Antonio Rinaldi points me to a press release describing a recent paper by Amneet Sandhu, Milan Seth, and Hitinder Gurm, where I got the above graphs (sorry about the resolution, that’s the best I could do).
Here’s the press release:
Data from the largest study of its kind in the U.S. reveal a 25 percent jump in the number of heart attacks occurring the Monday after we “spring forward” compared to other Mondays during the year – a trend that remained even after accounting for seasonal variations in these events. But the study showed the opposite effect is also true. Researchers found a 21 percent drop in the number of heart attacks on the Tuesday after returning to standard time in the fall when we gain an hour back.
Rinaldi thinks: “On Tuesday? No multiple comparisons here???”
The press release continues:
“What’s interesting is that the total number of heart attacks didn’t change the week after daylight saving time,” said Amneet Sandhu, M.D., cardiology fellow, University of Colorado in Denver, and lead investigator of the study. “But these events were much more frequent the Monday after the spring time change and then tapered off over the other days of the week. It may mean that people who are already vulnerable to heart disease may be at greater risk right after sudden time changes. . . . We know from previous studies that a lack of sleep can trigger heart attacks, but we don’t have a good understanding of why people are so sensitive to changes in sleep-wake cycles. Our study suggests that sudden, even small changes in sleep could have detrimental effects,” he said.
Rinaldi also found this news article:
The researchers found no difference in the total weekly number of PCIs performed in 2010 to 2012 during the spring time changes (week before, 661; week after, 654; P=.87) and fall time changes (week before, 610; week after, 652; P=.25).
However, the RR for MI was higher on the Monday after the spring time change compared with other Mondays (RR=1.24; 95% CI, 1.05-1.46) and lower on the Tuesday after the fall time change compared with other Tuesdays (RR=0.79; 95% CI, 0.62-0.99).
Analyzing all 365 days is more work, but hard work is what research is all about. I agree with Rinaldi that “the Tuesday after returning to standard time” is a funny comparison to pick out. It could make sense but, if so, I think it would show up in other weeks, not just after daylight savings.