I was told this earlier today and a quick search produced the following Reuters report from 2014: https://www.reuters.com/article/us-heart-daylightsaving/daylight-saving-time-linked-to-heart-attacks-study-idUSBREA2S0D420140329

This is the first paragraph of the article:

Switching over to daylight saving time, and losing one hour of sleep, raised the risk of having a heart attack the following Monday by 25 percent, compared to other Mondays during the year, according to a new U.S. study released on Saturday.

The study was led by "Dr. Amneet Sandhu, a cardiology fellow at the University of Colorado in Denver who led the study."

I don't know how to research something like this and so my question is twofold:

  1. Is the study credible?
  2. How would I find the original study?

1 Answer 1


This connection has been reported by several groups, in credible journals (I left a few references below). The study and news article you are referring to is confirming earlier findings, it is not the first to report this. In the examples I've seen, the studies rely on large datasets, for example, incidences in an entire country, in order to show a significant effect. Despite being significant, the effects are modest; that is, we are talking about fractional increases that would account for a tiny minority of acute MI over an entire year period, but is significantly greater given a current week.

Because of the marginal significance of the effects, they could be overstated due to biases in publishing significant results, but I don't see much reason to be specifically skeptical of these findings versus others. The fact that it is true for both MI and stroke in one dataset is further support it is a real effect, but since the effect is only seen on certain days of the week and those days differ between studies it could still be spurious or smaller than reported. These studies also tend to show the opposite effect on daylight savings time transitions in the other direction, so they don't necessarily support elimination of daylight savings time.

I find the best resource for finding individual studies reported in the news media is Google Scholar, scholar.google.com - if you search for the author's name, a few key words, and a year if you have it, you can likely find the original work. Some studies may be more difficult to access in full text if you don't have access to a university library, however.

Janszky, I., & Ljung, R. (2008). Shifts to and from daylight saving time and incidence of myocardial infarction. New England Journal of Medicine, 359(18), 1966-1968.

Sandhu, A., Seth, M., & Gurm, H. S. (2014). Daylight savings time and myocardial infarction. Open heart, 1(1), e000019.

Sipilä, J. O., Rautava, P., & Kytö, V. (2016). Association of daylight saving time transitions with incidence and in-hospital mortality of myocardial infarction in Finland. Annals of medicine, 48(1-2), 10-16.

Sipilä, J. O., Ruuskanen, J. O., Rautava, P., & Kytö, V. (2016). Changes in ischemic stroke occurrence following daylight saving time transitions. Sleep medicine, 27, 20-24.

  • 1
    Just to get some perspective: MIs occur less frequently on Sundays and with 30–33% increased relative risk (RR) on Mondays in working people, correlating with increased stress levels associated with returning to work (15,16). Cardiac death rates also increase by 4.65% during the Christmas and New Year’s holidays which may reflect the mental stress associated with party planning, shopping, family gatherings and added financial pressure Source
    – Narusan
    Commented Jan 9, 2019 at 6:52

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