the first visit). We also see an acute increase in the rate of fatal car accidents by 6% in the week post-DST.
After a few weeks, car crashes actually decrease, presumably because of brighter evening driving conditions, by one estimate by 18% over eight weeks post-DST.
What’s the economic impact?
Aside from its health impacts, DST acutely decreases worker productivity and increases workplace injury — by one estimate, DST costs the US $434 million every year. (But that extra hour of evening light is profitable for certain key lobbies, including leisure goods and services, sporting goods and events, gas stations and convenience stores — central to why it persists.)
Here’s the bottom line:
“There is evidence that the body clock does not adjust to DST even after several months. Permanent DST could therefore result in permanent phase delay, a condition that can also lead to a perpetual discrepancy between the innate biological clock and the extrinsic environmental clock, as well as chronic sleep loss.”
—American Academy of Sleep Medicine’s position statement on DST
Many public health groups, including the American Academy of Sleep Medicine, have issued statements against moving to permanent DST given the myriad health impacts — and instead support instating permanent standard time. Luckily, in the US, permanent DST didn’t gain favor in the House in 2022, though Congress might reconsider this question. When that happens, urge your Congresspeople to consider standard time instead.
(Mexico actually did choose standard time as their permanent option in 2022 — so stay tuned for studies on medium and longer-term impacts from this policy change.)
What can we do about it?
So what does all this mean for us now, in the days to come? How can we best counteract the effects of the DST switch on our health? (This is a light version of what I do when I cross 10-12 time zones from India or the Philippines to the US and back.)
1. Honor your internal clock. If your schedule allows, fall asleep and stay asleep at the times most comfortable for your body (synced to the rhythm of the sun — ie ignore DST) — and try to keep this similar across most days. Expose yourself to morning sunlight, preferably outdoors (windows and windshields block UV light). If you wake up or start work or school before sunrise, use a dawn simulator or bright light therapy. At night, dim the lights and try to stay off screens at least a couple of hours before bed. Consider using blue light-blockers to minimize the brain-awakening effects of evening light, including outside.
2. Physical activity. As routines permit, consider getting in a walk or workout at the beginning of your day — ideally outside so you give your body multiple ‘wake up’ cues at once. This will help with regulating stress, metabolic processes, energy, sleep, cognition, and mood.
2. Emphasize anti-inflammatory nutrition. Knowing that these weeks may induce extra inflammation as your body settles into DST, take extra care to choose foods that help decrease inflammation. Reach for whole grains over white or processed items; plenty of fruits, vegetables (frozen or fresh!), nuts, healthy fats, and lean proteins; and water most of the time over soda, juice, or alcohol.
4. Connection. Connection is a hugely helpful antidote to systemic dysregulation — make the extra effort to stay connected to those who are important to you, either in person or remotely. Post-DST, there’s a tendency with later sunsets to also elongate our social engagements and push back our bedtimes — try to curb this, since getting those crucial hours of sleep every night is extremely stabilizing.
5. Be in the moment. Practices that ground us and help us be present are also key for reducing the impacts of stress, inflammation, and metabolic dysregulation. That might take the form of laughter, yoga or meditation, art, music, a spiritual practice, gratitude journaling, or something else —whatever works best for you.
Be gentle with yourselves and each other as we all adjust to this paradigm over the next few weeks. The DST switch can indeed be rough physiologically — so keep that in mind if you feel more reactive or stressed, and give yourself time to adjust.
How are you each doing and what’s worked for you in riding out DST?
Wishing you light,
Dr Devika Bhushan
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