As the season begins to change and the winter months approach, this also means that daylight saving time is ending. When the clocks fall back, many people will welcome the “extra” hour of sleep, but the time change can also throw off our internal rhythms.
A 2020 study published in the Journal of Clinical Sleep Medicine suggests that the transition from standard time to daylight savings time, and back, incurs significant health and safety risks.
Stephanie M. Stahl, MD, associate professor of clinical medicine at the Indiana University School of Medicine, explains just how much daylight saving time affects our health and what we can do to combat it.
Question: What are the most common physical or mental health effects people experience during the transition into and out of daylight saving time?
Stephanie Stahl: People commonly lose around an hour of sleep at the transition into daylight saving time (DST), which begins in March. It can then take several days to weeks for the circadian rhythm — the internal body clock — to reset to the shift in time. The key drivers of our circadian rhythm are light and darkness. When we change to DST, the mornings are darker and the evenings are lighter, making it harder to shift our circadian rhythm to the new time.
In the few days after the change to DST, around half of people experience daytime sleepiness. Motor vehicle and workplace accidents, heart attacks, strokes, atrial fibrillation, mood disorders and suicide are all increased as well in the few days to weeks after the time change.
In the transition back to standard time, which happens in the fall, some people “gain” an extra hour of sleep. However, the circadian rhythm can still take days to weeks to adjust to the time change, during which people may still go to bed at the usual time but wake up earlier than desired. As a result, many people still lose sleep at the transition to standard time, especially if they are typically early risers.
Q: How does the time change affect different age groups, such as children, teens and adults? Are there certain groups more sensitive to the shift?
Stahl: The change to DST is more difficult for adolescents and those who normally go to bed late. The change back to standard time can be more difficult for those who wake up early. Older adults can take longer to adapt to the time change, meaning that the symptoms and increased risk of health effects may last longer.
People who are already sleep deprived are more likely to experience daytime sleepiness and increased risk of health issues.
Q: What are some practical steps individuals and families can take to help their bodies adjust more smoothly to the time change each season?
Stahl: In general (regardless of the time change direction):
- Obtain sufficient sleep, which is at least seven hours for adults, every night preceding and following the time change.
- When performing activities that require high alertness, such as driving, be extra cautious especially over the one to two weeks following the time change and remember that you should never drive if you are drowsy.
- Be sure that you are practicing additional good sleep habits, including
- Relax the hour before bedtime, so that your brain and body are ready for sleep
- Avoid high amounts of caffeine as well consuming caffeine within 10 hours of bedtime; some may need even longer
- Keep your bedroom as dark as possible during sleep
- Have a set routine for the day, including going to bed, waking up and eating about the same time every day.
How to handle the change to DST (in the spring):
- Try to make adjustments in advance to avoid sleep loss.
- At least a few days prior to the start of DST, go to bed and wake up a little earlier (10-15 minutes) each night.
- If you can’t do the above, try to sleep in a little longer on Sunday or take an early afternoon nap on Sunday for 15-20 minutes before 3 p.m.
- Head outdoors Sunday morning after the time changes. Exposure to morning sunlight helps regulate your internal clock. Continue to get sunlight exposure on subsequent mornings, if possible, to further help regulate your circadian rhythm.
- Avoid bright lights and electronics, particularly those close to your eyes, such as computers, smartphones and tablets, two to three hours before bedtime.
How to handle the change to standard time (in the fall):
- Try to make gradual changes in your bedtime and wake time at least a few days prior to the time change, if possible, by going to bed and waking up about 10-15 minutes later each day.
- If you can’t do this, try to go to bed and wake up 30 minutes later the Saturday night of the time change and then make another 30-minute change the Sunday night of the time change.
- Head outdoors in the evening for the few days before and after the time change. The light exposure in the evening can help delay the internal body clock.
- If you are waking up earlier than desired, avoid looking at screens until your intended wake up time.
Q: Some states have discussed ending daylight saving time altogether. From a health perspective, do you think that would be beneficial?
Stahl: Not only does the biannual clock change have a negative effect on our health but research has also shown that permanent DST would have negative effects, including increased risk of obesity and cardiovascular disease, due to chronic circadian misalignment.
Permanent standard time is better for sleep and overall health. Standard time aligns best with our internal body clock by having more morning light and less evening light. Arguments to keep DST are mostly non-health related, such as perceived benefits of longer evening daylight for recreation. We should put our health as the main priority. DST is essentially like waking up an hour earlier all the time (for example, 6 a.m. is 5 a.m. with DST). When asked if you want to wake up an hour earlier every day, I think most people would say no.
