Daylight Saving Time Disrupts Your Body: It’s Not Harmless

The upcoming time change will take place during the night of March 28–29, 2026, inevitably shifting our sleep patterns. This policy, introduced for economic reasons, remains controversial, particularly because of its health effects.

Time Change and Sleep: An Immediate Disruption of the Circadian Rhythm

For about a decade, researchers have been conducting studies to understand the effects of the biannual clock change. Their findings converge: this one-hour shift acts as a stress on the body, with consequences sometimes underestimated. The time change directly disrupts the internal clock, also known as the circadian rhythm. It regulates essential functions such as the cycle of waking and sleeping, but also body temperature and hormonal secretion. According to a study from the Medical University of Vienna(1), this transition leads to desynchronization between the biological clock and social time.

Practically, the switch to daylight saving time is the hardest to absorb. According to a 2024 study conducted at Cologne University Hospital(2), individuals lose an average of 60 minutes of sleep in the days that follow. This loss is not trivial. It is accompanied by a sleep debt that can last several days. Moreover, sleep disturbances increase markedly. Difficulties falling asleep, nocturnal awakenings or fragmented sleep are frequently observed. The body typically takes about two days to adapt, though this duration can be longer for vulnerable individuals, particularly teenagers and night-shift workers.

Time Change: Effects on the Brain, Attention, and Vigilance

Beyond sleep, the time change impacts cognitive abilities. The disruption of circadian rhythms alters how the brain functions. A 2020 study from the University of Chicago found that in the days following the switch to daylight saving time, cognitive performance declines. This shows up as difficulties with concentration, reduced working memory, and more errors. These effects are comparable to those seen with jet lag, which is why researchers use the term “social jet lag.”

This cognitive fatigue also has real-world consequences in daily life. A study highlights a decline in productivity linked to fatigue induced by the time change. Put differently, sleep deprivation isn’t just personal discomfort—it also affects professional performance.

Time Change and Cardiovascular Health: An Underestimated Risk

The effects of the time change don’t stop at the brain. They also involve the cardiovascular system. Several studies show an increased risk of heart events after the switch to daylight saving time. A British study published in February 2026 in the European Journal of Epidemiology found that the risk of a myocardial infarction rises by 40% on the Monday following this change. This spike is explained by a combination of sleep loss, physiological stress, and hormonal disruption.

This phenomenon is not isolated. Other research confirms a rise in hospital admissions for heart problems in the days that follow. The body, subjected to a brutal shift, struggles to maintain its internal balances, particularly in blood pressure and heart rate. People already vulnerable, such as those with cardiovascular disease or sleep disorders, are especially exposed. In them, adaptation can be slower and the consequences more pronounced.

Visible Consequences for Safety and Daily Life

The effects of the time change also appear in very concrete situations, particularly on the road. A Mayo Clinic study in the United States(5), conducted in 2023, shows a 6% increase in traffic accidents in the days following the switch to daylight saving time. Fatigue and reduced vigilance explain much of this. Drivers, less attentive, react more slowly. The gap between the biological clock and social time plays a key role here.

More broadly, the time change disrupts daily habits. Waking up earlier when the body isn’t ready, going to bed without feeling enough fatigue: these imposed adjustments generate a form of stress. This misalignment, described by researchers as “social jet lag,” can last several days, and longer for some people.