The deadly hazard of Daylight Savings Time

Last month, we “sprung forward” and lost an hour of time when advancing the clocks. Even though this happened a month ago, I still feel compelled to write about it because according to a new study, this dubious practice can take a serious toll on your health.

The main reason for changing the clocks is that it supposedly saves energy. It gives us an extra hour of daylight during spring and summer so you can you can wait an hour longer before turning on the lights in the evening. But the next morning, we have to turn on the lights an hour earlier to avoid stumbling around in the dark. So how does that save any energy or money?

In my view, this myth of “conserving energy” is more about politics than science.

According to some accounts, Benjamin Franklin first thought up the idea of daylight savings. Ironically, Franklin also advised, “early to bed, early to rise.” But during daylight savings time, the early riser has to rise in the dark. So I’m not completely convinced we have Franklin to thank for this odd ritual.

Regardless of who originated it, the practice of changing the clocks stuck around through WW I, as it gave an extra hour of daylight at the end of the day to continue training the ill-prepared troops. Then, after WW II, recreational facilities liked the extra daylight so they could extend sports activities in the summer season.

And I remember when I was in high school, President Richard Nixon extended “daylight savings time” to start earlier and end later in the year in a largely symbolic effort to save energy. But I also remember not having enough energy going to school in the dark in the morning.

Which brings me back to the real reason I’m writing about this topic today. The fact is, daylight savings time negatively impacts your health. It basically gives the whole country jet lag, simultaneously, twice a year. And this leads to problems on the roadways and in the workplaces. It also leads to health problems…

New study connects daylights savings to stroke

In a new study, Finnish researchers reviewed 10 years’ worth of data on 12,000 people from 2004 to 2013. They found the national incidence of stroke rises by eight percent over the two days following daylight savings time transitions, whether the clocks were turned forward or back. And adults older than 65 years were 25 percent more likely to suffer a stroke during those two-day periods.

I was not surprised when I saw this good, solid study came out of Finland. The Finns often study topics others ignore. In fact, while I was a researcher at the National Institutes of Health, we worked with Finnish researchers and published a number of good studies in the “new” arena of diet, nutrition, body size, and health.

In terms of the twice-per-year, two-day spike in strokes, it’s hard to imagine what other factor could be involved. Daylight savings time does affect the normal circadian rhythms of the body that happen over every 24 hours, largely in response to light and darkness. Insomnia and shift work can also disrupt these cycles, which in turn can affect blood circulation and blood pressure.

Overall, I believe many natural forces impact health. In fact, last December in my Insiders’ Cures newsletter, I reported on a study linking strokes with certain weather patterns.

Some remain skeptical about these associations. They say the only way to really know is to stop changing the clocks and see whether the eight to 25 percent surges in stroke no longer happen.

I say give it a try and stop fooling around with our clocks.


  1. “Does daylight saving time increase risk of stroke?” Science Daily ( 2/29/2016