Agnes MaxwellOn Sunday 29 March 2026 at 1:00 am, the UK clocks spring forward to 2:00 am, marking the start of British Summer Time — and costing every person in the country one hour of sleep. While most people shrug off the change, research shows that losing just sixty minutes can trigger a cascade of health effects lasting far longer than a single groggy Monday morning.
What Actually Happens to Your Body
The human body runs on a circadian rhythm — an internal 24-hour clock that governs sleep, hormone production, alertness, digestion, and mood. When the clock jumps forward, this biological schedule is suddenly misaligned with the outside world. Your body still "thinks" it is 7 am when it is actually 8 am.
According to research published by the University of East London, sleep quality drops by 5 to 15 per cent in the days following the spring clock change, while nighttime movement — a key indicator of disrupted sleep — increases by 10 to 25 per cent. Most people take three to seven days to fully adjust, but night owls and people with existing sleep disorders can take up to two to three weeks to realign their sleep-wake cycles.
Dr Sarah Holloway, a sleep specialist at the Royal College of Physicians, explains: "We underestimate how much the spring transition affects us. Losing one hour is not just tiredness — it disrupts the hormonal cycles that regulate cortisol, melatonin, and heart rate variability."
The Heart Health Connection
Perhaps the most striking finding comes from cardiovascular research. Studies published in the New England Journal of Medicine and referenced by the American Heart Association suggest a link between the spring clock change and a 10 to 24 per cent short-term increase in heart attack risk in the days immediately following the transition — particularly on the Monday after clocks move forward.
The mechanism is well understood: sleep deprivation elevates cortisol levels, increases blood pressure and inflammation, and disrupts the normal 6 am surge in cardiovascular activity that the body normally manages during natural waking. When that surge happens while the body is still in sleep mode — confused by the new clock — the additional strain on the heart is measurable.
It is worth noting that a more recent Duke University study analysing nearly 170,000 patients found no significant population-wide increase in heart attacks around DST transitions. However, health experts emphasise that this does not apply equally to everyone: people with pre-existing cardiovascular conditions, sleep disorders, or high-stress lifestyles remain at elevated risk.
Mental Health and Mood Effects
The spring clock change is also linked to short-term spikes in depressive episodes and irritability. The body's serotonin regulation — closely tied to light exposure and sleep cycles — is temporarily thrown off. The Royal College of Psychiatrists notes that the combination of disrupted sleep and earlier darkness at the start of the day (before the longer evenings compensate) can worsen symptoms in people prone to seasonal affective disorder (SAD) or general anxiety.
In practical terms, this can mean:
- Difficulty concentrating at work on Monday and Tuesday after the change
- Heightened emotional reactivity or irritability
- Disrupted appetite and energy crashes mid-afternoon
- Reduced impulse control and slower reaction times — contributing to the documented spike in road accidents in the 48 hours after the clock change
Who Is Most at Risk?
Not everyone is equally affected. The groups most vulnerable to the negative effects of the spring clock change include:
Night owls: People who naturally sleep late find the transition hardest. Their internal clock is already running behind, and losing an hour makes the misalignment worse.
Shift workers: Those with irregular schedules already have disrupted circadian rhythms. The clock change adds another layer of disruption.
Older adults: Circadian rhythms become less flexible with age. People over 60 may take longer to adjust and feel the cardiovascular effects more acutely.
People with heart conditions: Anyone with a history of hypertension, coronary artery disease, or arrhythmia should speak to their GP if they notice unusual symptoms in the days following the clock change.
Children and teenagers: Young people's sleep needs are greater, and losing an hour can significantly affect school performance and mood during the adjustment period.
Five Steps to Protect Your Health This Weekend
Health professionals recommend a simple protocol to minimise the impact of the spring clock change:
Start adjusting now: Go to bed 15 to 20 minutes earlier each of the two or three nights before Sunday 29 March. This gradual shift helps your body adapt without a sudden shock.
Prioritise light exposure: Daylight is the primary regulator of your circadian clock. Get outside within 30 minutes of waking on Monday to signal to your brain that it is morning.
Avoid alcohol and caffeine after 2 pm: Both interfere with sleep quality and delay your circadian adaptation.
Keep your sleep environment cool and dark: Even though evenings will be lighter, blackout curtains help signal to your body that it is time to sleep.
Move gently: Light exercise on Sunday and Monday — a walk, not an intense run — helps reduce cortisol and promote natural tiredness by bedtime.
When to See a Doctor
Most people adapt to the clock change within a week with minimal lasting impact. However, if you experience any of the following in the days after 29 March, it is worth seeking medical advice:
- Chest tightness, palpitations or shortness of breath, particularly on waking
- Persistent insomnia lasting more than two weeks
- Significant worsening of depressive symptoms or anxiety
- Extreme fatigue that does not improve with sleep
- Dizziness or confusion that is unusual for you
A GP or sleep medicine specialist can assess whether the disruption has triggered or worsened an underlying condition. For people already managing heart health, hypertension, or a sleep disorder, a brief consultation ahead of the clock change is a proactive step that can prevent more serious consequences.
British Summer Time offers longer evenings and more light for outdoor activity — real benefits for physical and mental health. But the transition itself is a physiological stress event. Taking it seriously, just for a few days, can make the difference between a smooth adjustment and a week of unnecessary suffering.
Medical note: This article is for general information only. Always consult a qualified healthcare professional for advice specific to your circumstances, particularly if you have an existing cardiovascular or sleep condition.
