Today is the second day of Daylight Saving Time in most of North America, and I tell you, people are grumbling. Springing forward doesn’t result in many of us feeling springy right away. Shifting an hour ahead feels like spring sleep robbery. These memes heartily agree:
Despite the shock and dismay of early mornings seeming that much earlier, I really like Daylight Saving Time. It means more time in the evening for cycling, walking, swimming, dining on my back porch, and all sorts of lovely leisure-time activities done more easily with extra light. Samantha posted about the advantages for cyclists here: Daylight savings and cyclists: Yippee, yahoo, and whee!
But, what does science have to say about Daylight Saving Time (DST)? Are there health benefits to shifting daylight to later? Do people get more exercise? Better sleep? Good questions. Let’s see what I can find in the way of answers.
Some studies (like this one, done in Western Australia) suggest that the main change brought about by DST is a shift in the timing of physical activity, not necessarily an increase overall during the period. Half of the Australia study group shifted their exercise times from early morning to afternoon/evening times. Interestingly, the number of reported exercise sessions dropped (26% reported fewer sessions), but the researchers didn’t track how long the sessions lasted, either in pre-DST or during DST.
In a large multi-country study, scientists found a small (5%) increase in physical activity among European and Australian children during DST. Here’s what they said in support of DST:
Although the average increase in activity is small in absolute terms, these increases apply across all children in a population. Moreover, these small effect sizes actually compare relatively favourably with the typical effect of intensive, individual-level interventions. We therefore conclude that, by shifting the physical activity mean of the entire population, the introduction of additional daylight saving measures could yield worthwhile public health benefits.
Okay, that sounds kind of promising. And it makes sense to me– I loved being outside after supper when I was a kid, playing with my friends until darkness fell after 8pm and it was time to brush teeth, put on pajamas, read a story and go to bed. The same feeling holds true for me now, word for word.
But, I’m compelled to report that we’ve gotten only half the story here on the relative merits and drawbacks of DST. Several studies suggest that the sleep interruption caused by the one-hour shift result in a bunch of negative health effects in the population. The American Academy of Sleep Medicine published a position statement in which they advocate for a permanent standard time system (falling back and staying back).
…the acute transition from standard time to daylight saving time incurs significant public health and safety risks, including increased risk of adverse cardiovascular events, mood disorders, and motor vehicle crashes. Although chronic effects of remaining in daylight saving time year-round have not been well studied, daylight saving time is less aligned with human circadian biology-which, due to the impacts of the delayed natural light/dark cycle on human activity, could result in circadian misalignment, which has been associated in some studies with increased cardiovascular disease risk, metabolic syndrome and other health risks.
Okay, so DST is arguably less aligned with human circadian rhythms. But so is modern life under capitalism and on the internet. Am I right? AM I RIGHT?! AM? I? RIGHT?
Okay, I’ve pulled myself back together. Now, where was I? Oh, yes– the majority of the reports published by medical and public health associations recommend not springing forward and falling back, for health reasons. They suggest we (meaning our governments) pick one standard time, in particular one that best conforms to standard time.
Of course this makes a lot of sense; switching between times wreaks at least local havoc on our productivity and may have long-term effects on health. In order to be more confident of this claim, though, we’d need more evidence.
So, if you ask me what I think, here’s a thought: I always think of the spring forward/fall back time shifts as harbingers of shifts in my behaviors. I become more of an active and social and outside person come DST. I may not do as many so-called exercise sessions, but I am skipping and dipping and strolling and weeding and doing all sorts of things to celebrate the change of solar season. When it’s time to switch back in the fall, that means more indoors-focused and structured activity, which can be satisfying, too. Or, in short:
So readers, are you a DST proponent or opponent? What was your favorite after-dinner activity outside as a kid? Lemme know.
