Every spring, millions of Canadians set their clocks forward one hour on the night of the second Sunday in March - in 2026, this switch to Eastern Daylight Time takes place on the night of Saturday March 7 to Sunday March 8. While most people perceive this change as a mere temporary nuisance - a day when we feel a little more tired - sleep science and cardiovascular medicine document real and sometimes serious biological effects that go far beyond the subjective impression of missing an hour's rest. Understanding these effects means we can adapt our behavior to minimize the impact on our health and that of our loved ones.
The debate over the abolition of daylight saving time is alive and well in Quebec and North America - several U.S. states have already passed legislation to maintain daylight saving time year-round, and the Quebec government has initiated discussions on the subject, in coordination with neighboring provinces and states to avoid time discrepancies within the same integrated economic zone. In the meantime, Quebecers continue to suffer the physiological disruption of the time change twice a year. This article presents the scientific data on the impact of Daylight Saving Time, along with practical advice based on sleep medicine on how to get through this period with as few undesirable effects as possible.
The circadian rhythm: why losing an hour's sleep is not insignificant
The circadian rhythm is the internal biological clock that regulates wakefulness and sleep cycles over a period of around 24 hours. This central clock, located in the suprachiasmatic nucleus of the hypothalamus, synchronizes thousands of physiological processes - hormone secretion, body temperature, blood pressure, carbohydrate metabolism, immune functions, mood - on a day-night cycle. Melatonin, synthesized by the pineal gland in response to darkness, is the main hormonal signal of this system: its secretion triggers drowsiness in the evening and prepares the body for sleep.
The spring time change creates an artificial mismatch between the internal clock and social time - the body thinks it's 6 a.m. when the alarm goes off at 7 a.m., and it's dark at what was, biologically, 10 p.m.. This circadian misalignment - comparable to a one-hour internal jet lag to the East - disrupts melatonin secretion, fragments sleep, reduces its effective duration, and disrupts the regulation of many physiological systems dependent on the circadian cycle. For the majority of healthy people, full adaptation takes five to seven days - but for those already suffering from sleep disorders, seasonal depression, anxiety or chronic illness, the effects can be more pronounced and long-lasting.
Cardiovascular risks, accidents and mood disorders: what the research says
Epidemiological studies published in cardiology journals document a significant increase - of the order of 24 % - in the number of hospital admissions for myocardial infarction in the days following the switch to spring daylight saving time. This transient increase is attributed to the combination of acute sleep deprivation, increased physiological stress linked to circadian rhythm disruption, and the direct cardiovascular effects of sleep deprivation - elevated blood pressure, increased sympathetic tone, reduced heart rate variability, activation of coagulation. Switching to standard time in autumn - which adds one hour of sleep - is associated with a slight reduction in cardiovascular events.
Neurologically and behaviorally, an increase in road accidents has been documented in the days following the spring time change - increased daytime sleepiness and reduced alertness increase the risk of driving errors. Mood disorders, particularly in people predisposed to SAD or major depressive disorder, may be exacerbated by sleep disruption and altered evening exposure to natural light. Children and teenagers - whose sleep requirements are higher than those of adults, and whose circadian rhythms are naturally shifted to later hours - may experience particularly marked difficulties in concentration, irritability and school performance in the week following the time change.
Practical medical advice to help you adapt to the 2026 time change
The most effective strategy for minimizing the impact of the spring time change is gradual advance adaptation, initiated several days before the change. Starting on the Wednesday or Thursday before the time change - i.e. March 4 and 5, 2026 - we recommend gradually advancing bedtimes and rising times by 15 to 20 minutes a day, so that by the time of the change on Sunday March 8, the body is already partially adapted to the new schedule. This gradual approach is particularly beneficial for young children, the elderly and those with pre-existing sleep disorders.
Exposure to natural light from the moment you wake up is the most powerful intervention for rapidly resynchronizing the circadian rhythm - open the shutters immediately, have breakfast in a bright space, go for a walk outside in the early hours of the morning. Conversely, limiting exposure to blue light from screens - telephone, computer, tablet - in the two hours before bedtime encourages the natural secretion of melatonin and makes it easier to fall asleep. Avoiding caffeine after 2 p.m. in the week of the time change, limiting alcohol - which fragments sleep despite its initial sedative effect - and maintaining regular physical activity in the morning or early afternoon all contribute to circadian adaptation. A short nap of no more than 20 minutes in the early afternoon may be useful for very tired people, but a long or late nap will delay sleep in the evening.
Frequently asked questions about the time change and health
My child is very difficult to wake up in the morning after the time change - is this normal?
Yes, it's perfectly normal and well documented physiologically. Children and teenagers have circadian rhythms that are naturally shifted towards later hours - they tend to fall asleep later and want to get up later - which makes them particularly vulnerable to the switch to Daylight Saving Time, which requires them to wake up even earlier, biologically speaking. For school-age children and teenagers, it's particularly useful to anticipate the change as early as Thursday or Friday, by gradually bringing their bedtime forward, making sure their bedroom is dark enough to encourage early sleep, and organizing immediate light exposure as soon as they wake up. The disruption generally lasts one to two weeks for children, before returning to normal.
I'm taking sleeping pills or benzodiazepines - do I need to adjust my medication during the time change?
As a general rule, it is not necessary to change the dosage of sleeping pills or benzodiazepines simply because of the time change. Medication prescribed at a fixed time should be taken according to the time on the clock - if you take a sleeping pill at 10 p.m., you take it at 10 p.m. according to the new time. If you experience unusual sleep disturbance in the week following the time change and are taking sleep medication, it's best to consult your doctor rather than adjusting the dosage yourself. People taking medications for chronic conditions whose efficacy depends on precise timing - insulin, anticoagulants, certain hormone treatments - should discuss with their doctor or pharmacist the best way to adjust their dosing schedule.
Does the time change really worsen heart risks, or is this exaggerated?
The epidemiological data are real and have been replicated in several countries and contexts - the increase in hospitalizations for heart attacks in the days following the switch to daylight saving time is a phenomenon documented in studies involving hundreds of thousands of patients. That said, it's important to contextualize: this increase is transient and of modest magnitude on a population scale. At the individual level, the additional risk associated with the time change is low for a healthy person with no pre-existing cardiovascular risk factors. It is in people who already have known coronary artery disease, poorly controlled hypertension, or other cardiovascular risk factors, that the time change merits particular vigilance - getting enough sleep, avoiding unusual strenuous physical exertion in the first few days, and not overlooking potentially cardiac symptoms such as chest pain or unusual shortness of breath.
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