As the calendar flips to November, we’re on the cusp of daylight saving time coming to an end on the 5th, prompting us to turn our clocks back by one hour.
Despite the benefit of gaining an extra hour of sleep, this change is not without its consequences. Health complications, particularly a short-term spike in heart attack rates, have been noted with the onset of daylight saving time in spring, but even the autumn adjustment is not entirely benign.
Our physiology is inherently resistant to even minor shifts in routine. A study from Finland in 2016 highlights a temporary 8% rise in ischemic stroke occurrences—the most prevalent stroke type caused by an obstructive blood clot—immediately following the daylight saving shift. This study showed that individuals above 65 years were at a 20% greater risk, although this heightened risk subsided after a couple of days.
The reason seems to lie in the disruption of our circadian rhythm, which is the natural internal clock governing our daily cycles. Martin Young, PhD, from the University of Alabama at Birmingham, suggests that our bodies require approximately a day to recalibrate for each hour of time change, similar to jet lag. However, the syncing rates vary among our internal clocks, with the heart’s clock notably slower to adjust, causing a temporary misalignment between our body’s organs during the transition.
Interestingly, this one-hour shift has contrasting effects in different seasons. Research in the BMJ journal found a 24% hike in heart attack risk following the spring forward but a 21% decrease after falling back to standard time, possibly linked to the extra sleep people get.
Another consequence as daylight saving ends is an uptick in car accidents due to earlier nightfall, heightening driving risks. Despite nighttime driving constituting only a fraction of our total driving time, it is responsible for half of traffic-related fatalities.
Even with the additional hour we ‘gain,’ Natalie D. Dautovich, PhD, from Virginia Commonwealth University and the National Sleep Foundation, says the sleep timing shift can cause temporary daytime sleepiness and concentration issues akin to jet lag.
On the brighter side, Dautovich notes that earlier daylight can aid in realigning our circadian rhythm with the new schedule.
Mood disorders, particularly depression, also tend to surge after the shift from daylight saving to standard time, as a Danish study discovered. With a notable 8% rise in depression diagnoses following the time change, Søren D. Østergaard, MD, PhD, emphasizes that the dark and cold days ahead can have a uniformly negative psychological impact.
To ease into the transition, Dautovich advises gradually postponing bedtime and waking time by 15 minutes before the change. She recommends minimizing bright light and screen use before bedtime, while maintaining a dark sleeping environment in the morning.
Young emphasizes the role of environmental and behavioral cues like light, exercise, and food in resetting our internal clocks. He advocates for a morning routine that combines these elements to help synchronize the body’s various internal timekeepers.
