Heart attacks spike by 24% on the Monday after we "spring forward" for Daylight Saving Time.

A landmark 2014 study led by Dr. Amneet Sandhu at the University of Colorado, presented at the American College of Cardiology, analyzed hospital data from Michigan and found a 24% increase in heart attacks on the Monday following the spring time change. This spike is caused by disruption of the circadian rhythm—the body's internal clock that regulates vital functions like blood pressure and heart rate. Even a 60-minute loss of sleep can trigger increased activity in the sympathetic nervous system and higher inflammation levels throughout the body.The research examined data from over 42,000 hospital admissions across several years to confirm these trends. Notably, the study also found a 21% decrease in heart attacks on the Tuesday following the autumn "fall back" clock change. This protective effect suggests that gaining an extra hour of rest reduces physiological stress on the heart.Other major research institutions, including the Karolinska Institute in Sweden, have published similar findings in the New England Journal of Medicine. Their work shows that cardiovascular risk is highest during the first three workdays following the time transition. Together, these studies demonstrate how sensitive the human heart is to even minor disruptions in sleep and biological timing.