Heart Attacks Rise 24 Percent After the Spring Clock Change
After the fall change, when people sleep more, hospital counts drop 21 percent.
Talks at Google · Why We Sleep: Science of Sleep & Dreams | Matthew Walker | Talks at GoogleHospitals record 24 percent more heart attacks in the days after the spring clock change, and 21 percent fewer after the fall change.
Matthew Walker, a sleep scientist at UC Berkeley, describes daylight saving time as a global experiment involving 1.6 billion people in 70 countries twice a year. In spring, clocks move forward and people sleep less. In fall, clocks move back and people sleep more.
An hour can feel too small to matter. The numbers suggest even one lost hour of sleep may make the heart more vulnerable.
Questions people ask
When do the extra heart attacks happen?
The change appears in the days right after the spring clock shift, when the population sleeps less. Researchers compare heart attack counts on those days with the same weekdays in surrounding weeks. The pattern reverses after the fall shift.
How could one lost hour affect the heart?
Short sleep raises blood pressure and stresses the cardiovascular system, and it can disrupt blood sugar. The clock change is useful for study because almost everyone shifts sleep at once, which makes a small individual effect visible across millions of people.
Are these only serious heart attacks?
Yes. The percentages come from hospital records, so they count heart attacks serious enough to bring people to the hospital. Chest pain treated elsewhere would not be included in those counts.